clogged water passages in power head

[slowstick]

My motor is evinrude, 4 hp, 1976 year. It runs so hot it shuts down by itself. I put in new wear plate, impeller, but still runs hot. I put lower unit in bucket of water on a drill press table. I put the drive shaft in the chuck, and at the slowest speed of the drill press, the water shot up about a foot and was the diameter of the rubber bushing. So I am getting a lot of water to that point.<br /><br />I attached a flexible hose to the pipe that carries the water to the power head and blew on it. It is not blocked, but I had to blow pretty hard to get the air thru.<br /><br />What can I introduce into the narrowed power head passages (via the long pipe) that will eat away at the build up on the water passages in the power head, that will not eat thru the aluminum and into the cylinders? thanks

 

[KC49111]

Re: clogged water passages in power head

I recently went through the same with a 1970 4 hp. There are a few threads here that give good advice from people such as Chinewalker and Paul Moir. If your engine is anything like mine, I'm not sure you'll find a product such as Salt Away or Salt X will do the job as I found the salt deposits very solid (I didn't try them). There are also 2 cooling paths, so you might clear one but not the other. The usual advice is remove the cylinder head and the exhaust cover plate on the side of the block and use various picks and brushes to clear the passages by hand, then surface the head with wet and dry sand paper on a flat surface and reinstall with new gaskets. The head gasket is probably due for renewal anyway if the engine has been running hot and you can decarbon the pistons with Engine Tuner while you have it apart.

 

[slowstick]

Re: clogged water passages in power head

Thanks, but today I removed the head with the intention of taking it all apart like your post says. I took off the long copper tube that conducts the water from the pump to the head. And right there at the top of the tube was the obstruction. It was not hard, beige colored, and came right out when I slapped the tube on the edge of the workbench. I reconnected the long tube and blew on it and the air went right on thru easily. I also found where the water exit hole was too when the water sprinkled out of it too.<br /><br />Boy am I lucky.