Trojan Boat Forum

Running 1974 Chrysler inboard M400's where there are two belts running side by side in parrallel that are driven off the engine and drive both the alternator and the Sherwood D55 raw water pump.

One belt is fairly tight, but the other is extremely loose.

I noticed my voltage gage acts erratic and I have been running hot 190 instead off expected 160).

Can belts cause overheating? Anyone seen this?

A slipping belt could . Now if both belts run exactly the same things ( no more no less) They need to be a "MATCHED SET " . Both belts should be close to the same tightness . With one lose and the other one tight your asking one belt to do the job of two . Finding a matched set some times can be fun ,its more then pulling 2 belts off the shelf with the same part numbers . You need a real parts store avoid chains where all the know is whats on the computer . ( NAPA is OK ) .

Makes sense. Thank Prowlerfish.

change all my belts, which was interesting because on the Chrysler there are two belts running in parallel:
Over the pulley at engine center, over the alternator, and then over the water pump pulley. Tension set by alternator position.

With 2 new belts I had trouble getting them both tight - appears groves in pulley has worn at a different rate, or likely the
variation in belt manufacturing allows one to stretch more. I installed, ran for 10 mins and retightened them up. Took her for a ride
and.... no more over heating!!!!!!!

I had to make them very tight in order to avoid one being loose. I also noticed slippage during my tests. I marked the belts and after running
I noted the belts have slipped and no longer are in the relative position when installed.... is this normal?

None the less, I believe I can say my over heating is behind me now.

Would it be possible in this case to use single belts ,one to drive the raw water pump,and the other to drive the circ pump ,alternator side---- if your alternator is under 80 amps or so one belt should be fine---- that way you can adjust at will,might have to shim a bit to line up pulleys but seems doable---- Mike

have you checked to see if the water pump and or alternator are mounted square with the crank pulley ? I am not sure how the water pump or alternator is mounted on you engines, but I know on the sherwood pumps on my crusaders, you can easily not have the pulleys aligned square with the crank pulley and you have to pay attention to that when you install and tighten the pump and belts.