I have a 1999 Volvo Penta 5.0 GL/SX with ~900 hrs on it. Recently it has had some heat soak/overheat issues. At idle on muffs it will sometimes creep to ~200 deg then as if thermostat opens drop back down to ~160. Idling in the water seems to run slightly lower. At speed temp is temp is OK, even under high loads. If I run it under high loads then quickly go to idle it will heat soak and climb to ~200 deg, if I put boat in neutral and increase RPMs to say 1200 RPM the temp immediately starts to drops down. Also rises seem to run slightly warm, can almost not keep hand on them after running, they are about 3 yrs old (salt water) but had one off recently and didn't look to terrible, and if they had compromised water flow they would run warmer.
So far I have replaced: impeller, thermostat, thermostat housing, removed and checked clean out under shift linkage cover.
I read Dons linked VP overheat diagnose manual (thanks BTW) and thought I had it figured out. When I slightly pressurized the raw water intake with drive intake taped shut there was a water leak where water inlet goes thru transom plate. I was due to pull drive for annual inspection and I never did U-joint bellows so it was due . So I pulled drive hoping o-ring would be compromised...it was not. Then I plugged the water tube by the large plastic nut with drive off and still leaked out backside where I couldn't see. The plastic water tube is stuck in the transom shield and it was dark/late so I quit for the night. I was reading my manual there is talk of a drain hole for water draining (winterazation) so now I wonder if the the leakage I see is normal/acceptable. Is there a hole in that tube? Seems like it would always make an air leak and compromise the raw water intake.
So far I have replaced: impeller, thermostat, thermostat housing, removed and checked clean out under shift linkage cover.
I read Dons linked VP overheat diagnose manual (thanks BTW) and thought I had it figured out. When I slightly pressurized the raw water intake with drive intake taped shut there was a water leak where water inlet goes thru transom plate. I was due to pull drive for annual inspection and I never did U-joint bellows so it was due . So I pulled drive hoping o-ring would be compromised...it was not. Then I plugged the water tube by the large plastic nut with drive off and still leaked out backside where I couldn't see. The plastic water tube is stuck in the transom shield and it was dark/late so I quit for the night. I was reading my manual there is talk of a drain hole for water draining (winterazation) so now I wonder if the the leakage I see is normal/acceptable. Is there a hole in that tube? Seems like it would always make an air leak and compromise the raw water intake.
