My friends 1989 225 Johnson runs with head temps around 100 degrees. His plugs always look oily and fouled and has very poor fuel economy. Along with all of this his engine is very hard starting when it has not been run for a day or two. I suspect the engine is not running hot enough and keeping the plugs oily and this is the reason for poor fuel economy if there is such a thing as fuel economy on a boat. I believe the hard starting may come from a low spark paired with the dirty plugs.<br />My main question is what temp should the engine be running at as when we check it with a heat gun it is 100 degrees. I removed to check what I thought was a thermostat to find some type of diaphram that simply looks like it just restricts water flow. How does it control the temp?<br />Thanks for any help.
