overheat at WOT

[mellowjs95]

me and my bro where on the water today he has a 1985 bayliner with aq125 volvo/penta when we hit wot engine overheated. we took it home checked the sea water pump and it was fine. we took out thermostat put it in hot water and it opened properly. look in book and it said check timing which was fine. we put thermostat back in and started engine with muffs on ran great and temp was good 160 i believe. now if u take the cap of while engine is running should water be flowing thru the engine in the closed system?

 

[maxh]

Re: overheat at WOT

check the fitting on the outdrive, it may be sucking air...

 

[jerryjerry05]

Re: overheat at WOT

Check the fitting on the drive then look at the exhaust manifold.Pull the boot and see how corroded the end of the manifold is.
There are three things that can be going wrong.Manifold:corroded,restricting flow.Heat exchanger: clogged restricting the flow.Water pump:seal going bad and sucking air or the excentric cam wore and the pump not delivering enough water.If it says Volvo on the manifold then the chances are it's pretty old and rotten.They can look NEW but be bad.J
Fill out the profile,that way we know if it's run in salt or fresh water.J

 

[mellowjs95]

Re: overheat at WOT

Check the fitting on the drive then look at the exhaust manifold.Pull the boot and see how corroded the end of the manifold is.
There are three things that can be going wrong.Manifold:corroded,restricting flow.Heat exchanger: clogged restricting the flow.Water pump:seal going bad and sucking air or the excentric cam wore and the pump not delivering enough water.If it says Volvo on the manifold then the chances are it's pretty old and rotten.They can look NEW but be bad.J
Fill out the profile,that way we know if it's run in salt or fresh water.J

sorry bout that he only runs it in fresh water and we looked for the fitting and i couldnt find it.

 

[cr2k]

Re: overheat at WOT

Lift the drive, look up and find what looks like a heater hose. Follow it back to the outdrive part, it connects with a housing that looks like a small thermostat housing. This is where the water is sucked through the outdrive pivot bushing.
The rubber gasket/o-ring that goes under this may be damaged and you will suck air here. If the bushings are going (the outdive seem loose in its bushings) you can suck air via the worn bushing.
Check the other end where it goes through the boat also.

Fix for that is to install a scupper and a seacock in bottom of boat and bypass complete disassembly of the drive to replace bushings.

 

[mellowjs95]

Re: overheat at WOT

Lift the drive, look up and find what looks like a heater hose. Follow it back to the outdrive part, it connects with a housing that looks like a small thermostat housing. This is where the water is sucked through the outdrive pivot bushing.
The rubber gasket/o-ring that goes under this may be damaged and you will suck air here. If the bushings are going (the outdive seem loose in its bushings) you can suck air via the worn bushing.
Check the other end where it goes through the boat also.

Fix for that is to install a scupper and a seacock in bottom of boat and bypass complete disassembly of the drive to replace bushings.

we are going to check it in the morning. my other question is since it has a closed system if u take the cap off should u see the anti-freeze flowing like u would in a car radiator with the thermostat out?

 

[Fun Times]

Re: overheat at WOT

sorry bout that he only runs it in fresh water and we looked for the fitting and i couldnt find it.

This might help, Keep in mind, There is a classic problem with the older Volvo drives. Of course check and replace the impeller, but unless you find missing blades or permanently bent blades that might not be the problem.

The Volvo has the water pump on the engine and sucks the water up from the outdrive. There is a hose that goes from the transom plate to the drive. Your problem is might be the fitting on the drive that the hose connects to. What happens is either the fitting corrodes or the seal goes bad and leaks. When the boat is idling this fitting is below the water so it still sucks in water. When the boat gets up on plane this fitting is now out of the water and now sucks enough air so you don't get water to the engine and you overheat. Drop back off plane and you get water again and the engine cools down.



Take a look at the linked diagram. The fitting is item #1 and the seal item #2.

Good luck with it.http://bpi.ebasicpower.com/mm5/apps...E=93&INAME=OMCVOLDiagrams/images/GLMOMC06-160

 

[jerryjerry05]

Re: overheat at WOT

You have 2 caps on this outfit,1 is for the closed system and the 2nd is for the raw water system.The cap on the closed system when removed you might see antifreeze moving.The circulating pump rarley NEVER goes bad.
When you remove the other cap raw water should come out.The raw water goes thru the strainer into a heat exchanger.If you run in salt or muddy water or suck up a lot of sand this will clog.Muratic acid can be used to clean it out.Be carefull as it will eat the brass if left too long.Try back flushing it first.
But the culprit is probably the manifold. That's where I'd look first.J