Volvo penta AQ125b overheats when on plane

[wbodzon]

Volvo Penta AQ 125B, with a 270 sterndrive, overheating when on plane. I have checked almost everything. Seawater pump, freshwater pump. Replaced the exhaust(venturi) manifold.. Thermostat, heat exchanger all seem good. Cylinders all have good compression. Boat overheats when up on plane. When it is in neutral, outdrive is fully submerged it is fine. Any ideas on possible seawater suction problems through the outdrive? Doesn't seem any of the intake ports are clogged either?
Thanks,
Walter

 

[Don S]

Re: Volvo penta AQ125b overheats when on plane

There is a water hose between the transom shield and the outdrive. Where it attaches to the outdrive, the end of that hose connections corrodes away allowing it to suck air.

 

[Robj]

Re: Volvo penta AQ125b overheats when on plane

Don is right, he is most of the time. You probably have to replaqce the part that attaches the raw water hose to the outdrive. It is most likely corroded and sucking air.

Good luck

Rob.

 

[JAL51974]

Re: Volvo penta AQ125b overheats when on plane

There have been several other threads on this recently on overheating 125A engines, check out the suggestions there to give you a full picture of the possible problem areas in this raw water cooled system. Be patient as you check everything out!

Joe

 

[Maclin]

Re: Volvo penta AQ125b overheats when on plane

The fitting mentioned is underwater at idle and below planing speeds so even if the fitting is leaking or the hose is bad it will still draw in water ok. Once it comes up on plane the fitting and hose are out of the water and suction will break if either is bad. And that fitting definitely corrodes away, it is a wear item that needs to be replaced, usually when the drive bellows is serviced, so check it out.

 

[wbodzon]

Re: Volvo penta AQ125b overheats when on plane

Thanks guys,
I'll replace the fitting and let you know.
Thanks again,
Walter

 

[elkslayr]

Re: Volvo penta AQ125b overheats when on plane

I have an aq120b and expirensing the same problems ,but when on the muffs or when the drive is sitting in the water at idle it will run between 180-240 dont think thats the normal operating temp at ldle .Also would like know where the suggestions are to find the picture for this fitting is .I suspect it to be the hose from the raw water pump the the drive or the part that seporates the inside of drive to the outside thanks if you can help