1987 3.0L Mercruiser Alternator Belt Always Comes Loose

[Searay87]

Sorry if this is an old topic but I couldn't find a thread that deals specifically with a chronic problem I have with my alternator belt coming loose about every 8-10 hours of run time. I check it every time I go out or on occasion I'll hear it squeal when the engine starts so I tighten it. A 5 minute job and it's not that difficult. Of course I learned the hard way as I had a belt shred on me and ened up paddling to shore and calling for a tow.

I'm selling the boat to a co-worker who isn't at all handy around engines and I 'd like to solve the problem. I've replaced the lock washers, I've tried those little star washers that dig into the metal guide but the alternator continues to come loose.

Is this simply a characteristic of these engines? If not does anyone have any advice on how I can solve it?

Thanks!

 

[fmalott]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

i would almost think that the alternator is not mounted right and there is to much shaking. i remember reading a previous thread from someone that had the same problem and it end up he didn't have enough mounts he end up adding another mount and solved the problem. when you start the engine and let it idle look to see how much shaking the alternator does and also try when WOT

 

[Searay87]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

Thanks for the reply. Not sure what to say about the mounting. There are only two attachment points and I've since replaced the alternator and the same problem persists with the new one. As for the shaking while it's running everything looks normal at 3500 RPM which is the highest I've run it.

 

[Bt Doctur]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

I doubt the alt is coming loose,more like the belt is wearing too thin and dropping down in the pully. try using a wider size, maybe a metric size belt. The squeal is the tip off , either a loose /worn belt or alt/battery/ charging problem.
Yanking a belt tighter only causes more damage

 

[Don S]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

Bet money your pulleys are rusty. That rust acts like sand paper and will wear out a belt in no time.

 

[Searay87]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

BT Doctur: You may be right as I have noticed a minor amount of wear along one edge of the belt. It's the same belt for the past two summers and it's not getting any worse. I still think the alternator itself is slipping because of how slack the tension gets.

However at this point I'm willing to try anything. Does a belt with v-notches in it as opposed to a continuous or solid belt make a difference? The actual belt has v-notches.

Thanks
Bob

 

[Searay87]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

Don: I've read your former posts about rust and I don't think that's my problem. The main reason is I had the same probelm with the old and new alternator (re: fresh pulley) and the pulley on the engine looks good with the black paint still intact.

I've posted a couple of pictures. Note the right side of the belt is worn off and isn't seated properly in the pulley. What is causing this?

 

[fishrdan]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

Are you tightening the bottom bolt, along with the top bolt?

 

[Searay87]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

fishrdan: Yup. I loosen both then snug using a pry bar to tension the belt and then tighten. I can't explain the uneven wear on the right side of the pulley. Is this an alignment problem or do I have the wrong size belt? Another thing that puzzles me is I had the same problem with my old alternator. I should add that the belt is common to both alternators.

A little bit of background: I purchased the boat in need of a new alternator belt. I had it replaced by the local Mercruiser dealer. This new belt shredded as I was unaware of the meaning of that loud squeal. It came and went so I ignored it. Eventually the belt disintegrated and it was replaced a second time. Since then I've kept an eye on the tension. The old alternator failed and I replaced it myself and kept the same belt. Re-tensioning the belt every 8-10 hours of running time.

 

[fishrdan]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

Missed the pics, that's one shredded belt. Check the pulleys for rust as DonS suggested. Maybe an alignment issue or something dragging on the belt if the pulleys are clean? (Pulley in the first pic looks rusty)

 

[Don S]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

I can look at all that black belt dust on the engine and tell what the problem is. You didn't show the all the pulleys and even the one you did wasn't the area where rust is.
Th rust is on the inside of the pulleys where the belts ride.

 

[wrestling coach]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

Check your pulley alignment as best you can. If you replace the belt try a Dayco Top Cog from Autozone.

Dennis

 

[Searay87]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

Ok thanks for the input. I didn't show the inside becsue I didn't see any obvious rust. I'll loosen the belt and inspect more carefully tomorrow. What do you recommend for cleaning the pulley surfaces? Is there a thread with a procedure you can point me too?

Don: Can you comment on how the right edge of the belt is sitting in the pulley surface of picture #1?

 

[81 Checkmate]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

If your belt is wearing on one side... it is one of two things..

The pulley or pulleys are badly rusted on the wearing side and causing the belt to wear... then split ...then break. As Don sugested.

Or... you have an alignment issue. When you are adjusting the tension... snug the bottom bolt then use your pry bar and adjust the tension then tighten the top bolt that is in the slot..... then tighten the bottom bolt.

If the belt was to big (Wide)... you would think it would wear on each edge.

