Penta AQ131A / overheating and high oil pressure?

[bass7man]

Hi, I have a Penta AQ131A inboard on my bayliner. At an idol everything is fine. If I kick it up the oil pressure goes way up...It will top out at full throttle. Also it will overheat if i am half throttle or more for more than 20 seconds...It blows out the top of the cap...I have replaced the cap thinking that was the only problem before realizing the oil pressure problem. I did buy a thermostat but I am having second thought about that being the problem. I think it may be a head gasket but not sure and am looking for someones opinion. Any ideas?

 

[Bondo]

Re: Penta AQ131A / overheating and high oil pressure?

Ayuh,.... Have you changed the raw water impeller,..?? That's Always the 1st place to start with an overheat situation,...

I'm guessin' yer oil pressure problem is the gauge, not the motor,...
Tee in a mechanical gauge to cross-check yer present gauge,...

Drainin', 'n pressure testin' the coolin's system's motor side should tell ya whether ya got a bad head gasket, or bad heat exchanger,...

 

[bass7man]

Re: Penta AQ131A / overheating and high oil pressure?

Impeller was checked first. It was good. Thanks for the other advise!

 

[captmello]

Re: Penta AQ131A / overheating and high oil pressure?

So, at Idle, it doesn't overheat?

 

[bass7man]

Re: Penta AQ131A / overheating and high oil pressure?

Not only does it not overheat at an idle.... If you run it until it starts to overheat and come through the radiator cap, then drop it down to an idle, it will stop overheating and after about 30 seconds you can do it all over again...run it until it starts coming through cap...drop it to idle for 30 or so seconds...maybe a little longer but no much.

 

[bass7man]

Re: Penta AQ131A / overheating and high oil pressure?

Also...if you are at idle the oil pressure is at normal pressure...at high speed it tops out...then at idle again it is at normal pressure.

 

[captmello]

Re: Penta AQ131A / overheating and high oil pressure?

One common overheating cause is the water intake fitting right below the ujoint bellows corrodes and causes air to leak when the boat is on plane. At Idle the fitting is submerged and cant suck air. Pull the hose off the fitting and have a look.