Temperature Warning Beeeeeeeeeeeeep

[Schnidly]

Hi Forum, I own a 1988 Mercury 90hp 2 cycle outboard, serial number 0B302485. Had an issue last year where the long beep for over temp was going off so I replaced the t-stat, poppet valve, water pump, bought a used warning module etc........ The t-stat and poppet have never been replaced before. I also replaced the temperature sensor. Well this was last fall. I had not run the boat since I had done this work. Fast forward to yesterday when I took the boat out for the first time this season. I managed to get around the lake a couple times without the beep going off. On my way back to another lake just idling along the beep started again. It would sound intermittently, long steady beep then it would stop, then happen again at varying intervals. My guess is that the USED alarm module I installed was not good or faulty. Can someone please give me a heads up on what might be causing this. I have a good pee stream coming out of the engine.

 

[Texasmark]

Well sir you hit all the nails except your impeller in the water pump. Follow the pee stream hose back to the engine and you will see that it emanates from the plate on the port side of the engine which is the water jacket cover for the exhaust. Water is fed to this area 24/7 and is not controlled by the stat which controls combustion chamber temps. A worn out impeller can cause your problem assuming your new parts function as designed. On your laps you mentioned, if you were running at a pretty good speed on your laps and over 2500 rpms your poppet valve was unseated allowing more (available) water to flow through the powerhead and you had some ram pressure of cooling water from the engine moving through the water at a higher speed so it could mask a lazy water pump.