Exhaust hose overheat

[SquamInboards]

I'm cross-posting this here, I had been following a couple threads on CCFan about this topic and I thought I'd see what you guys think. I thought I posted this here when I had the problem, but I couldn't find the thread. So here goes.

My boat does a lot of idling, often for night cruising when it's chilly, so we don't want to go fast. Now I've started taking my son for "boat naps" where he sleeps while I drive around the lake (he's almost 2 years old), but again, more idling. Last weekend it was over 3 hours straight.

The problem I had two years ago (and now again) was the exhaust hoses were getting extremely hot, like 250-300 F (they are rated for 250 F). To be clear, we're talking about the 3 1/2" ID hoses that connect the risers to the steel elbows that are in the floor of the boat.

I narrowed it down to an internally collapsing hose, which was preventing water from escaping the riser and cooling the hoses at low speed. At higher RPM the water was forced through, so cooling was no problem. It was worse on one side, and I was sure I had found the culprit because the problem followed the hose when I switched sides. So I replaced the hoses and had no problems thereafter. That is, I checked them multiple times that summer after long idling periods, and they were fine (under 200 degrees at all times). I don't think I even thought about the problem last year, since I had no symptoms.

I was out in the boat this weekend and noticed the hoses getting hot again at idle (I smelled burning rubber in the exhaust fumes), but no problem at speed. The risers are normal temps, all the time - never over 160. I think that because I do a lot of prolonged idling, the hoses get a little too hot over time, and break down around (basically melt into) the channels that allow water to pass from the risers to the hoses. Then the problem is self-perpetuating, as less and less water passes through at lower speeds, and the hoses get worse over time. The engine temp is always dead on normal, and I've cleaned out my manifolds and risers, there's no flow issue in there, I'm certain of it.

I don't think there's a back pressure issue, because the engine always runs flawlessly, and plenty of water comes out the exhaust when I run it on the trailer. The problem is the same on both sides, and my boat has full dual exhausts. The problem went away COMPLETELY with the new hoses, and has slowly returned.

Since the hoses get hot, but never more than 300, I am going to put the higher-temp silicone exhaust hose (rated for 350F) in place of the old stuff, since I now have to replace it anyway, and hopefully that will be the end of it. I hate to mask the problem with higher-tolerance materials, but I genuinely think there is no design issue, and no water flow issue, it's just that when you idle for SO LONG, it slowly weakens and collapses the inside of the hoses, until they get less and less water through the channels, and it's downhill from there.

Anyone have thoughts on this? Am I crazy?

[TitanTn]

I don't think you're crazy. I don't do the same amount of idling as you do, but my hoses are only about 3 years old and I've noticed that they started to droop on the inside from what looks like excessive heat. I'm still doing okay, but they obviously won't last too many more years as they seem to be on the fringe of tolerating normal heat loads. I follow your line of reasoning that your extended period of idling is not running the expected amount of cool water through the hoses and the heat is eating them away. And thus I think your proposed solution is a good one - I mean the alternative is to replace your hoses every year with the factory type of hose - so what's the difference? You're not going to do anything different to the engine because the block and the manifolds are within the expected temp range.

[SquamInboards]

the alternative is to replace your hoses every year with the factory type of hose - so what's the difference?

I think this is the final straw for me - I have to replace the hoses I have. So why not spend a little more on hoses that might last longer? I have a very healthy cooling system with no leaks or clogs that I can find. I've never cooked an impeller in this engine and I've cleaned the manifolds and risers thoroughly so there shouldn't be any blockage. The engine and all its parts run at normal temps. Except those hoses, after long periods of idling.

I will also TRY not to idle for such long periods, I'm sure it's not the best thing for the engine. But sometimes, you gotta use the machine the way you want, and it should just do whatever you ask of it.

[CJD]

This is an interesting condition. I wonder if it isn't less a problem of the amount of heat, but rather poor distribution of the cooling water in the riser at low speeds. Like, possibly, the water collects at the bottom, so the top of the hose overheats? If that's the case, the higher temp hose would be the solution, as you are not going to be able to increase the water flow while idling.

