Running temperature on a Volvo Penta 5.0L GL

[2003stardeck]

i have a 2003 volvo penta 5.0L GL that was overheating. i replaced the thermostat and experienced no overheating however when i slow the boat down and idle around, i notice that the temp gauge rises 20-40 degrees. As soon as i get back on the throttle the temp gauge drops back to the normal operating temp. Can anyone tell me if this is normal and what the temp range should be on this engine. it seems like to me it is not moving enough water at low speed. Thanks.

one other note. before i bought the boat it was run onto a sandbar and trashed the impeller. They did install a new impeller but when i decided to replace the thermostat i found 9 pieces of the old impeller in the thermostat housing. where else should i be looking for pieces of the old impeller?

 

[gbeltran]

Re: Running temperature on a Volvo Penta 5.0L GL

No it isn't normal. Mine stays at 170 or so once it's warmed up. Idle or full speed. When was the last time the impeller was serviced? Do you boat in salt water? Hours on the engine? Maybe some of the cooling passaged are getting plugged up. Is it open or closed cooling system?

 

[2003stardeck]

Re: Running temperature on a Volvo Penta 5.0L GL

fresh water. low hours. not sure how to tell if it is an open or closed system?

 

[AJK737]

Re: Running temperature on a Volvo Penta 5.0L GL

My understanding is if it's got an impeller it's an open (sea scavenge) system. The impeller draws the water through the outdrive from the lake.

 

[Don S]

Re: Running temperature on a Volvo Penta 5.0L GL

Both types have impellers.
Some engines are cooled completely by water from outside the boat (aka Sea Water cooled). Boats with a closed cooling system have the blocks of the engine cooled by a closed cooling system with a heat exchanger and antifreeze in the closed cooling system. The heat exchanger is similar to a car radiator, but is cooled from sea water from the impeller pump circulating sea water to cool the heat exchanger instead of air.

 

[Lou C]

Re: Running temperature on a Volvo Penta 5.0L GL

Your engine should not heat that much up at idle. They come with a 160 thermostat, they will probably idle at 155-165 and run at 170-175 on plane. When you come off plane sometimes the temp will rise slightly maybe to 180 but not more. If there were pieces of impeller left in the thermo housing, they may not have done a good job on the install. Look also in the line from the impeller to the thermo housing, and in the lines from the thermo housing to the manifolds. Did they replace the wear plate, those get worn (esp if it sucked in sand) and the impeller will not pump well at low speeds. Also any air leaks into the suction side of the impeller (ie in the line from the drive to the impeller) will lower the cooling efficiency. Was sand packed into the water intakes in the drive? If so you may need to back flush the raw water hose. Volvo has a good engine overheat diagnosis article, that tells you how to troubleshoot the whole raw water system and also closed cooling as well.