Stupid engine rebuild

So I thought everything was fine. Wrong.

Started at the lake, ran like butter at the ramp. Drove about 5 minutes away and turned it off. Floated for about 5 minutes and tried to recrank. Turned over for a few seconds and then stopped. Couldn't get it to turn over anymore. Pulled the plugs and the cylinders are full of water. The oil is pristine. The water is in all cylinders, but mainly in the front two on each side. After clearing most of the water it never seemed to completely get it all, kinda like it was still entering however it's getting in.

Any ideas?

For those that haven't been following my story, the engine was rebuilt this winter. The block and heads have been fluxed. New guides and seats. Valve job. All new bottom end. New gaskets. 22 hours on the rebuild.

This might be a stupid question, but did you do anything different with the exhaust?

First thing I think I would check is the manifold to riser gaskets for leaks.

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Originally Posted by supraaddict

This might be a stupid question, but did you do anything different with the exhaust?

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There are no dumb questions. Just a dumb boat that I'm sick of wrenching on. No, I didn't do anything different with the exhaust. The manifolds are somewhere around 6 years old I'm guessing. The previous owner bought them, so I don't know exactly.

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Originally Posted by ssa

First thing I think I would check is the manifold to riser gaskets for leaks.

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I did a visual inspection when I had them off this winter and cleaned them out. They're not that old, and because this is happening to ALL cylinders I don't think I've had a failure on both manifolds at exactly the same time. I'm wondering if it's the intake in some way.

Check the intake manifold. Did you have the heads milled?

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Originally Posted by michael hunter

Check the intake manifold. Did you have the heads milled?

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I'm walking down to the barn right now to pull the intake manifold. I'm not sure if damage will be visible to the eye or if I'll have to get it tested somehow. And yes, the heads were milled.

Odd for both manifolds or risers to fail at the same time, and I'd imagine given the angle of the engine it would be more likely to fill the cylinders towards the rear rather than the front. It's possible it could be intake leaking coolant passages to adjacent intake ports, though unlikely as it would likely leak into the valley and oil as well. Possible though. Did you RTV around the coolant passages on the intake gaskets? Even on hard to seal intakes with shaved heads I've never had coolant leak, though have had vacuum leaks.

I'd say head gaskets more likely. Try a compression test it may give some insight, though maybe not. I did head gaskets on a SBF a few weeks ago and compression numbers were good but couldn't explain an overheating problem so figured it was worth a look and had two cyls identical compression right next to each other. One cyl on the opposite bank has blown through to a coolant passage. Compression was good, plug and chamber looked normal, engine ran fine. Must have been minor, but it the gasket had failed. Just a thought. You could put air in the cylinders getting water and see if you can feel/hear air coming through the cooling system.

Still sounds more like cracked or rusted through manifolds and risers, or possibly failed manifold to riser gaskets, given water in all cyls. Another possibility is reversion. Since this is a fresh build what cam are you running? Too much overlap can pull water back into the dry part of manifold and into the cylinders at idle and low RPM unless you've got taller risers, water introduced farther back, etc...

22 hours on the engine, has it had any of these issues previously or just starting now with nothing changed?

Intake manifold gaskets or head gaskets , you can verify this by doing a leak down at the t-stat housing and plugging the exhaust and circulating pump . But my guess would be the intake or head gasket . Don't get frustrated stay sharp and diagnose the issue


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Thanks guys. I'm just having a hard time thinking it's head gaskets or manifolds since it's both sides at the same time. If it was just one bank of cylinders I'd be checking manifolds and then head gasket. But this is both sides in equal amounts at the same time. Other than boring .30 over, everything is stock (cam, etc).

I've pulled the intake, and while nothing jumped out at me as the culprit, I'm taking it to a machine shop today for testing. I'm assuming they can test an intake somehow.

This is most definitely outside any personal expertise on my part, but I do remember reading something about the head gaskets on these motors being very easy to put on backwards. IIRC though the symptom was overheating on some cylinders, but it may be worth a look.

Sorry to hear about your issues, doing a rebuild should get you a better motor, not the other way round.

Good luck

I'm just trying to spit-ball here but on my rebuild, there were different headgaskets available and some of them had some cooling ports blocked off. Are you certain that you used the correct ones?

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Originally Posted by wotan2525

I'm just trying to spit-ball here but on my rebuild, there were different headgaskets available and some of them had some cooling ports blocked off. Are you certain that you used the correct ones?

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Great question, and no, I'm not 100% positive, but I tried to watch that as I was assembling. But with 22 hours on the rebuild, I've not had once instance of overheating even slightly. I would think I'd see the temp rise and lower slightly with the opening and closing of the thermostat if it were fluctuating.

I actually just got back from the machine shop and I think they figured it out. It's simple, so I'm embarrassed to say it hadn't occurred to me. I've let the issue of all 8 cylinders being full of water to make me think it's not exhaust manifolds or head gaskets because why would both sides fail at once? But actually the intake manifold is just a pass through from one side to the other. So if an exhaust manifold failed, it would fill up the pistons on both sides of the engine. So I very likely had an exhaust manifold fail and it filled all 8 cylinders with water. So now I'm going to pull the manifolds and do some testing. But I really think this is it.

