Volvo Penta AQ131-A overheating

[Zeker]

I have a project boat-a 1986 Bayliner powered by a Volvo AQ131-A. This motor has a heat exchanger and a raw water cooling system. I have an occasional chirp from the front of the motor that appears to come from the impeller casing or timing belt cover. The brass impeller casing gets very hot which doesn't make sense since it should be pulling raw water. I disconnected the hose coming from the outdrive and backflushed the lower part of the system and it flowed easily. I changed the impeller paying particular attention to the keyway and it was quiet for about 3 minutes and then the chirp returned. The impeller casing again got very hot. I have a hunch that the new impeller probably couldn't stand the heat and is again cooked. The motor runs at 210-225 degrees and I am running it in a tub. Is there a bearing or bushing in the timing cover that would heat the impeller casing if it failed? If so, how difficult is it to pull the cover and replace the bad bearing? Is there another answer to my problem? I appreciate whatever info you can give me.

 

[Bondo]

Re: Volvo Penta AQ131-A overheating

and I am running it in a tub.

Ayuh,... There's your Problem....

Impeller pumps will Not Suck, they have to be fed water 1st...

 

[Zeker]

Re: Volvo Penta AQ131-A overheating

Should I pour water in the raw water strainer housing before starting to prime the impeller and creat vacuum?

 

[robjen1019]

Re: Volvo Penta AQ131-A overheating

I always tested my engine in a tub. I just removed the prop and put drive in a tube and added hose and water. Always seemed to prime itself rather quickly.
Make sure that there are not any leaks in the water system. Any air leaks will cause trouble with the cooling system. One of the known problems on these drives in the nipple coming off the outdrive. It gets corroded very easily. Also You might try changing the thermostat if you haven't yet.

 

[Zeker]

Re: Volvo Penta AQ131-A overheating

I thought the thermostat was part of the coolant system and not the raw water system. Am I mistaken? Do you have any idea where I could find an owner's manual and would it be helpful?

 

[Don S]

Re: Volvo Penta AQ131-A overheating

The raw water side of the cooling systems is 1/2 of the system, it's what cools the antifreeze side of the cooling system.
In boats, the engines radiator can't be cooled by air, because there isn't enough air flowing past the engine to cool a radiator, thus the heatexchanger, which basically does the same thing as a radiator, but the air is replaced by water from the lake, stream, or ocean.
Now, on your 131, the raw water pump had better suck water up from the outdrive, otherwise you will overheat.
If you go uip to the adults only stick, you can download an engine manual for your 131 that has a really nice diagram of the cooling system. I think after you look at it and undersand it, you will see how things you wouldn't expect can cause an overheat.
The only reason your pump housing will get hot is when the impeller is burning up from spinning with no water. Air leaks cause that. One of the most common is the water hose connection on the outdrive. They corrode away and allow air to enter the cooling system instead of water. Especially on muffs or when on plane.

 

[Zeker]

Re: Volvo Penta AQ131-A overheating

Thanks for your help. Today I plan to add second hose clamps on both ends of the rubber hose and remove and test the thermostat. I downloaded that doc on the file sharing site and it is a great help. I notice that my 275 outdrive isn't listed. Is the 270T manual the one I should use?

 

[captmello]

Re: Volvo Penta AQ131-A overheating

Pull off the "S" hose that goes from the top of the intermediate section of the outdrive to the transom plate and examine the fitting on the outdrive, what Don reffered to as the "hose connection" for corrosion.

Use the 280 manual. it is much better than the 270 manual. the only difference between the 275 and 280 is the lower gear housing.