Glad to see somone that is fixing the problem before passing it on to someone else.

Good luck!

 

[bobhol]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

I had tons of black dust from my belt and I kept adjusting it till I realized it was out of alignment with the center pulley ...a couple of washers as spacers did the trick and the new belt is wearing fine and no more dust!!! by the way I ended up using a notched belt cuz it was available on a Sunday...Good Luck

 

[Searay87]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

Ok so I'm glad I didn't bet money with Don. Rusty pulley it is. Thank you! Now for some more newb questions. I'm trying to remove the belts following the procedure Don gave me 2 years ago. I've removed the spacer block. Check.

When I loosened off the power steering belt I wasn't able to slide it off the pulley because of the lock nut and washers on the center engine mount as shown in the picture. I tried loosening the pulley bolts but they turn the belts. Am I missing something? Is there an easier way to do this? It looks like the alternator belt would come off the same way. Can I remove the lock nut and washer on the front engine mount and not cause any other problems? Help!

Thanks

Bob

 

[fishrdan]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

When I loosened off the power steering belt I wasn't able to slide it off the pulley because of the lock nut and washers on the center engine mount as shown in the picture.

Well, Ain't that a.....

I'd loosen the water pump pulley bolts so you can rock the pulley away from the front mount. An impact gun in reverse would spin them out quickly. Or, use opposing wrenches to loosen the pulley bolts, once one is backed out 1/2 way you can use it for leverage (wrench on another bolt then resting on the 1/2 way removed bolt) to hold the pulley tight. Don't back the bolt out too far or you could strip the water pump flange threads, or just use a longer bolt for the leverage bolt.

Those pulleys are going to be fun (not really) to sand. I'd use some 120 grit to get them sparkly clean, then hit it with several light couple coats of quick drying spray paint. Rustoleum would be the best bang for the buck paint, but I think it would take for ever to dry so the belts didn't chew it off, probably a week or more. Maybe DonS has a recommendation on which paint to use, that wouldn't take for ever to dry.

Oh yeah, zip tie spare belts to the motor mount while you are in there, so replacing a belt isn't such a pain if stuck on the water.

 

[Searay87]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

Hey fishrdan: Thanks for the advice. I'm not very mechanically inclined so you'll ave to bear with me. I have no power tools. I don't know what you mean by opposing wrenches on the pulley bolts. Are they reverse theaded? Would it be possible to use a block of wood to prevent the pulleys from turning while wrenching the pulley bolts?

I have a copy of the engine manual and in the power steeing section they mounted the belts before they installed the front mount assembly. There's got to be an easier way of doing this. I've read other threads where they discuss loosening the engine mounts and lightly jacking the engine? Without pictures I'm lost.

Thanks

Bob

Follow-up: Found this on-line:

As for how to change the belt, you need to block up the motor, remove the power steering belt, remove the two motor mount bolts (port side) and the spacer. Loosen the alternator. Feed the belt through where the spacer was, put belt on centrifugal water pump pulley (lower) and top pulley, and alternator pulley. Replace spacer and engine mount bolts. Adjust tension on belt and tighten down alternator. Some people suggest feeding a spare belt through while you have the engine bolts out and zip tying it to the spacer, so that the next time the belt breaks, you don't have to go through the hassle of removing the mount bolts.



Read more: how do i change the alternator belt on my Crownline boat, Mercruiser - JustAnswer http://www.justanswer.com/boat/244y...-crownline-boat-mercruiser.html#ixzz1wamHP8wj

DO any of you experts recommend this procedure?

 

[achris]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

.... Not sure what to say about the mounting. There are only two attachment points and I've since replaced the alternator and the same problem persists with the new one. ....

There should be 3 (one on the top, 2 on the bottom)....

 

[Don S]

Re: 1987 3.0L Mercruiser Alternator Belt Always Comes Loose

First, remove the outdrive. You don't want to be jacking up the engine and putting a strain on the coupler.
Next, borrow or rent a "Port a power" and use what ever ram you can get under the pan with a 2x on top to protect the pan.
Remove the lag bolts holding the front motor mount to the boat.
raise the engine enough to get the weight off the mount. and remove the mount.
Now, either remove the dampner sand, clean, prep and paint with rustoleum several coats per instructions on can. Let dry for a couple of days if you want it to last for more than 5 minutes. Do all the pulleys.
Clean that mess off the front of the engine and timing cover and prep for painting so it doesn't rust through too. Paint as needed.
Put it back together.
Check the engine alignment with the alignment tool, re-install drive with new gaskets after you check the bellows, gimbal bearing etc.

Now, you can go boating.