I have a 1986 Yamaha V4 115hp, My oil resevoir is full, But after running for approximately 15 to 30 minutes the alarm sounds at the console, and I can not run it over 2000rpms,(like its suppose to when the alarm sounds) but if I turn off the boat, and wait about 15 minutes, it will start back up and run fine, for a little while, and then it happens again. Also, sometimes there is exsessive smoke coming off the engine, sometimes its so bad it looks like the boat is on fire. I have replaced the impellar in the lower unit, so I don't think it's over heating. It's an outboard motor, and I have it on a 24 foot pontoon boat. Any help would be greatly appreciated..stilesdm