I had my son give me a hand yesterday afternoon changing out the water-pump and thermostat on my 1999 Johnson Sail-Master 8HP outboard. I had never really done anything to this engine since I bought it new, except change the plugs every couple of years and drain the oil in the lower unit and replace it in the spring. I bought the parts needed for the job at a local marine dealer at a pretty reasonable price and also picked up a tube of marine gasket cement. Luckily, the water-pump came with directions, but the thermostat came in a lot of pieces with no directions at all. I thought that we were going to run into problems, but fortunately everything worked out great. I had downloaded some info on my particular engine from the web,which shows all the parts and provides part numbers. Oddly enough though, the water-pump with the impeller on my engine looked almost new and could probably gone another 9 years, but the thermostat was a different story. The thermostat was working, but I think that it would have failed real soon. It had a lot of salt build-up and grunge in it. If you operate your outboard in salt water and the pump appears to to be working, it would be smart to at least check the thermostat and if it's bad, replace it. The thermostat on my Johnson is located above the cylinders and only had four bolts that hold the cover in place with a little rubber ring gasket. It's under light pressure with small springs and can all pop right out if you're not careful removing the small cover. I had a thermostat freeze up on my first Johnson Sail Master which caused engine to get so hot that it burnt and constricted water flow through a small 49 cent fiber bushing between the water intake tube and the power head. The whole power head had to be removed to get at this bushing which was a very expensive job. Here's a picture of the parts.
