Engine overheating

[Lou C]

part #10 can crack and the irregular o ring part #8 that fits into the pivot housing can slip out of place when installing the drive, either can cause an air leak. Same design as the OMC Cobra. When I install the drive I use some OMC triple guard grease to hold #8 in place. If you disconnect your raw water hose at the impeller, tilt the drive up and fill the hose with water, see if you see any leaking where this part #10 is or the joint between the drive and the pivot housing (o ring #8). Believe it or not I have the same plastic fitting on mine that was on it when I bought the boat 18 years ago, they can crack if water is still in the drive and its not tilted down in cold weather. The Cobra has a drain plug just outside of where that is, not sure about the Volvo. The plastic part actually has a small hole in it to allow it to drain out of that drain plug (#9 in that diagram).

 

[ConchPirate]

Thanks guys! So if it is either the plastic fitting (circled in blue) or the plumbing in the outdrive, I'm thinking that while the boat is on the lift, I can disconnect that hose where it connects to the plastic piece on the gimbal, connect it to a suitable piece of hose with union fitting and allow it to be submerged in the water. Lower the outdrive again without pinching the hose, and then if it is an air leak at that plastic fitting/gasket or in the outdrive, I would know because it would get sufficient water without the air or exhaust gasses and not overheat at idle the way it does now. Should that work??

Also, if my test would work, do any of you know what size that hose ID is there at that union? Is it the same size as the hose going into the pump?

 

[ConchPirate]

One follow-on question - where does the plastic pipe usually crack? On the side where the hose connects, or is it usually on the gasketed side?

 

[Vparzial]

I had a similar issue and it was my water pump seal was really worn out and not holding a good seal around the spindle that connects to the impeller. Once I changed the seal on the outside of the pump my issue went away. I would double check and make sure that there is a good seal there even if it is new. (See Image). Also check and see if the pump housing easily comes off of the spindle. If it does then it is most likely wobbling on it and breaking your seal.

If you put your hand on the thermostat housing how hot does it get with the hose hooked up to it? On the hose it should be cool to the touch when running even after the motor has been running for a bit.

 

[ConchPirate]

I had a similar issue and it was my water pump seal was really worn out and not holding a good seal around the spindle that connects to the impeller. Once I changed the seal on the outside of the pump my issue went away. I would double check and make sure that there is a good seal there even if it is new. (See Image). Also check and see if the pump housing easily comes off of the spindle. If it does then it is most likely wobbling on it and breaking your seal.

If you put your hand on the thermostat housing how hot does it get with the hose hooked up to it? On the hose it should be cool to the touch when running even after the motor has been running for a bit.

Pretty sure the pump is good. If on hose through flush line it runs cool, and I can hold my hand on the thermostat housing, manifolds and risers easily for any length of time. Same if I connect the pump supply to the other engines feed line. Temps never go above factory recommendations anywhere as per IR gun checks for up to 30 minutes. It only overheats when connected to the outdrive water supply and the manifolds get over 150 in a few minutes. But I will keep your issue in mind after checking the input line for leaks.