Assesory Drive Belt Tech?

[MVCaprice]

I have a few questions on main engine accessory drive belts. The belts on the mains were shedding a tad so I am replacing them before the boat heads north for the summer. Also, I am not sure that the previous owner used the right belts so i am looking into better solutions and possible upgrades.

The setup on each motor is as follows: On each side there are two drive belts. There is a single alternator on each engine. What I pulled off are Napa 25-7470 belts which are cogged 1/2" x 48" A style V-belts. They are a bit loose so i am considering going to a 47".

The questions i have are basically as follows:

1) Do I need to run cogged style belts? The pulleys are not cogged.
2) Can I / Should I upgrade to Kevlar?
3) Since these are dual belts, should I get a banded style A belt? Did Detroit use banded belts originally?

 

[racclarkson@gmail.com]

Maybe check the alignment of the pulleys first thing?

 

[MVCaprice]

Maybe check the alignment of the pulleys first thing?

Alignment looks good. Its just age primarily. They are at least 7 years old.

 

[Top Hatt Craig]

The “cogs” on the inner surface allows increased flexibility for small pulleys and still have good centering and fit. Kevlar is good as long as the belts are otherwise well made. I doubt if your alternator pulleys are small enough to need clogged belts but don’t really know, there’s no drawbacks to the design. Twin belts should only be purchased in matched sets (two belts per package) to insure long life.

 

[Boatsb]

I get pairs for running on twin pulleys. If not one wears while the other Is too long.

If they last 7 years go with what you have. No need 5onchange if it works

 

[MVCaprice]

It looks like on one of the engines someone replaced one belt and not the other. Pretty dumb move. I'll stick with the cog'd napa belts for now.

Thanks for the feedback.

 

[MVCaprice]

So I ended up buying the same sized cogged belts from https://www.vbeltguys.com/ . I received them in a swift 3 business days. I also only paid 7$ and change for each belt which seems to be an amazing deal.

After comparing the new belts to the old, I am very surprised how much the old belts stretched. The new belts look about 1 inch shorter. I guess that explains why I kept having to readjust the tension!