Interesting. Exhaust was the only thing I could think of, but I agreed with everyone else about the low chance of both sides failing. What you say makes sense, though.

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Originally Posted by TitanTn

There are no dumb questions. Just a dumb boat that I'm sick of wrenching on. No, I didn't do anything different with the exhaust. The manifolds are somewhere around 6 years old I'm guessing. The previous owner bought them, so I don't know exactly.

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The reason I asked the question is in your OP you stated that you were motoring on the lake just fine and when you shut the engine off it wouldn't restart because the cylinders were full of water. The only time this ever happened to me was when a hose came off for the main water inlet on my engine and my engine temp started rising rapidly, I instantly grabbed the throttle and shut her down. I reattached the hose, let the temp come down to 130 and tried to start her back up. The engine wouldn't crank and same thing... water in the front cylinders. Had the boat towed, got her on the trailer, pulled her out of the water and instantly noticed that the exhaust flaps were melted off. So obviously when the temp started rising and l pulled off the throttle and shut off the key, there were no exhaust flaps to hold back the water and in turn filled the cylinders up with water. Pulled all the plugs cranked her over and over, fogged the cylinders, replaced plugs and wires and she started right up. Compression test good and let her run for about 45 minutes to ensure that the cylinder walls did not rust. Everything seems to be good now (Replaced the Exhaust Flaps as well). Might not be your issue but just trying to give you other possibilities in case something may have changed on your boat.

Thanks Brad. Unfortunately I don't have flaps, I have supertrapps, so I don't think this could happen to me. I had been idling for about a minute before I turned it off, so there was no opportunity for water to come back anyway.

I pulled the exhaust manifolds off tonight. I hooked a hose to the water inlet side and turned it on. Water filled the manifold jackets and came out the exhaust side as expected. Nothing leaked back into the exhaust gases side. Did I not test this right? Is it possible that it'll leak badly when it's hot, but not when cold? I'm so disappointed that the issue wasn't obvious. Anyone ever make a tool to remove the riser from the manifold? What now?

Based on this article - http://www.boatus.com/seaworthy/swbtob.asp

I think it could still be the manifolds. I don't know how old they are, and I've had the boat for 4 years. Even if they're not completely at fault, I will likely need to change them soon anyway. I think I'm going to bite the bullet and replace the manifolds and risers now. I'll be sick if that doesn't fix it, but I just don't know what else it could be.

Just a heads up if you do end up getting new manifolds. Whatever it is PCM paints theirs with isnt high temp resistant. I replaced mine this spring and when I took it out for the first time to check everything out since I'd had all the running gear out of it over the winter I got a nice surprise. About 5 minutes out of the no wake zone I could smell something burning. I started looking around and couldn't see anything around the lake it was coming from and thought theres not anything in the front of the boat to catch fire and if its coming from behind me and I'm smelling it running 30 this isnt good. So I stop open the engine cover and smoke is rolling out. My little girl says are we going to sink right here in the middle of the lake. Lol. Anyways it was burning the paint off the runners before they enter the water cooled section. Took about 30 min before it all came off. I'd ran it about a hour in the driveway without it affecting it.

So I spoke with Vince from skidim.com today and I was fully ready to purchase some manifolds. For those that don't know, Vince is a master at inboard ski boats and is a tremendous resource for us. Based on the water being in all 8 cylinders and that the manifolds passed my test, he's convinced that the manifolds aren't the problem. We went through many different scenarios and couldn't come up with anything plausible. His final recommendation was to reassemble everything and do some testing on the hose, and then at the lake. So I've got everything reassembled as of tonight.

I just don't see how both banks of cylinders could get water without it being some kind of ingestion/sucking water up the risers. If so, what caused it? I have no idea. So this is where I am. No where new. I'll be testing on the hose tomorrow afternoon and go from there.

Hey Rob how are you doing with this? Any headway?

Did you recently fill up your boat with fuel? Could be water in the gas...

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Originally Posted by inair

Hey Rob how are you doing with this? Any headway?

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Thanks Ken. I was going to give an update, but I couldn't find this thread. Things are going a little better for now. The manifolds tested fine and I simply couldn't find anything wrong with anything. I put everything back together and tested this weekend. It ran great. No issues with water in the cylinders. No water in the oil. No overheating. I tested compression and it's solid all the way around. My only issue left is hard starting after being warm. I'm hoping that's just some carb adjustments, but we'll see.

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Originally Posted by Zim

Did you recently fill up your boat with fuel? Could be water in the gas...

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I think I'm good there. I've been through several tanks this spring while doing all of the break in and setup. I'm somewhere around 25 hours on the rebuild.

Just out of curiosity, what is your compression on a fresh rebuild?

Averaging about 140 cold, with no oil. Warmed up it should get a little higher.