AQ125 B cooling

[bblst]

Hello, I have a 1986 Bayliner with an AQ125B/270 outdrive. I am having an issue with the boat overheating. When idling and trolling about the I can remove the freshwater strainer cover and water will cascade out of the exchanger. When I get going at higher speeds I lose the cooling water and the boat overheats, (coolant is released from the radiator cap). I can let it cool down and water will flow when idling. I replaced the cross piece and impeller but get the same results. Am I missing something? Any help would be greatly appreciated. Thanks.

James

 

[PiratePast40]

Re: AQ125 B cooling

A common occurance with these drives is the water neck fitting eroding from the inside. That fitting is located just below the driveshaft bellows and erosion and wear isn't allways visable from the outside. While at idle speed, the fitting is under water so everything is fine. Once on plane, the fitting is out of the water and can suck in air. Actually, any suction side leak will prevent the pump from drawing water but that's the most common and the one to check first. You should pull the hose off to really be able to tell the condition of the fitting and it's special beaded o-ring.

 

[dennis461]

Re: AQ125 B cooling

Is the exhaust manifold flowing water OK?
One hard to find problem is the raw water pump case can wera out.
The rubber impeller wears the most, but a very old pump casing may be worn enough to not provided goo enough suction when up on plane.

Test you plumbing first though for leaks.