alternator belt replacement

garyw · May 23, 2014, 07:13:17 AM

hi

Sorry if this has been covered before but couldn't be sure I found it. Looking to replace my alternator belt but not sure where to go for the replacement. This is on my M25 engine 1986 with the new bracket. The current belt is a Fleetrite L15402 34289x2 are the numbers and it is fraying so I need to get a new one. I called a marine supply store in Michagan and they recommended a Gates 7390xl but not sure it is the same as what I have .

Thanks

Gary W

Stu Jackson · May 23, 2014, 07:26:14 AM

Gary,

http://c34.org/bbs/index.php/topic,7398.msg50479.html#msg50479

Also check the belt alignment discussion, at the bottom of "101 Topics" thread.

The 7390 is the length of the belt. Get a 3/8" GATES belt. You can get them at a Napa Auto Store. If you don't know which one is right for you, I suggest you buy a 7400, 7390 and 7395, find what fits, then return the two and buy a second one that's right as a backup and label it with your spares.

IIRC, the Critical Upgrades also has a link to the belt tensioning tool.

[Added - it doesn't, does now: http://c34.org/bbs/index.php/topic,3667.0.html]

Make sure you have the upgraded bracket, too.

My experience is that you have to drop the alternator to get the belt on, or else the belt will be too long.

What alternator do you have?

lazybone · May 23, 2014, 08:58:27 AM

Buy two.

Ron Hill · May 23, 2014, 09:15:37 AM

Gary : The 39 inch belt (Gates 7390) will fit the stock Motorola alternator. If your alternator is painted bronze you probably have the original alternator.
Otherwise like Stu, said get some longer belts if a PO changed the alternator.

patrice · May 23, 2014, 10:28:13 AM

Hi Gary,

I bougth my belt from CarQuest, go with your belt number, or better bring it with you.
Or any NAPA auto parts will have some, and might be cheaper than the 'marine version' of the same Gate belt you will get at the marine store

garyw · May 24, 2014, 05:21:42 AM

Thanks so much . The members of this group are so helpful. I need to check back to my boat to see the alternator type . Will try the other suggestions that were made here. Gary

Ron Hill · May 24, 2014, 05:39:24 AM

All : If you look at the NAPA belts, it says made for NAPA by Gates!!

patrice · May 26, 2014, 06:34:05 AM

The one I got from Carquest, it's just Gates XXXX stamp on it. a genuine one ;-)

lazybone · May 26, 2014, 12:34:09 PM

"Dayco, Top Cog". Is well respected. But I think it is also made by Gates.

garyw · May 28, 2014, 11:15:46 AM

I found out that my alternator is the balmar 71280 model. I got the belts from napa and will see which one fits.

Gary

Vic Suben · June 30, 2014, 12:59:39 PM

A few years ago I found a belt that the PO had left. The belt was encased in a Gates 7405 sleeve, and lacking any other information about the belt, I installed it. Today I replaced that belt with (you guessed it) at Gates 7405. When I removed the old belt, I realized it was considerably narrower than the new belt. Upon closer examination I notice that the old belt has a NAPA part no. 3VX400. The new belt seems to working very well but I'm not sure which is the correct belt to use. Does anyone know the correct part no. for the alternator belt? My engine is the M25XP.

Thanks,

Vic

Stu Jackson · June 30, 2014, 02:48:20 PM

Vic, my guess is he might have left an old belt in the newer sleeve. You need a 3/8" Gates belt, available from Napa. The 7405 is the length. I have used 7390, 7395 and 7400 lengths, currently using 7395. The 7405 is pretty long and may bottom out your adjusting bracket hole.

http://c34.org/bbs/index.php/topic,7398.msg50479.html#msg50479

Ron Hill · June 30, 2014, 03:07:53 PM

Vic : The 3/8" width belt length all depends on the alternator pulley - that's the variable!!

Look in WiKi and the numerous posts on this topic.

A thought

Vic Suben · June 30, 2014, 03:58:00 PM

Thanks Stu,

I'll pick up a 7395 or its NAPA equivalent.

Vic

KWKloeber · June 30, 2014, 07:50:41 PM

Vic,

Do you have the alternator upgrade bracket, do you have the oem 55 amp alternator? -- that makes a difference on the length.

I am a Westerbeke parts dealer - my distributor recommends the Dayco Top Cog belt. IMHO, it is the best belt you can buy for our applications under our conditions. It is much better than bottom-cog belts (JTSO.)

I switched on Westerbeke's recommendation 10 years ago on my M-25 and will never go back to the other style. The Top Cog runs cooler because there's more belt in contact with the pulleys (heat dissipation), and with more in contact there's less slippage also (so less wear.) The Top Cog for the M25 and XP is 0.44" wide, and that's what the Westerbeke distributor recommended.

I have belt numbers but hesitate to post them because there is apparently some variance in which fits the XP. If you give me your current belt outside circumference, I can tell you which Dayco Top Cog belt matches that length.

You can also do a dimensional look up here. Just enter "close" numbers - it will return a list of options.
http://www.daycoproducts.com/online-catalog-1?part_type=30

and a part interchange look up here... (bottom left box)
http://www.daycoproducts.com/online-catalog

I highly recommend that belt - Advance auto carries Dayco - and others do also I'm sure.

Cheers,
Ken