Need help with 25 hp mariner

" 1995 25 hp mariner. After ru

" 1995 25 hp mariner. After running about 20 min at close to full power i cut the moter for about 3 min. When i restarted it would crank and idle, even rev up in neutral, but when i put it in gear it would die. This went on for about 15 min. Finally i took the cover off cranked it up, put in gear and it ran fine. What could have caused this? Could it have been too hot. Should i replace the impellar?
It also runs a little rough at an idle.
The boat is new to me and this was the longest continuous run I had made with it. "

" Greg,

If the engine is ru

" Greg,

If the engine is running too hot you can tell by touching the exhaust cover plate on the port side of the engine. If this gets too hot to touch without getting burned it is running too hot.

If the water jacket cover on the rear of the engine is getting too hot, and the exhaust cover seems okay, then the thermostat is probably not working.

Usually, if the engine is running too hot it has something to do with the water pump, but other things can cause it to run hot. If the gaskets in the exhaust system are leaking, or the powerhead base gasket is leaking, or there is a clog somewhere the engine can run hot. Sometimes the water tube form the pump is clogged. If you think it is running too hot, and the thermostat seems okay, the best thing to do is drop the lower unit. Then you can hook up a water hose directly to the water tube and see how well water is circulating. You can see if any areas are not being cooled by feeling the engine. It is easy to feel the cool water circulating. You can even run the engine like this and see if hot spots develop. If the engine does not cool when running this way there is a problem somewhere in the water passages. If the gaskets are leaking you might see some signs of water on the spark plugs. There should be heavy, gray deposits on the plugs, just like when you mix water with oil.

I would not rule out a fuel problem. The rough idle sugggests that you may have some debris in the float bowl. They used a few different carbs on these engines, but I think they all had fuel pumps that were part of the carb. If you decide to remove the carb for inspection, you might as well get a total rebuild kit and replace everything while you have it off.

Tony "