Please help! 170aq volvo penta 250 outdrive

[Steel84]

I have a 1971 volvo penta 170aq that i think might have an overheating issue. I took the boat out yesterday for a morning fishing trip and everything ran nice and cool. I was going to go for an afternoon trip as well so Idecided to take the boat out and fill up before I went out again. Within a few minutes I noticed that it was overheating. I inspected the engine and noticed that none of the cooling lines had water in them. I let the engine cool off for some time and also inspected the impeller which was fine. I started the engine again and this time water was running through the lines again and cooled the engine just fine. Could I have had some kind of vapor lock? I also noticed that the two elbow pipes that run next to each other on top of the engine were kind of warm and the temp guage would fluctuate between cold and warm but not like it was before. Is there something like a bad thermostat that could cause this? The engine is freshwater cooled only and ran nice and cold before. Any kind of advice would be greatly appreciated. Thank you
Pat
1971 Thompson 20' Fisherman

 

[PiratePast40]

Re: Please help! 170aq volvo penta 250 outdrive

http://www.volvopentastore.com/Intermediate-Housing-Aq-Drive-Unit-250/dm/*******.598871691--**********.391681087--store_id.366--view_id.317187

In the link above you'll see a fitting that connects the rubber hose to the outdrive for raw water supply to the engine. It's part number 28 in the drawing. It's common for that fitting to corrode and allow a suction leak when on plane since it'll be above the water at that point.

You may need to take the hose off to get a good look at the fitting. They tend to corrode internally and you may not see the damage with the hose still connected.

That's the most common bad actor but check all along the water suction path for leaks that will impede the pumps ability to draw water.

 

[zbnutcase]

Re: Please help! 170aq volvo penta 250 outdrive

Yes that fitting is a common Volvo problem, check that first. You said impeller was good, but I have seen worn housings cause the same problem.