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Mercruiser 898 overheating

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racer47v

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"I have acquired a 77 20ft sea

"I have acquired a 77 20ft searay with 898 mercruiser 305chevy, Has had several problems causing overheating, Hopefully down to the last one. It overheats above 3300rpm and at low power but not on plane. Motor sounds and runs strong, Will cruise all day at 3000rpm, Complete impeller has been changed,Leak down completed, any suggestions for my winter tear down, sure would this problem gone in the spring when fishing starts
Thanks"
 
"Have you checked/replaced you

"Have you checked/replaced your T'stat? Is is FWC?
If so, the exchanger may need cleaning if she has been used much in salt water."
 
"Tried running it without the

"Tried running it without the Tstat, No help, Boat has never seen salt water, Still may be the Heat exchangers, Any good way to clean / Inspect them without removing them?? Exhaust manifold bolts are never friendly to remove
Thanks"
 
I could be mistaken but I thou

I could be mistaken but I thought the 898 had a 351 ford engine. The 228 is the 305 chevy.

We once had a 888 the ford 302 that did the same thing.
Just started running hot while pulling a skier one day.
The guy replaced the whole engine(block cracked after running it hot to long) the manifolds Y pipe of course the water pumps you name it and it still ran hot. Pumped all kinds of water everything seemed as it should be. Ran fine up to 26-2800rpm.

No one could find anything wrong.
Factory guy's were stumped as well as all the old fart's around the country not just the state.
We have many very well trained and well seasoned mechanics around here to say the least.
The guy spent all summer on this deal.
I mean EVERYTHING was done or replaced. It was brand new except the drive housing and gear sets.

Then one day just as it had started to run hot it quit. Never found what the cause was.

Must have been spook's I guess.
Now that's one for the books.
 
"Motors: You can't live w

"Motors: You can't live with them (at times), and you sure as hell can't live without them!

I assume you 'burpted' the cooling system of air, made sure no rust or other crud was collecting in the heat exchanger, had a good circulating pump (with all it's blades intact), etc. Of course you did! And the fool thing still zapped you all summer.

Motors: You can't live with them (at times), and you sure as hell can't live without them!

Jeff"
 
"Folks, I sure appreciate all

"Folks, I sure appreciate all the ideas, But up to now I dont think I missed anything. I do still need to remove the heat exchangers and clean, clear, etc
Anyone thinking I am missing something please pipe in

Thanks again"
 
Things to check.
Timing / dis


Things to check.
Timing / distributor advancing more than it should. I doubt this but check for vacuum leaks. All cooling lines are connected at the correct location.
It's easy to cross the lines.
Outdrive water intake to impeller for blockage. Leaking water supply line at the bellows area of the gimble ring.(line from drive to transom mount) Connection for the water feed tube from the pump at the top of the drive could be leaking(bad seal / mis-aligned)

Lower part of water jacket / block full of dirt / sand etc.
If this is a closed cooling system with antifreeze in the engine a blockage of the water jacket should not be a concern.

Just a few things that come to mind. Good luck.
 
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