[SquamInboards]

I wondered that too, although the way the riser gasket has a port blocked on the side nearest the bottom of the hose, it's intended to force water up and over the top of the riser, which it seems to; the top of the riser is cool enough. BUT the way the connection of the riser to the hose is designed, water could certainly favor the bottom, and then of course no matter how it enters the hose it will favor the bottom, especially lower down on the hose. I never thought to check the temp separately on the bottom side of the hose.

If money were no object, I'd be using silicone junctions between the risers and a section of pipe, rather than the hoses. But getting two sections of stainless pipe made up seems rather prohibitive. The pipe would have to include a reduction to 3" diameter, because the pipes in the floor are 3", while the engine has 3 1/2" output. Right now I use the reducers that PCM sells, and two sections of hose. The 3 1/2" hose is by far the longer section.

Hey, maybe there is back pressure caused by the reduction? But if that's the problem, then the solution is ripping up my entire rear floor and putting in new exhausts through the transom. Which will no doubt lead to a complete floor rip-up and therefore new stringers. Yeah... not this year.

[92SupraComp]

you can buy the 3" outlet risers. They bolt right up to the same manifold. Also, for our CC, they had TIGHT bends with the 3" wire reinforced hose and it got overheated and collapsed. I replaced it with 4 sections of 3" non-reinforced hose and 4 3" stainless steel 90* elbows off ebay. The SS elbows were only a $100 free shipping! :D Looks sweet under the hood and runs like a top again.

[SquamInboards]

you can buy the 3" outlet risers. They bolt right up to the same manifold

Wow. Where was that idea 5 years ago when we swapped in the newer engine? I even HAD some of those risers, literally laying around, from other similar engines. How did we not think of that??

[92SupraComp]

Are you being sarcastic or no? Because the exhaust manifolds are identical. Only the risers are different in H.O. applications...

Base/Powerplus: 3" riser with long runner, mixes wet and exhaust really well

H.O.: 3.5" riser outlet, short runner, better exhaust vapor flow, does not mix water and exhaust as well...

Below, PIC 1 is a HO riser, PIC 2 is base/powerplus riser

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[SquamInboards]

Are you being sarcastic or no? Because the exhaust manifolds are identical.

Haha, sorry! No sarcasm at all, seriously! Stupid internetz and their lack of expressible TONE.

When you said that about the riser, a little light went off in my head. When we put that engine in a few years ago, it wasn't until we were almost water-ready when we discovered/realized the exhausts were different diameter (duh). If we had realized RIGHT THEN that we could just bolt on different risers, it would have saved many hose clamps, some swearing, and at least one long round trip to the only place around that actually stocks 3.5" exhaust hose in any real volume, oh yeah and overnight shipping on some reducers since no local shop had anything that would work. I think I would have been better off with the other riser from day 1! Maybe the hoses wouldn't even be overheating right now.

You should have seen our late-night attempts to make the exhaust work without the proper reducers. I didn't take pictures for a reason.

[SquamInboards]

So I put the VHT (Very High Temp - 350F rated) silicone hoses on last week. Weird stuff, VERY flexible, I could fold a 3' section in half with one hand. Anyone who has handled the wire-reinforced normal exhaust hose knows why that is so bizarre. On the other hand, it was easy to install! The hardest part was getting it in a straight run, with (almost) no kinks. It was impossible to get perfect - one side is basically perfect, the other side has a maybe 1/2" deep kink at the very bottom. They do make wire-reinforced silicone hose, but it's so close to straight I didn't bother. Plus I could get just 3' of the regular stuff, but had to get a 12' section of the wired variety. No thanks, at $67/foot.

I ran the boat a bunch this weekend, and the hoses did fine, although I haven't done an extended idling temp check. They jiggle a little at idle because they're so flexible, it's weird. But anyway, I am hoping these hoses will not have any issue if they DO get up to 250+ for a while. Strange stuff, although nice to work with. I could cut it with my pocket knife, easily. I'll post a picture when I get a chance, I forgot to take one this weekend.

