Alternator belt question

[Kevin Henderson]

Aboard Pau Hana I have the required alternator mounting bracket upgrade with an upgraded Alternator.  Wanting to keep a replacement belt on-board for a spare, I tried to see what the existing belt had on it for markings so I could get a correct replacement.  Some of the lettering was worn and I'm uncertain as to the identifications markings on Alternator belts.  However, If I could get some help deciphering the folowing it would be greatly appreciated and maybe offer some brands or favorites.

Super HC Vextra
V80
30x400
72-0

[Mike and Joanne Stimmler]

Kevin,
I'm not sure what the numbers mean on yours but the numbers on my belt are
Gates 7400XL 11a1015

Hope that helps,
Mike

[Stu Jackson]

The 7400 is the length, the rest of the numbers are essentially the width, 3/8"

I went through this when I upgraded my alternator bracket.  The 7390 that came with the bracket was too short and the alternator ended up hitting the oil filter.

I wrote this up somewhere, I'll try to find it for you, and add it to this topic.

There's also a wiki on the subject.

[Stu Jackson]

November 2006 Tech Notes :Alternator Regulator Replacement

Belts:  As noted in Jim Moe's article, the 7400 belt works.  It's a bit longer than the old 7390 belt we used on the OEM alternator.  The shorter belt didn't work with the new alternator because it kept the inboard side of the alternator too close to the fresh water hose which rubbed on the top of the oil filter.  This was also true of the OEM alternator, and the longer belt will provide better clearances.  With the 7400 belt, there is still plenty of room to the door to the head, and the hose and filter are clear.  I carefully reviewed the Message Board posts on belt dimensions and the 3/8" belt is still fine.  The 3/8 inch belt numbers are: Gates or Car Quest 7400 – 11A1015; Goodyear #15406 – 11AV1015.  Jim Moe notes that belt selection is critical for the power being carried when the alternator is producing its maximum output.  It has to be the heaviest duty belt available and should be "toothed" on the inside to enhance cooling.  Don't choose to be too frugal and get a less expensive FHP 3/8" belt which is much cheaper at Ace Hardware.  We recommend high quality belts.  Always carry a spare belt.

FWIW, none of us has answered your original question.

The answer is:  take that info into any reputable auto store and they'll find the equivalent.  Add to that our input, and you'll find the right one.  Buy TWO, and write down what you bought.

[Ron Hill]

Kevin & Guys : Hard to tell what size belt you actually need if you don't have the OEM stock alternator !!!
It's the differant pulley that could change everything. 

If you have a belt that fits, take it to an automotive parts place and have them put it on a "belt measurer" and they can tell you the length of that belt.
 
The drive and internal water pump pulleys are made for 3/8" a width belt, but a 7/16" belt will also fit.

[Stu Jackson]

Maybe helpful:  http://forums.catalina.sailboatowners.com/showthread.php?t=135485

[Ron Hill]

FYI, the last NAPA belt that I purchased was made by Gates. 

For the M25/M25xp/M35/M35BC engines your drive belt will be between 39.5" and 40.5".  The variation is from the OEM alternator and the Hi Output alternator and the pulley sizes.

Like I mentioned most auto stores have a belt measuring tool - use it when in doubt!!

As I mentioned before, best keep a spare on board because MANY auto stores no longer stock "V" belts. Most autos have mainly gone to serpentine belts so they may no longer keep the size"V" belt you need in stock!!!