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overheating volvo aq170

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I have a 1972 bayliner with volvo aq170 in line six. It runs hot when doing 28 mph. When I shut it off it is very hard to start. There is not much flow out the cooling output. The manuel indicates water runs out through the exhaust and should re direct to the cooling output when it reaches running temp. I never seem to get much flow from the cooling output though.
I was thinking of adding an electronic ignition to make starting easier, but obviously I also need to figure out the overheating.Any suggestions?

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Re: overheating volvo aq170 - Arby Bernt 23:57:35 05/17/03 (0)
I just pulled the twin AQ170 and 280s from an old Skipjack 25. The engines were plagued with overheating. Each water intake had a large plug of material inside of the lower unit. I found the plug when I was rebuilding the water intake on the drive. I can imagine warming up at the dock OK, but when the water is flowing fast, the plug would move up the inlet "galley", and plug the water intake. Overheating would soon follow. One intermediate housing was cooked, and one exaust pipe was cooked.
Check yours(out of the water) for this condition! The mechanic said often the plug in the bottom of the intake would get left in when the hose adapter was used in flushing. This would allow material to accumulate. I have never run the boat, but hope to someday...
Arby
Re: overheating volvo aq170 - Big Dick 19:00:10 11/13/02 (0)
Pig Hunter??

First, change your water pump(s) impeller(s). They are only rubber and you should not even hesitate at changing them every year. Check your sea water intake and strainer(s) for blockage. Then change your thermostat ($12). The thermostat and/or its cavity are not allowing water to flow though. The stat's function is to recirculate water in the block until operating temp is reached then 'bleed' cooler sea water through and regulate the temp. If you are in salt water it eats cast iron and you can get marine growth in there as well. You did not mention if it was 'closed cooling' (sea water on one side of a heat exchanger and engine coolant/glycol on the other) or strait sea water cooling through the entire engine (least desirable as it will eat your block and manifolds/risers in about 5 years). Be inquisitive and take it apart. It is all cheaper than cooking your engine. Don't overheat it or you will deserve the cost of replacing it. Nobody is going to take care of you as good as you can. Good luck

Big Dick

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