1992 Volvo Penta 431B-DP Intermittent Overheating

[tekati]

1992 Chaparral 28' with 431B and DP stern drive.

Rebuilt engine with all new water pumps, manifolds/risers, thermostat and a non professionally rebuilt carburetor and what I mean by non professional is it was just done by a normal mechanic and not tested on a test motor etc but rebuild kit was used.

Overheats randomly at both high throttle operation and when idling in gear for extended periods.

This is the motor with the power steering pump.

A little history. We put in a Jasper rebuilt motor after the original got hot and put a hole in the piston.

The out drives were rebuilt about 3 years ago.

The boat is raw water cooled and is in salt water.

Ideas???

 

[Don S]

Re: 1992 Volvo Penta 431B-DP Intermittent Overheating

What's the condition of the raw water pump and impeller?

 

[tekati]

Re: 1992 Volvo Penta 431B-DP Intermittent Overheating

All the water pumps are new.

 

[muscmkr]

Re: 1992 Volvo Penta 431B-DP Intermittent Overheating

I just posted to another boater having a similar problem. Definitely could be risers and manifolds need replacing but if you are confident this is all good and your impeller and circulating pump are good then here is what happened to a boat I had at one time. similar thing... intermittent overheating. No real reason, fast, slow, one hour or ten hours of boating. The engine ran great, no water in the oil, no fouled plugs, compression check was good. When I traded the boat in they found a cracked head. Hard to believe but true. Hope you find a simple solutions but definitely don't let someone, even a mechanic, tell you it can't be a cracked head. good luck

 

[tkrfxr]

Re: 1992 Volvo Penta 431B-DP Intermittent Overheating

Look at the water flow....

Check the inflow hoses and connections.

Make sure air is not being sucked into the system somewhere....

Check the outflow hoses...

Check the flow out through the manifolds and risers....

The water pump and impeller are smack in the middle of the system...check them first...make sure the o-ring in the pump housing is good, and seated properly...

there is an overheat troubleshooting guide on this site somewhere....

Try:
http://www.4shared.com/file/50572185/e88f1d89/Volvo_Penta_Overheat_Diagnosis.html