overheating issues

Hi Guys,

I've had this trouble the last two times out:

Launch the boat and head out of the harbor and everything seems fine. Once I get up to cruising speed, the water temperature quickly rises to the point where the alarm sounds and I shut down the engine. I then hook up the fresh water hose to the inline Perko Flush Pro attachment on the input side of the raw water pump and start the engine. Temperature quickly drops back to normal. I shut down the engine, disconnect the fresh water hose and start the engine. Boat stays cool the rest of the day.

I've just replaced the raw water impeller about 20 hours ago. Each time I return from a trip I flush the engine with a garden hose using the Perko Flush Pro.

Any ideas what is happening?

I'm thinking either the Perko Flush Pro has got a valve that is sticking or that my thermostats are going bad.

I'm also wondering how the raw water impeller gets primed since it sits above the water line. Is there a lift pump in the stern drive? or is it just pressure from the boat motion?

Thanks in advance,
Terry

Might be the seal in the pump needs to be replaces. The pump is self priming and if the seal is bad or there is a grove worn in the shaft where the seal rides, the pump will suck air in through the seal instead of water through the outdrive. I fought that problem for years until I finally replaced the seal.

A temporary fix(I went this rout for years) is to pre-fill the filter basket with water before each day. If you don't do something you will burn up the impeller running it dry.

Mike

p.s. Was this a problem before you replaced the impeller? With the engine running, do you see water dripping from the pump, pipe connections or basket lid? All drips are a source for air to enter when the pump tries to prime.

part number 827247, two seals per pump if i remember correctly

Thanks Mike, I bet that's it. I do see some water dripping from the raw water pump when I flush the motor. Must be just enough of a leak to prevent priming. Are the seals hard to replace? I remember there not being much access when I changed the impeller.

Fairly easy job. You'll need to remove the pump from the engine to do get to the seals. Start off by removing the water hoses and basket strainer. When you remove the pump from the engine, keep an eye out for part #2 in the second picture. On my pump(AQAD40 has a larger pump) that part is rubber and often stays in the engine hole instead of coming out with the pump. No big deal, just be aware the part is there and you need to locate it.

With the pump off, remove the impeller, flip the pump over and remove the snap ring(part #13 in picture one). The shaft and bearings should slide out the back end of the pump. I don't remember if the seals come with it or stay in the pump. You might want part #11, it's a o-ring volvo number 960166

http://www.bocapix.com/data/512/41pump.jpg

http://www.bocapix.com/data/512/41pumpbasket.jpg