This is the stuff: (image credit: great lakes skipper - ebay)
http://greatlakesskipper.com/media/catalog/product/cache/1/thumbnail/9df78eab33525d08d6e5fb8d27136e95/9/7/9742-1-lg.jpg

[TitanTn]

I'm thinking this will work. It doesn't matter how stiff it is as long as it doesn't collapse and the run is so straight that I think you'll be fine. Keep us updated.

[SquamInboards]

End-of-season update:

The silicone hose DID perform as promised, and didn't melt. However, surprise, surprise... it still gets hot. I have completely gone through the cooling system in this boat already in 2012. I'm not doing it again and I'm just leaving the silicone hose as-is. When I inevitably do stringers, I might have some SS pipes made to eliminate the bend in the hoses. MAYBE then I'll go through the system again for good measure. But I also have 2 kids now, so basically if it ain't broke don't fix it.

[Cusefan78]

Could it be the water is having a hard time escaping out the back of the boat cause your moving idling. Maybe there's isn't enough pressure to push the water out the exhaust flaps. If that's the case maybe your circulation pump maybe going bad or the impeller is going bad. Something isn't right. I used the silicone non wired hoses this year and they do get warm but I can leave my hand on them and not get burned. I'm thinking it's a circulation problem.

[SquamInboards]

It's not an issue with the impeller, that's been replaced every year and hasn't changed the condition. I do wonder about backpressure, although there doesn't appear to be any issue with flow on that side, with a few tests I've done. Granted, the conditions are different but it pours water out both exhausts equally when running on the trailer. Also, I replaced the hoses with the boat in the water and if you tilted the boat to one side, water poured in through the open exhaust pipe fitting at the floor... equally on both sides, depending on how you tilted the boat. Hardly scientific tests, but I'm not sure how else I'd really test the system between the pipe where it enters the floor, and where it exits the transom.

What's most bothersome is that it's worse on the starboard side. I was sure it was a problem with the hose itself because at one point I switched the hoses and the problem went to the other side (followed the hose, indicating a bad hose). But that theory is out the window now, especially since the silicone hose gets hot only on the starboard side. Now I wonder if that manifold is more prone to rust-debris-accumulation? I could take it off again and clean it all out...

[Jetlink]

Seeing as how you are more at low engine speed when running the boat, I wonder if changing the diameter of the pulley on the raw water pump to make it run slightly faster to increase water flow at low engine speeds to make it behave like the engine is running faster might help.

[chris young]

I dunno about that one. When I put my intake into a 5 gallon bucket at idle, it empties it in about 20 seconds, that's a lot of water at idle. Additionally, you'd be pumping more water at higher rpms.

[Blackntan90]

What about running the bilge blowers? You are supposed to run them at idle speed, and every one does it- right? But maybe a little more airflow could reduce the dog house temps, and in turn the exhaust might not be such an issue at idle...just a thought.

[lively]

Touch your risers and see if they are hot at idle at first start up and then to operating temp . Timing could have play here as well and heat range in plugs . You need to verify that they are in fact the right ones


Sent from my iPhone using Tapatalk

[SquamInboards]

Seeing as how you are more at low engine speed when running the boat, I wonder if changing the diameter of the pulley on the raw water pump to make it run slightly faster to increase water flow at low engine speeds to make it behave like the engine is running faster might help.

I think overall water flow isn't the problem, since it's now isolated to the starboard side.


What about running the bilge blowers? You are supposed to run them at idle speed, and every one does it- right? But maybe a little more airflow could reduce the dog house temps, and in turn the exhaust might not be such an issue at idle...just a thought.

hmm what are these blowers you speak of?? Just kidding. Sort of. I haven't run those in years, I know, I know boats blow up all the time because of fumes... of course with EFI you don't have the same degree of vapors escaping from the carb... but I know I should run a blower. However in this case I don't think it would make the difference.


