Exhaust hose overheat

[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


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[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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