Volvo Penta AQ170 overheats

[Jeff Wooster]

started overheating so replaced impeller, cleared all copper tubing and oil cooler. bypassed outdrive with hose and bucket and suction was there, but only at around 1500 rpm..(btw at what rpm should i be at normal idle) ..boat stayed at around 190 F....is this the right temp? also, noticed water spewing not only out of exaust but inside outdrive by transom...is this right?

 

[captmello]

Re: Volvo Penta AQ170 overheats

190 is too hot, you should be around 160, no hotter.

Does it overheat on muffs, in the water, only when going fast?slow? There are lots of ways to overheat. Make sure all the intake lines are tight up to the water pump. Pull the nose off at the outdrive water fitting, just below the ujoint (top) bellows. Those fitings are known to rot out and cause the system to suck air.


Normal Idle is about 900RPM.

BTW, welcome to Iboats!!!!

 

[boaterinsd]

Re: Volvo Penta AQ170 overheats

whats is this motor in ? I have the same in my 73 Larson. This place is the best for us, to findout and get help with problems, Welcome to iBoats again.

 

[PiratePast40]

Re: Volvo Penta AQ170 overheats

ANY air leaks on the suction side will reduce the ability to get good flow to the engine. Like the Captain said, that water neck fitting is a common bad actor. It's best to check all the lines to look for cracked, hoses or anything that can allow air to enter on the suction side. You have two water pumps. One is the rubber impeller type raw water pump and the other is the circulation pump. Is the circ pump leaking through the weep hole? If so, there's a good chance the bushings or bearings are shot.

Give us a little better description of the leak by the transom. Is it inside or outside the boat? If outside, sounds like the exhaust boot. If it's the boot, shouldn't have an effect on cooling but should be replaced anyway. Pictures help.

Might want to pull the thermostat and check it in a pan of hot water to see when it opens.

Edit: Just thought of something else. The strainer is on the suction side and can leak as well. The way I checked mine was to add a garden hose fitting just before the strainer. You can then pressurize the suction side, especially the strainer, to look for leaks.

First pic is of the "t" fitting and second is of the strainer leaking. Mine is a 4 cylinder but these should help give you the main idea.

 

[Jeff Wooster]

Re: Volvo Penta AQ170 overheats

so my friend put a new 180 f thermostat in , im guessing this should be less?? also i took off the outdrive and found a hole in the drive bellow, from what i read this should def need replacing but water wasnt leaking from there right?? when i bypassed the outdrive with a hose, the leak would have to be coming from the exhaust bellow right?? im new at this stuff so bare with me ...good info tho so far thx!

 

[captmello]

Re: Volvo Penta AQ170 overheats

Yes, wrong thermo.

With the drive off, check the driveshaft for play. It is the splined shaft that the ujoint yoke goes to. Any play in that and you 'll want to replace those bearings as well.

You may have an Idle relief port on your transom shield allowing water to drain out of the exhaust right next to the exhaust bellows. you just need to watch and see. May be easier to see now with the outdrive off. Run the engine without the outdrive with the water hooked up inside like you did before if you want.

 

[Jeff Wooster]

Re: Volvo Penta AQ170 overheats

ok will check those bearings and already ordered the new thermo kit....i was going to run it but should i cover the drive outlet so it doesnt get water in there ?