Touch your risers and see if they are hot at idle at first start up and then to operating temp . Timing could have play here as well and heat range in plugs . You need to verify that they are in fact the right ones



I've checked the risers, although not recently, but this spring when I was replacing the hoses they would run fairly normal temps like <150 F, even when the starboard hose got warmer. This is partly why I thought the hose itself was the issue, since the riser wasn't overly hot. It does get a little warmer after a long time, but it's really the hose that gets hot.

The plugs are the standard autolite 764. I haven't checked timing in a while, but there again, the engine temp is fine, and verified with a laser IR thermometer, it's ok throughout the engine - not just at the sensor.

The cooling system is just too simple on these engines, I'm leaning toward a rust-flake-clogged starboard manifold. In fact, I might hunt down another manifold and try swapping it out next season for a different one. At least with the silicone hose, it won't be that hard to change out! Or at the very least, I should take it off and flush the hell out of it, again.


Thanks for all the ideas, I do appreciate the thought you guys are putting into this. More angles and fresh ideas are always welcome. Unfortunately I think I will winterize the boat this week or next because I can really only use it on weekends right now, and this is the best time of year for hiking, in my opinion. I'll keep this thread updated if I make any progress. The parts guy at the marina where I got the crazy silicone hose asks me about it every time I see him, and it reminds me that I've managed only to mask the problem...

[lively]

Ok , is your boat trailered ? If it is can you run it on the hose in the driveway ? If so you can see how much water is coming out of the pipes , then add more water pressure and check you hoses again . Once you see the temp you like then look at testing GPH output from your raw water pick up . They are rated differently for different applications . And the internal impeller housing is meant to wear with the rubber impeller "together" although impeller goes first the housing still wears over time . Touch the back of the raw water pump and is it cool / warm / hot ? Think about it water is sucked up by that pump and pushed into engine and out . How much water is actually getting sucked up ? Do the bucket test .


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[SquamInboards]

The boat is only ever on its trailer for the winter, and this winter it won't be stored on its trailer unfortunately. I agree that running it on a hose and measuring water output on each side - not just guessing but actually measuring - is an exercise worth doing, although probably in the spring at this point.

The RWP housing runs extremely close to the temp of the lake, I've checked it with my IR thermometer. And when I winterize it, I sort of do the "bucket test" when I suck up antifreeze... but there again I should *measure* the time it takes, which I never have.

Thanks again for the thoughts and ideas. I think I just need to be a little more methodical about this, rather than assuming something is OK because it "kinda seems normal."

The good news is, I had a whole season without a single hiccup with the boat, over 60 hours and the only "issue" I had was re-packing the stuffing box (which was by choice). Oh and the Keel Guard is delaminating, not from the boat, but from itself. That I can live with, if it's my only problem this season.

[SquamInboards]

Update: I'm not entirely surprised, but last night the silicone hose failed. We went out for a late-season night cruise, and of course we were just idling for probably close to an hour, when suddenly the exhaust makes a much louder sound. It's clearly the sound of exhaust dumping out under the engine cover, and I shut the engine off right away. When I opened the engine cover, there was nothing visible, and no extra water anywhere. A quick look around revealed the starboard side hose completely SPLIT down the side, along the length of the hose over a span of about 8 inches. The fact that it wasn't spewing water out means, of course, there wasn't much, if any, going down that side.

I was able to wrap some webbing around the hose to sort of keep it together, then move a hose clamp and use another strap I had to keep the webbing in place, just enough to get home. I ran at a speed just above idle to keep water flow going, but not any faster so as not to put excess strain on the rest of the hose - or to fill the bilge with exhaust water.

I still don't think this is a water flow problem before the manifold, but rather an issue later in the system, possibly a partial blockage in the muffler. The reason I think this is because I have addressed all possible water flow issues in past years with the system leading up to the manifolds. I don't know who it was on this forum who had the problem recently, but someone who had redone their floors had a similar problem and found the muffler to be the culprit. The fact that the issue stays on the starboard side only is more evidence that it's not a water supply problem.

