Aligning alternators and engine pulleys, general principles

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Kit_L

Kit_L

Guru
Joined
Mar 12, 2016
Messages
535
Location
Australia
Vessel Name
Suu Kyi
Vessel Make
Custom 40' catamaran
A question to the tech gurus here, re. aligning or realigning alternators—how is any needed correction done? Shims? A judicious whack with a lump hammer? I do have straight edges. If there is a definitive thread on this process, please link!

The back story is that I lost an alternator belt of the starboard Volvo Penta KAD-300 while offshore in rough conditions. I have researched how to change the two serpentine belts, and how to torque the adjusters. The top pulley has to be removed to access the alternator belt, but I decided to replace all three (two serpentine, one alternator) as I had the spares.

I have noticed alternator belt dust before, so suspect misalignment is part of the problem. All responses gratefully received.
 
Before solving the problem, determine one exists. The 2 serpentine belts on my JD gave off some dust, regardless of the alignment being perfect. The two original belts were still on the engine after 6,000 hours. They were both 8 groove belts running well below half of the allowed load. Belt failures are sometimes alignment, but often loading close to the limit.

After checking the alignment, post some pictures of the offending accessories to better answer how to correct them. Also it's important to understand whether the pulley is in a different but parallel plane or the pulleys plane isn't parallel to the crankshaft pulleys plane. Hope I made that clear.

Ted
 
Ted, thanks, and perfectly clear. I wasn't clear—the serpentine belts are fine, and no dust, but because the outermost one and its pulley has to come off anyway (to get to the alternator belt) I decided to replace both. The ordinary fan-belt type of belt that spins the alternator is the one that's throwing dust. Because of the confined nature of these large engines in catamaran hulls, it's very difficult to get a clear view to check the alignment of the alternator pulley with the crankshaft pulley.
 
It’s common for alternators to throw dust if they are heavily loaded. Single belts especially.
For alignment, I use a small tool with a laser embedded in it. Essentially it’s a chunk of v belt with the laser in it to shine over to the next pulley. It takes a little practice with it to get good at using it, but it’s super handy.
 
Bmarler said:
It’s common for alternators to throw dust if they are heavily loaded. Single belts especially.
For alignment, I use a small tool with a laser embedded in it. Essentially it’s a chunk of v belt with the laser in it to shine over to the next pulley. It takes a little practice with it to get good at using it, but it’s super handy.
Click to expand...
That sounds pretty interesting. Could you give some more info about the tool? Is it a commercial product?
 
The website "Marine how to" has a fantastic article (Marine alternator installation-tips and tricks) that talks about what you are looking for.
 
Mac2 said:
The website "Marine how to" has a fantastic article (Marine alternator installation-tips and tricks) that talks about what you are looking for.
Click to expand...
Ah, found it, thanks! I think that site will be getting some reading hours over the next few days...
 
Found the link (after a while):

marinehowto.com

Marine Alternator Installation - Tips & Tricks - Marine How To

A Fresh New Alternator For many boat owners the task of upgrading their engines alternator can be intimidating. It does not have to be, and this article will help you understand how to do this job correctly. It includes numerous professional
marinehowto.com
 

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And that gauge sounds perfect—I'll but two, and give one to my favourite mechanic!
 
marinehowto.com
I don’t know how to link. If you go to the site, the article to look for is below.
 

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I found the link, eventually, and read the whole article; very detailed and precise. His recommended method for checking alignment seems very sound, and I'll use that (clamping straight-edge to crankshaft pulley) if there's enough room to do this.

Note: he does not recommend the laser gauge.

To set the v-belt tension accurately, I bought a Gates 91132 Krikit V-Ribbed Belt Tension Gauge from Amazon. I have a torque wrench and the factory tension settings for the serpentine belts for the Volvo Penta KAD-300 engines we have. I think I'm set!
 
MVCalypso said:
That sounds pretty interesting. Could you give some more info about the tool? Is it a commercial product?
Click to expand...
This particular tool is very inexpensive and does a pretty good job. I had to fiddle with the laser and battery holder a bit but it’s working fine now.
I don’t think I’d spend the dough for the gates laser tool, this one is good enough and is invaluable when there’s no room to get a straight edge in position.
 
Hmm, the link has changed somehow. It worked when I clicked on it though. I wonder what that’s about?
If the link doesn’t work do a google search for “hog slat laser fan belt alignment kit”
 
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I replaced the supercharger and alternator belts on the starboard engine today. Bought a torque wrench and used this to tension the serpentine belt; seemed to get the tension perfect. I was was going to use the "Krikit II" tension gauge on the alternator belt but the raw water piping is in the way, so used the 'tighten until you can only deflect the middle of the belt 10mm' method. I'll give the boat a run tomorrow, and re-check tension once the engines have cooled down. I'll be getting more spares, too! Alternator pulley alignment looks fine. The belt that broke offshore was probably just old.
 
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