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Old 07-18-2020, 09:14 PM   #1
Join Date: Jun 2020
Location: Huntsville, AL
Posts: 2
Default Mercruiser 4.3 Shredding Belts \ Pulley Alignment

Hey all,

Sorry of the length of this post, but I need some advice on how to proceed. I don't know a lot about engines, but have an engineering background and do a lot of my own maintenance on our cars. I recently purchased a 1997 2000scl with a Merc 4.3. We took her out a few times then on the 3rd time, she shredded the serpentine belt. I had the marina mechanic replace the belt to see what would happen and two outings latter she shredded the belt again. I looked at it briefly and to me it looked like either the power steering pump or alternator was out of align. I told the marina to have the mechanic take a look to figure out which one and fix it.

Two weeks later...

I talk to the mechanic to get an update and he says it is the alternator out of align, but he has yet to figure out what the previous owner did to get it out of align (PO did replace the alternator fairly recently). I go to take a look this morning. Here are my observations from this morning:

First, the belt that is on there seems too small. The idler pulley is all the way down (no way to loosen the belt anymore using it). I wanted to remove the belt to look at the alternator. I loosened the nut on the idler pulley some to try to get a little play in it and I think I could have used a screw driver to slide it off the water pump pulley, but have no idea how I would get it back on. The correct belt length seems to be 2197mm, this belt is 2194mm. Gates has a 2200mm belt. I feel like the 2200mm might be a better fit and give some room to adjust it. Do you think this belt would be too long? Guess I could just go get it and try it.

Second, I think both the alternator and p/s pump are out of align. I took the straight edge of a level and laid it across the crankshaft??? pulley and the idler pulley. The two aligned perfectly. The same wasn't true of the alternator or the p/s pump. The alternator pulley has definitely been pulled toward the engine block. It was hard to get a good read on the p/s pump because the pulley has a little lip, but looking along the straight edge of the level, I could tell there was some tilt toward the engine in this pulley as well. Is this a decent test? It at the very least, both pulleys seem suspicious to me.

Third, I pulled up a parts diagram I found at:

I wanted to try to see if maybe the previous owner had forgotten to replace some washers or something when he installed the alternator. The only thing that jumped out at me is that on the back of the p\s pump the the PO had placed two washers where it looked like there should have been some sort of spacer, but according the parts diagram, that stud shouldn't have been there to begin with (which as I am typing I realize maybe I need to go remove this stud as the torque applied to it may be pulling the power steering pump out of align???).

My working theory is that previous owner put a belt on there that is a little to small. When the belt shredded my mechanic just took that belt and got one of the same size. Having the little too small belt overtime has bent the alternator bracket and possibly the power steering pump bracket causing them to lean toward the engine. But the belt is only 3mm too small, so I don't know how good of a theory this is. I plan to call the mechanic next week and don't want to sound like an idiot. Is this theory crazy? Is there something else I may need to check?
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