Aq151c overheating

[T1ony]

Hi, I wonder if some one can help?one of my engines AQ151c is overheating, I thought head gasket but no I put a tester on several times and it is ok,changed the thermostat, serviced the raw water pump, took the heat exchanger off and took apart and cleaned, checked the timing and it is about10-15 past TDC and should be 6 BTDC will this make it overheat? there is no adjustment on the distributor so will have to take out and reset. she would be fine at 6-10knots but at 17-27knots within 3mins overheated but now she gets hot at low speed and cuts out.

 

[Don S]

Re: Aq151c overheating

Depending on which drive you have, it may be the hose connection for the water pickup hose where it hooks to the drive. They have a tendency to corrode away and cause the drive to suck air instead of water. At low speed it would be under water, but at higher speeds would be out of the water and suck air. Don't just look at it, pull on the hose, they usually break off in your hand if corroded enough.

 

[T1ony]

Re: Aq151c overheating

Hi Don, thanks for the info, I'll be taking her out of the water soon and I was going to replace all hoses to the drives as the previous owner only did things when they went wrong as I found out to late,spent three years putting her right, the out drives are 290 sp modle SPA I think looking at pictures, so the timing has nothing to do with the overheating.
thanks again T1ony

 

[djs-jds]

Re: Aq151c overheating

Hi, I had the same problems on both of my AQ151C's on my last boat. I Replaced all the hoses etc and they were fine at tick over but over-heated under load. The problem was caused by the oil cooler. Hidden behind the exhaust manifold is the small oil cooler. It can be removed without removing the manifold by removing the lower pipe and sliding the inner sleve downwards. The inner sleeve has about 80 tiny tubes which get blocked. Use a thin cut coat hanger to poke out every hole. Problem solved. Not even Volvo mechanics knew about this and it took nearly a year of trying everything else.

 

[T1ony]

Re: Aq151c overheating

Thanks DJS I will look for this second oil cooler, my manual does not show it, can you tell me will there be oil spilt when taking out,
regards T1ony