Engine Drive Belt Size - M25-XP

[britinusa]

When I did all of the work on our Engine Electrical / Exhaust System, the drive belt was very suspect so I replaced it with one that was a spare when we purchased the boat a year ago.

There were 4 spare belts, each a different size/brand/type.

The only one that fit was a Napa Premium XL 25-7405
It is a V belt with the notches in the inside.
Here's a link to it on the Napa Site https://www.napaonline.com/napa/en/p/NBG259348M/

It Fits! but is it the correct belt type?

Paul

[Footloose]

If it fits I would go with it.  There seem to be many configurations and pulley sizes that I don't think there is a right or wrong belt as long as it is the right length and width.

[KWKloeber]

Paul,

As I said in my email...

While many like NAPA belts, with the small pulley sizes, my Westerbeke parts distributor recommends a Dayco Top Cog belt.  It is supposed to run cooler that a bottom cog belt while the top cogs provide more flexibility on the small pulleys.



First check that, with the replacement alt, the belt width and angle fit correctly.  A new belt should fit to the top edge of the pulley, not above or sit into the vee.  If that's ok, then look up the belt width/angle or a NAPA dealer should be able to find that, and check for the same size/width/angle from Dayco.  The better Dayco Top Cog Gold is a step above, but I haven't seen them (yet?) in the width/angle for our pulleys.  The Dayco site has a belt locator by plugging in the length, I don't know why, but with the alt bracket betterment, I recall some discrepancy as to the proper belt length.  Maybe it's on the cusp?  This is what I have:

Dayco Top Cog 15390
Effective Length (in) 39
Angle 36
Top Width (in) 0.44
Metric Part   11A0990
Outside Circumference 39.57

-kk

[Ron Hill]

Paul : The length of the belt depends on which alternator you have and its pulley? 

As I remember the original length was 395? (which is 39.5 inches)

Ken is correct on getting a belt with the cogs on the top - helps cooling.

A thought

[KWKloeber]

As I (forensically) justify it to myself to explain why the top cog is better, is that the full-surface contact with the pulleys reduces slippage (thus heat and belt dust) and also provides more surface for heat transfer.  The top cogs provide the flex necessary when going from a bottom cog to a solid bottom belt.   

That's my story and I'm stickin to it (unless someone has 'nother better idea.)

-kk

[lazybone]

Agree with KK.
I'm not sure that they are still relevant but Ample Power specs the Dayton TopCog (and only the Dayton TopCog)  for their alternators.
Its worth mentioning that many of the different big brand names are made in the same factory.   

[britinusa]

Two of the spares I have (provided by PO) are top cog but I'll have to check if they fit.

Paul