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Volvo Penta Cooling--real boat question!

I have a 1992 boat with twin VP 431 DPs. The boat has about 500 hours on it. It has a San Juan Eng. FWC half system and the cabin heater is run on starbord engine. It started running a bit hot on that side. Back-flushed the raw water intake, good. Replaced raw water impeller--was not real bad, no missing pieces anyway, pump looks good. Still same problem, heats under load, cools back down at low RRM. Changed thermostat, no change. Engine pump seems fine, heater works, no weeping. Am thinking a restriction in the "out" side of raw water--manifolds maybe.

Anybody have a suggestion on anything else to check?

Thanks, Dan

D
Oct 1
2005
Thanks for the reply. I did check the raw-water intake side, and it did have new hoses in the out drive this past winter. The 431 is powered by 4.3 V-6.. Dan

"Jim" <Jim@hotmail.com> wrote in message

Daniel
Oct 1
That would be something to check. Had not done so as I only put the FWC on three years ago and do have good water circulation through the cabin heater. Guess I better check that too! Thanks, Dan Daniel
Oct 1
The crap gets stuck in the raw water side. my river jet boat even with a sand trap, will get small pebbles in there at times. Bill
Oct 2
Don't know what twin VP 431 DPs are. We will assume the engines are connected to outdrives.

I had a similar problem once. No one could diagnosis it. Overheated over 1200 rpm. Cooled down at 1100, hot at 1200.

It turned out that the raw water hose connection to the outdrive came disconnected, just a little, it looked like it was a solid connection.

The result was that it sucked air instead of water when the boat started to plane. Off the plane, it returned to sucking water.

D wrote:

Jim
Oct 1
Pull the end cap on the heat exchanger and see if any garbage blocking tubes. Bill
Oct 1
   

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