4.3 liter overheating

[Cheesburger]

1988 Searay Seville 21CC 4.3liter.

I was given this boat, by a friend. It had been sitting for about 4 years. I was told the engine had been rebuilt twice already. I have changed the impeller in the outdrive and the waterpump that is bolted to the front of the block. I have also changed the thermostat. It ran fine while on the muffs. Temp came up and then went down and stays in range. After several test on the muffs, I put it in the water for a test run. It quickly ran up to about 190-200 and would not come down. I was reading a post that said to check the intake gaskets...I did and that was not the problem. I am very close to just replacing the engine altogether.

Help

 

[Bt Doctur]

Re: 4.3 liter overheating

Were the manifolds and riser very hot too?
might be a bad sender or clogged manifolds/risers if motor was left dry and this is a recent startup .Some loose scale may have clogged things up.

 

[Cheesburger]

Re: 4.3 liter overheating

Yes they seamed overly hot. But why would it over in the water but not on the muffs?

 

[UpperUpsilon]

Re: 4.3 liter overheating

Generally, on the muffs you run the engine alot slower, and not in gear (no load). Enough water is there to cool the engine at low heat-production, but once that heat vamps up, there is not nearly enough coolant going through the block and manifolds.

 

[Cheesburger]

Re: 4.3 liter overheating

Thanks a bunch. I will pull them off this weekend and update what I find.

Thanks again.

 

[Cheesburger]

Re: 4.3 liter overheating

Okay,
I pulled the risers. Yes there was some scaling and blockage(35% - 40%). Strange that the gaskets block 2 of the 4 ports on their own. I am cleaning and putting back together this weekend. Fingers crossed...

 

[Zackman]

Re: 4.3 liter overheating

Make sure you have the right riser gaskets. There's different gaskets for different types of cooling arrangements. The wrong gasket may have been part of your problem.​

Here is a link to the Mercrusier Service Bulletin 99-10, which explains all this in detail.​

http://www.boatfix.com/merc/Bullet/99/99_10.pdf​

Also, if they are as bad as you make them sound (35% - 40% blockage) I would think you would want to replace them and maybe the exhaust manifolds too???​

 

[Cheesburger]

Re: 4.3 liter overheating

Good information to have. Glad I read this before buying the gaskets.
Thanks for the heads up

 

[Cheesburger]

Re: 4.3 liter overheating

NO MORE OVERHEATING...I cleaned the risers and manifolds, replaced the reiser gaskets with the new 4 hole gaskets (thanks for the info). Running cool!!!