My dilemma now is what to do with the boat at this point. The floor is absolutely solid. The motor mounts are... pretty solid. But I know it's all original, and we all know what that means. I love the boat but it's not my dream to own it forever. I have money set aside for a new boat, but I'd have to sell this one. I will be sleeping on this, but I'm tempted to take this as the reason to rip up the floor and replace everything from the front seats to the transom - I'm sure there is some water-soaked foam, if not much rotten wood yet. I've seen plenty of boats that were caught early - before there were any major signs of rot - and didn't need a full bow-to-stern gut. I'm just terrified to go down that road because I know where it usually goes.

Or should I just get another 3' section of VHT silicone hose for $150 and remember to bump up the RPMs a little more?

See my handy band-aid fix to get the boat home without massive noise and/or water filling the bilge. It wasn't bad actually - you could hardly hear the difference!

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[wotan2525]

The only thing that repair is missing is zip ties!

Glad you were able to make it home. I don't have any great ideas about the problem (my boat never had mufflers) but if it was me, I'd definitely want to take the steps to fix it rather than just band-aid it.

[Jetlink]

That was me you're thinking about with the exhaust overheating the hose aft/downstream from the riser and manifold. What is after your hose there between the riser and the transom outlet?

[SquamInboards]

That was me you're thinking about with the exhaust overheating the hose aft/downstream from the riser and manifold. What is after your hose there between the riser and the transom outlet?

That's right, now it sounds familiar.

After the hose it's a stainless 3" pipe that goes into the floor at about a 45, then I presume there's a muffler between there and the transom pipe which has just a rubber flapper (no Super Trapp or anything like that).

I'm betting something is blocking flow in that starboard muffler.

What worries me about "fixing it right" is taking the floor up in this boat... I don't think I want to get into a cap-off resto right now.

[Jetlink]

Have you checked flow through the manifolds and risers? I forget, is it only on one side like mine that has an issue? If you have a "fish" that you can run down the exhaust when you take the damaged hose off see if it has any obstructions before it exits the transom. My issue was I had something that created enough of a blockage to increase back pressure that forced the water to take the path of least resistance and I bet that is what is happening here.

[wotan2525]

Have you checked flow through the manifolds and risers? I forget, is it only on one side like mine that has an issue? If you have a "fish" that you can run down the exhaust when you take the damaged hose off see if it has any obstructions before it exits the transom. My issue was I had something that created enough of a blockage to increase back pressure that forced the water to take the path of least resistance and I bet that is what is happening here.

I don't think this is the issue. If the blockage was after the manifold/riser than there would have been plenty of water coming through the split in the exhaust hose. I'd stick a garden hose in there and make sure you get a steady stream of water out the back of the boat.

Have these manifolds ever been off? Any chance the gaskets were installed incorrectly on that side? (I once reassembled an engine and didn't install a head gasket on one side!!)

[SquamInboards]

Have you checked flow through the manifolds and risers? I forget, is it only on one side like mine that has an issue? If you have a "fish" that you can run down the exhaust when you take the damaged hose off see if it has any obstructions before it exits the transom. My issue was I had something that created enough of a blockage to increase back pressure that forced the water to take the path of least resistance and I bet that is what is happening here.

The problem is really only starboard side. The port side is more or less fine. I think I may have the same issue with having a small/partial blockage in the muffler, as you said. The rest of the system has been gone through.


I don't think this is the issue. If the blockage was after the manifold/riser than there would have been plenty of water coming through the split in the exhaust hose. I'd stick a garden hose in there and make sure you get a steady stream of water out the back of the boat.

Have these manifolds ever been off? Any chance the gaskets were installed incorrectly on that side? (I once reassembled an engine and didn't install a head gasket on one side!!)

I haven't tested this scientifically, by putting a bucket under each side and measuring / seeing if one fills up faster than the other. I can tell you water comes out both sides when the boat is out of the water, and water flows out fine above idle. It's the extended idle times that seems to cause problems. On the gasket - yes, the risers / manifolds have been off, and I'm 100% positive the gaskets are correct. That was a plausible early theory but unfortunately it wasn't the issue.

