Pontoon Boat & Deck Boat Forum

I have a mid 90' merc 50 4 stroke Lately the little horn connected to the console has been sounding. so far at slow speed. I turn the engine off restart runs quiet then noise. Lots of water out of the engine I haven't connected the temp gauge yet All else sound good Thoughts ???

Time for new impeller. Flush system also.

The impeller will probably fix it. If not the thermostat and poppit valve may need to be replaced. I had an alarm earlier this year on low to mid rpms and it was after I had replaced the impeller a couple months earlier. Changing the thermostats and poppit fixed it.

Thanks !! but what's a poppit ?

The poppet valve regulates water pressure in the block. At idle your water pump barely pushes water through the block, especially through the top cylinders. When you increase rpm's the water is forced through the motor by a combination of the water pump and the force of the water pushing into your water pump from forward motion in the boat. The poppet valve will open when the water pressure in the block becomes too high and it relieves the motor of this extra water pressure by redirecting the water out the exhaust ports. If the valve is too weak or has a leak it let's water pass that is needed in the upper parts of the block.

Also possibly low oil pressure alarm. Change your filter recently?

Is the poppit easily changeable and where is it. I did an oil and filter change when I redid the bottom paint a few months ago.

On my motor (yamaha) it was easy. It took me 30 minutes to change the poppet and both thermostats with the boat still in the water.