AllDodge, Thanks a lot!!! You have been a big help. I have 2 dayco belts coming in the morning!!!

My 2002 8.1 0M084807 uses the same belt(8638761) for replacement. I should be going to my boat later this eve or Saturday and can get the Dayco number former owner used. Also I worked at Advance Auto and we have a tool to measure length. I would think autozone could also?

OK Bronco time to think outside the box. Take the bolt out of the front of the brass adjuster and take the brass square off completely. I remember on mine that the little ball on the end of the threaded bolt sometimes wouldnt align/seat and wouldnt let the alternator suck all the way in. With the exception of someone changing one of your pullies, it has to be an anomaly in the adjuster itself.

Any update on belt that worked? Mine had the numbers worn off.

Now that you mention it I had that same issue with the adjuster not also. Definitely something to look at!!

Mine is very difficult also. The only way I can get it on is to pry it up over one of smooth surfaced pullies with no lip last.

I ended up using NAPA part number 25-061120.

Hey Guys, just sitting here going thru all these posts. I’m in the same corner, ordered the replacement from Mercuiser and numbers match. The adjustment bolt/pin is backed off the bracket about an inch and the alt. Appears to be hitting on the top of the bracket for the power steering pump. The old belt was tight when I pulled it off and the new one refuses to go back on.
So question did anyone find a new Mercruiser part number for a longer belt. I’m sure I could make it go on by loosing tha idler pulley brackets but that would most likely put too much strain on the seawater pump and eat the seal out again which is the reason I’m in the mess to start with. ????

So I eventually ended up using the Gates RPM belt, (RPM is supposed to be their highest quality belt) hoping that it would not stretch as much as the lower quality gates belts. Anyway, it still seems to be stretching. I put straight edges on the pulleys and they are all aligned. So I've read that you have to keep watching the tension and adjusting until the belt settles in and is done stretching. I will try that for a while, but I'm still contemplating moving over to the auto-tensioner system of the newer model 496's. Roughly $500/motor. Anyway, it was not the adjuster block or bolt that was causing the alternator to stop adjusting inward. The alternator was hitting on the power steering bracket.

FBRONCO, what's the number for RPM belt?

thx