Overheat alarm?

[Jburke]

Last time I had the boat out I had some problems with what I think was overheating. Did fine until I headed back to the launch. Hadn't really used the motor much, just running from different spots on the river but there was a lot of seaweed in the water. The motor worked fine and then reduced down to almost an idle speed and the alarm sounded. Shut the motor down but when I started it again it seemed to be working properly with no alarm after that but it didn't seem to have it's usual power. Still spitting water, but I didn't think to check that until I made it back to the launch. Any ideas from you guys about this, clogged cooling system possibly?

[99yam40]

when was the last time you replaced the water pump and thermostat.

And We have no idea what motor we are talking about

[Jburke]

Sorry forgot to mention that. It's an 02 40hp four stroke. I have not replaced the water pump or the thermostat. I just got the boat this last spring and have only changed the oil, lower unit oil, fuel filter, and plugs.

[99yam40]

I have seen rubber impellers damaged by blocked off intakes , so I would replace it and at least test the thermostat if not replacing it just to be sure

[Jburke]

How easy is it to replace the impeller? I was thinking about replacing the thermostat just because I have no idea when anything was done to the motor and with it being a cheap part it just makes sense.

[99yam40]

A Yamaha repair/service manual will help you out while working on your motor for years to come, get one and read up.

2 strokes are easy but I never did a 4 stroke so I can not say.

[Jburke]

I'm going to pick up a service manual in the morning and take a look. Just need to get things figured out soon, got an important trip coming up in a couple weeks!