Volvo overheating after 40 minutes

[shute421]

I ran my boat for 40-45 minutes last night tubing/skiing and what not......boat ran good for all that time...40 minutes into it I noticed the temp needle going up, I immediately headed for my dock, temp gauge was still going up.....saw some steam/smoke coming from the engine compartment...almost at the dock and then I shut it off....lifted up the engine compartment and a whole bunch of steam/smoke came out.....let it cool for a while before I looked at it and noticied antifreeze all over which I had to pump out. There weren't any hoses busted, and I think the antifreeze came out from the cap. The engine is a Volvo AQ171A that has 2 cooling sysytems....one which uses fresh water and the other that uses 50/50 water and antifreeze......any feedback on first instinct on what it might be....impeller, thermostat...water pump....???????

 

[lilmandavis]

Re: Volvo overheating after 40 minutes

id probably hook it to the muffs to see if water IS circulating. when was the impeller last changed? what about the thermostat? thats easily checked in some hot water. make sure and dont let the thermostat sit on the bottom of the pan, have a thermometer so you know what temp it opens at in the pan to. usually the circ pump dont go out unless thier really bad.

 

[Don S]

Re: Volvo overheating after 40 minutes

Here's a little hint the next time you get an overheat like that. Instead of continuing to run the engine, shut it off and let it sit for a minute or two.
Your problem may have been that you picked up a plastic bag (or something) over the water intake holes on the drive. When this happens, you get an overheat, but the suction from the raw water pump holds the bag in place. If you shut the engine off, the suction stops and the bag falls off do to the rocking of the boat. Then when you restart the engine runs cool again.
With no raw water to cool the heat exchanger, it will get hot and cause the antifreeze to boil out..
Not a good idea to keep going with a hot engine unless it's an emergency and you have to keep the engine running.

 

[shute421]

Re: Volvo overheating after 40 minutes

update....I changed the impeller yesterday and it was in definite need of replacing, the thing was pretty much totaled......thanks to Don S, the dishwashing liquid worked great....thanks Don......unfortunately that didnt fix the overheating....after I installed the new impeller, I started the boat and let it idle for 5-10 minutes or so and watched the temp needle slowly go higher...instead of 40 minutes and then overheating, it was heading towards overheating after 5 or 6 minutes of idling....shut it off when it was getting hotter than normal....which was when the needle was 3/4. I haven't changed the thermostat, but would this be my next step?? Water pump?? Not sure if the water is flowing.....any ideas????

 

[Don S]

Re: Volvo overheating after 40 minutes

When it's running, do you have a good flow of water coming out of the transom shield? If not, you have a restriction in the cooling system somewhere, or an air leak in the suction side of the raw water cooling system.
The air leak could be the hose connection on the outdrive itself. If the end corroded off (Common problem) your pump will suck air when on plane or on muffs. IF it's sitting in the water, it may cool because that connection and hose would be under water, on plane it's above the water.
It may also be your thermostat. But they don't go bad that often.