Drive belt woes

[britinusa]

We missed out on the New Years Eve Cruise because of a horrific Squeal from the alternator and the pulley was too hot to touch even after less than 2 minutes of engine running (we shut it down once the sound was identified and restarted it with the steps out in order to locate the sound)

Initial thought was that it was the Alternator Bearing - but the alternator is only 7 months old. I took it to a local Alternator shop and they tested it, bearing are perfect and the 100A alternator was loaded to produce 140A during the test, quiet as a mouse - definitely not the bearing.

I took the drive belt with me to the shop and asked them to inspect it with more experienced eyes than mine, as I pulled it from the bag the tech's 1st words - Wrong Belt! The alternator has a 1/2" pulley and that's not a 1/2" belt! General consensus is that Belt Squealed because it was slipping -

When I purchased the boat in 2015, I took the belt info and purchased 2 spares matching the original. The belt is 13/32"

Back at the boat, I measured the Crank Shaft Pulley and the Coolant Pump Pulley - both are 13/32" I also measured the Original Alternator Pulley - 1/2"

Choices: Replace the alternator pulley with 13/32", Replace the 2 engine pulleys with 1/2" or get a belt about 14/32"

Now, why did it slip? Belt Tension!

I'm pretty certain that this is the issue. The Alternator Support Arm (pic attached) has the tensioning slot and the spring washer that is between the arm and the bolt head has spread.

My solution: Make a plate to cover the Arm Slot, bent around one side of the Arm to prevent rotation.

Paul

[Ken Juul]

A fender washer of the correct size will also work.  The "spring" washer is also called a lock washer.  Get them both at Ace for less than a dollar.  Good luck on your search for a new pulley.

[britinusa]

Thanks Ken, the guys at the Local ACE store know me by name and I know most of them, always helpful

Bolt, lock washer, fender washer, all for $1.75

:)

Paul

[Jeff Kaplan]

I really don't think that the 3/32nd difference in belt size makes that much difference. At the end of last season I too heard a loud screech from the engine and it turned out to be the fresh water pump froze thus causing the sound, check the water pump pulley and make sure it is spinning freely, if not, I'll agree that the belt tension is not correct. Fully tensioned, the belt should have a slight deflection of about a 1/4" when you push down on the belt, just make sure its tight to the touch, too much slack will lead to the screech. Good luck, my season is long over, major blizzard today in New England.

[KWKloeber]

Paul,

Notice that the underside of the capscrew head is rounded, which is causing the lock ("spring") washer to spread.  Switch to a hardened hex bolt.  Make sure they match size.

What belt were you running?

Ken

[KWKloeber]

By rights it should have a nut/lock washer (or nylock nut) on the back side, and not rely on the crappy alt case to keep it from vibrating loose.

[Ed Shankle]

I agree with Jeff. Had the same thought from the description. Don't overlook checking that out.
Regards,
Ed

[KWKloeber]

If the wrong pulley is on the alt, it may also have a different belt angle spec.

[Noah]

When I upgraded my OEM 55 amp. alternator to 95 amp. I reused the pulley off of my old one to make sure it was a good match to engine. However, it maybe too late for you to try that.

[britinusa]

I'll talk to the shop that is servicing the spare Alternator about changing the pulley and possibly changing the pulley on the one that is on the boat.

Paul

[britinusa]

By rights it should have a nut/lock washer (or nylock nut) on the back side, and not rely on the crappy alt case to keep it from vibrating loose.

The 'block' that the Bolt screws into is blind drilled & tapped, so no screw threads beyond the block to host a NyLock nut.

Paul

[KWKloeber]

Paul,

1) mea culpa, I was actually thinking of another install where the arm is adjusted at the alt bolt/hole.  Different boat.

2) A no-thru hole is easily fixed, 'eh?  Then I'd use a partial (vs. a fully) thread capscrew (grade 5 if rounding is an issue as in your pic) followed up by a nylock.

3) have you seen this arm/adjuster? 
http://c34.org/bbs/index.php/topic,9212.msg69837.html#msg69837

Unfortunately, the "new arm" is very poorly designed (Wb? or Universal?) engineering/mechanics-wise, that is -- NO there.
There's excessive force needed at the arm slot/tightening bolt location because more of the work is being used for the arm to push the alternator AWAY FROM THE pivot/mounting bolt, and less work is going into rotating the alt ABOUT its pivot point.
The alt mount/pivot point should have been placed further to port (more material and welding = more cost  ), and the alt sitting so the pivot is near 12:00 position.  Then, the adjuster would be putting work into rotating the alt, rather than pushing it sideways.

k

[Ron Hill]

Paul : Take the bolt that threads into the block thread and see if you can get a longer bolt so that more threads are engaged (I did that to all of the alternator bolts that threaded into the block on my engine).

Most alternator pulleys are a wide "deep V" to accommodate for engagement and wear.  Are you sure it was not just a slack adjustment? 
If you don't have an alternator adjusting tool - GET ONE.  Look in WiKi for that where to get that tool.

A few thoughts

[britinusa]

Thanks Ken, yes I saw the earlier post about the adjustable Alternator arm - beyond my skill/tool set!

But I did see this too: https://www.ebay.com/i/291829076699?chn=ps

I'll look at drilling the bolt hole all the way through the bracket and then adding a nylok.

Ron I didn't find the Wiki reference for that tool, is it like the one I link to above?

Thanks.

Paul

[Stu Jackson]

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I didn't find the Wiki reference for that tool, is it like the one I link to above?

Thanks.

Paul

Paul,

It's in the Critical Upgrades.

Yes, that's the thing.