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air in cooling?

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andyfoxmarine

New member
hey everybody and thanks in advance, ive got a 318 in a twin motor marinette, it overheated so i changed the impellor, i had some problems still yet with overheating, i removed the heads thinking head gasket, one was blown so i removed both heads and sent them to the machine shop, new heads and gaskets now, now with engine all back together im getting air pressure backing back into engine, i removed the muffler to check for blockage-all clear, no blockage in exhaust system or anything, engine is getting awesome raw water but after running about 30 secs it will start making a damn awful howling sound and water will back back into the engine and kill it, what is goin on? im out of ideas!?
 
yeah its rw cooled, i had to replace the impellor since that was the cause of the overheat, and thanks a lot but yeah ive already pressure tested the exhaust and from that test they seem ok, no leaks, but its just the craziest thing, it will make a loud howling sound and then the engine just dies,...timing is dead on, carb is great, no restrictions in the rw lines anywhere,...
 
nah, no water in the cylinders, but i pulled the thermo housing hose off since its the highest point, it was pumping great water and right before the engine started to die their was simontaniously a moment of air in the hose and then water started to gush out of the thermo housing like it was back flowing or something then it dies....
 
If water is, in fact, what's causing the engine to die, it's very odd that there's none in the cylinders and/or oil.

Do you have a strainer on your RW intake? Might want to check for a pre-pump clog. That could cause the hiccups as well as the previous overheating and failed impeller. When a pump is temporarily starved of water, it'll make a pretty nasty sound too.
 
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yeah i actually checked the strainer and had to replace the housing because of a crack in it was pulling a lil bit of air in,...so yeah already went down that road...but no water in the oil or the cylinders, im not sure where it would be but im starting to think its a cracked block,...but then again nothing in the oil.....im stumped
 
if it helps,...at first it acted like the muffler was clogged because the exhaust hoses would swell up, after further inspection the muffler was fine, while i had the muffler off i ran the engine and the hoses swelled again as if there was a lot of backpressure but there was none...
 
Yeah, after reading that last post (about the hoses swelling), I think you’ve definitely got some sort of post-engine obstruction.

Re: the cracked block……if you had one, you’d know it.
 
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It was one of the 3" diameter hoses that failed. The outside looked fine. The inside layer delaminated and created a baloon pocket that would inflate, fill with water and close off the hose when the engine was running and then deflate when the engine was turned off. The inner layer of the hose is softer and more pliable rubber than the outer covering.
 

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Wow! That's one for the old Keeper File. With your permission, I'm going to post that photo on the Marinette web site.

Jeff
 
i cant thank u guys enough! it was a piece of the exhaust post engine but pre muffler...which would explain why i didnt see it collapsed when i checked the muffler...got the piece on order 2day and ill be cruising this weekend! thanks a lot!
 
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