The fact that it's really only on one side, too, makes me believe it's something about that muffler on that side. I've had the hoses off where they connect to the manifolds, and both put out good flow. I've had the manifolds and risers completely apart and flushed out thoroughly. I've ground out the grooves in the riser where the hose slips over to let more water out.

But man, I'm terrified to rip up the floor......

[SquamInboards]

If you have a "fish" that you can run down the exhaust when you take the damaged hose off see if it has any obstructions before it exits the transom.

I don't know what the muffler looks like internally. Could you fish some kind of stiff wire (like one of those tools you use to pull wires/cables through walls, etc) straight through from the inside to the outside? Or are there baffles in the way?

When I replaced the hoses last, I did it in the water. My friend who helped me was amused that if we both stood on one side of the boat, water flowed in at an alarming rate through the 3" pipe... however we did note that water flowed in about the same from each side. Which makes sense because water flows out fine at higher engine speeds. It kind of adds up that at low engine speeds, there is some back pressure created in the system and it wouldn't take a lot of restriction to keep the cooling water passages from putting out their usual flow. A small amount might just be trickling down the bottom side of the hose, while the rest just goes out the other side - the path of least resistance as you said.

Can you tell this issue is driving me crazy? It's been lingering for about 4 years, since I first burned through an exhaust hose. I worked at a marina at the time and had many mechanical minds thinking about it. I did everything we would have done if a customer had been having the same issue. At this point, I'm not sure what I'd tell a customer in the same situation. Except don't idle for so long... which isn't what I want to hear. That's like, "oh yes your car will do that after going 30mph for more than 15 minutes continuously, you have to just change your driving style..." what? It's not like I'm experiencing an issue after running WOT for long periods.

[wotan2525]

I'm also stumped. My biggest fear? You tear up your floor and don't even find mufflers there.

[SquamInboards]

I'm also stumped. My biggest fear? You tear up your floor and don't even find mufflers there.

Ha! It's not loud enough to be straight-piped. But I hear you. That might kill me.

[chris young]

Someone here has to know, but my understanding is that these boats are straight piped and that the riser is what makes it quieter than if it were just straight pipes on a header or regular non marine manifold. I know that there is a Nautique at our club lake with the exact same motor as in my Rider, and it sounds much nicer, and it does have the muffler in the dog house.

[ngavchris]

Can you not just look up the exhaust pipes from the back of the boat. My brothers 83 Rider is straight piped. Worst case go to Home Depot and buy a wall camera. We use them and work and they would allow you to look from the engine side.
Good luck.....

[TitanTn]

Tearing up the floor really isn't that big of a job and just because you do it - you don't have to do a cap off restoration. I would consider cutting out a small section of floor over the area where the muffler is and figure out the issue. Replacing the small section of floor will be quick and easy.

[Jetlink]

Take the bad hose off the starboard side, set a light to shine down the 45 degree angle pipe before it runs under the floor. Go see if you can see a decent amount of light through the transom outlet. If no, then there are probably baffle in there forming a muffler of some sorts. As for the floor part, I ended up cutting out my floor again to allow access to both mufflers after I was stupid and did not allow for that the first time doing my restoration. I dropped my boat off at the winter storage today and will not be seeing it again until April next year but I will gladly help in any way I can.

As for the going insane comment and being stumped. We had every boat mechanic in the area and even Vince at SkiDim stumped and grasping at straws on mine. As soon as I looked at the port transom outlet I knew something wasn't right. As soon as I cut out the floor and removed the port muffler, my overheat issue was eliminated. There are ways to test various theories. My testing prior to that had me running the boat with 5 gallon buckets behind the risers to catch water and both filled up almost evenly. With the whole system together with the bad muffler there the disparity between the two on a volume level was more noticeable but not alarming. I was amazed at how just a small amount of increased back pressure on one side of the exhaust sent so much water to the other side because that offered a path of least resistance.

