volvo aq125 overheating problem

[Tamster0420]

i have a 1985 bayliner capri with a volvo aq125 4cyl engine.
when i take the boat out on the water and run it. it over heat. the faster i go the faster it over heats. i have check the raw water pump and the impeller an its fine. i have hooked up a clear tube to see if im getting enough water going in the engine but i dont really see that much. when im going around 300rpm my heat exchanger filter water comes out of it and its really tight on there. am i getting and air leak and is it my exhuast manifold?

please help!!

thanks

 

[Ride The Lightning]

Re: volvo aq125 overheating problem

Hi,

could be more than one causes:
- thermostat
- closed cooling circuit (rust etc)
- heat exchanger is scaled
- cooling water feed line in the drive is sharped or something like that

Regards
Lars

 

[Don S]

Re: volvo aq125 overheating problem

A plugged up exhaust manifold will diffinitly cause it to overheat that way, along with the heat exchanger Lars mentioned.

 

[Robj]

Re: volvo aq125 overheating problem

Also the intake fitting on the drive tend to get corroded allowing it to suck in air. The engine would be OK until you get it on plane when that part of the drive is out of the water and it starts sucking in air.

Have a great day,

Rob.

 

[JAL51974]

Re: volvo aq125 overheating problem

Heres the way I located the air leak on the drive unit side:
disconnect the line leading from the outdrive to the heat exchanger and put a vacuum source on it (rigged up a shopvac to it); covered the water tube junctions on the drive with shaving cream then started the vacuum. You can easily see and hear the areas that are sucking air then...those are the areas you need to repair/replace, etc. A likely culprit is that water connection fitting and the gaskets surrounding it...many get so eaten up on the inside of the connection yet look good on the outside causing poor seal and air intrusion when on plane, etc.
Good luck.

Joe

 

[Maclin]

Re: volvo aq125 overheating problem

I think like Robj, the hose connection fitting on the intermediate drive corrodes easily and will let air in and the raw water pump loses suction when it is on plane. You would probably have this problem on the muffs as well. When it is in a lake the hose fitting is under water and the problem vanishes, kind of sneaky that way.