Re: Force 120, pumps water but overheat buzzer is going off Yes, it can overheat and be pumping plenty of water. Remove the back cover at the top of the head and check the thermostat. It may be stuck closed, partially open, or broken. I just went through this on a Chrysler 105-the one in the avatar.

Mercury Force 120 Manual Cooling Systems

Force

It would overheat at idle but cool down at full throttle. The thermostat was broken on top where the bar from the expanding pellet pushes. Since the.&^%$ cover would not come off, I had to replace the head. Since the only head I had was off a 140 with a 3.375 bore, compression dropped from 135 to 120. Service and repair manual mercedes 220se. Now my project will be to drill out the bolts and re-tap the holes so I can re-use the smaller combusion chamber head. Re: Force 120, pumps water but overheat buzzer is going off NO! I would strongly suspect that the previous owner removed the thermostat because of a heat problem.

Now it is yours to diagnose. Before you start though, run the engine until the overheat alarm sounds and then a little more. Dribble some cool water on top of the block. If it rapidly boils off the engine is overheating. If it gradually evapoates, then the buzzer is bad and the engine is running at its correct temperature. Can you smell hot paint when the buzzer is sounding? If the engine is really running hot: Remove the lower unit and try to blow water up the brass tube.

If it is free and water flows freely out the thermostat hole then you need to remove the exhaust cover and check for sand or corrosion build-up inside the exhaust jacket. While you are at it you may as well remove the head and check the cylinder water jackets too. Check the cooling jacket inside the head for build-up. Before starting be aware that you most likely will snap a couple of bolts unless you are very lucky. Re: Force 120, pumps water but overheat buzzer is going off Hey Frank Ran the motor on a set of muffs for 15 minutes and the alarm did not go off. I sprinkled cold water over the top of the block anyway and it did not boil off or look even remotely affected. I touched the block and id did not feel to warm.

Yesterday it went off in about in about 5-10 minutes of use on the river. I have a thermostat ordered, but am not sure of the right way to put it in as there isn't one in there to tell the correct way.

All of the pictures in my manual show different direction. Thanks again for the help, you really are the Force guru. Re: Force 120, pumps water but overheat buzzer is going off Sounds like the thermoswitch on the head is too sensitive. As faras the thermostat, USUALLY, corect installtion is with the pellet toward the hot side, the block However, on olde Chrysler engines there was not enough room and it went in opposite. If you have enough room install it with pellet toward hot side, if not, put it in the other way.

120 Force By Mercury Marine

In either case, there will be a bleed hole either in the thermomeer flange or a small notch cut in the hole where the center seats. Install with this bleed hole up so hot water will tend to wash over the pellet.