[Blackntan90]

My 2 cents...I once took a flashlight and looked up my exhaust from the transom to see what was in there. I saw a series of 'baffles' that alternated, 1 from the bottom and 1 from the top- so on all the way as far as I could see. Now this is on a 1990 Mariah with the 351. I too have the 45 degree angled pipe going under the rear floor. And after reading this, noticed one of my exhaust hoses looks like it could be getting hot- we also do a lot of idle speed cruising- miles at a time. I have been thinking about doing the stainless pipe section in place of the hoses you mentioned.

[NoWake]

This boat has been begging you for four years to pull up a couple sections of flooring. At least now you say to yourself... "I just had to":o. It will give you peace of mind. Good luck

[SquamInboards]

Someone here has to know, but my understanding is that these boats are straight piped and that the riser is what makes it quieter than if it were just straight pipes on a header or regular non marine manifold. I know that there is a Nautique at our club lake with the exact same motor as in my Rider, and it sounds much nicer, and it does have the muffler in the dog house.

I believe there's some sort of baffle/muffler structure in there because my boat is a good bit quieter than a couple others I'm familiar with, two that I know for a fact are straight-piped. It's not a huge difference, but it's there.


Can you not just look up the exhaust pipes from the back of the boat. My brothers 83 Rider is straight piped. Worst case go to Home Depot and buy a wall camera. We use them and work and they would allow you to look from the engine side.
Good luck.....

I'll certainly try this when I get the boat out of the water, probably this weekend. At least looking with a bright flashlight and/or trying to fish something through from the exhaust output.


Tearing up the floor really isn't that big of a job and just because you do it - you don't have to do a cap off restoration. I would consider cutting out a small section of floor over the area where the muffler is and figure out the issue. Replacing the small section of floor will be quick and easy.

Another issue for me is the rear seats in the Bravura/Mariah are framed out in fiberglass that's part of the cap. So, access under those seats isn't easy, short of cutting out sections of the seat structure. It's not like the comp that has a totally independent rear seat...


My 2 cents...I once took a flashlight and looked up my exhaust from the transom to see what was in there. I saw a series of 'baffles' that alternated, 1 from the bottom and 1 from the top- so on all the way as far as I could see. Now this is on a 1990 Mariah with the 351. I too have the 45 degree angled pipe going under the rear floor. And after reading this, noticed one of my exhaust hoses looks like it could be getting hot- we also do a lot of idle speed cruising- miles at a time. I have been thinking about doing the stainless pipe section in place of the hoses you mentioned.

That's very interesting, being that the 1990 Mariah is basically the same as my boat but with bow seats. I suspect my exhaust structure is the same as yours. AND very interesting that you have an exhaust hose getting warm.

I've thought about stainless pipes, but you still have to join the pipes to the riser and the floor pipe, AND the pipe could get really hot and melt the carpet on the engine cover - it melted it on mine, right through the silicone hose.


This boat has been begging you for four years to pull up a couple sections of flooring. At least now you say to yourself... "I just had to":o. It will give you peace of mind. Good luck

Yeah, I know. I need to look at the rear floor very closely and see how impossible it would really be. The biggest issue, as I mentioned, is the rear seat structure being a part of the cap. This also makes it really hard to get the fuel tank out. It's too big to lift straight up and out of the hole that the ski locker uses. Believe me, I spent hours trying.

[SquamInboards]

Thanks for all the replies on this. I'm probably pulling the boat this coming weekend, at which point I'll weigh my options. I should probably just order a new hose anyway, because I will need that no matter what.

Also, I've got enough in my boat savings fund to look seriously at a newer boat in the $15-20k range, and I've wanted a v-drive for a long time... or at least a bowrider. Hmm. Not that this particular nit-picking issue is a reason on its own to sell the boat, but I've been casually looking for several years. This boat has been great, and I always like to sell my stuff when it's working well with no major issues. This boat definitely meets that standard, if maybe you can't idle for more than an hour continuously.