I personally would tend to go with an 'inspect and replace' routine rather than go by hours. I check mine whenever I'm checking the oil. I had one break and became much more attentive after that. Last time I replaced it was when I found that the belt was cracking and that some of the rubber 'teeth' on the inside surface had vanished. I have an aftermarket alternator, 80 or 90 amps, and I'm sure it's harder on the belt than the stock alternator, but I still think a regular inspection is in order, since losing the belt can have serious consequences.

I actually heard mine snap; it made a fairly loud bang. I looked at the instrument panel and saw the tach at 0 and investigated. 10 minutes to replace it. Believe it or not, it was NOT night time, in the middle of the channel, with a ship bearing down in dense fog :eek:. The usual time for it to happen :D. Guess that was my once in a lifetime warning.

Come to think of it, I haven't checked it yet this spring; thanks for the reminder.

Gary -
Thanks for the hint on the belt inspection. I was wondering about that myself. If it took 10 minutes - did you have to pull the water hose out?

Also - the belt seems to vibrate so terribly below 2000 RPM. Is that what yours does? I had considered adding a spring loaded pulley between the alternator pulley and the crank shaft pulley to stop that vibration. Is that a good idea? I have M35B engine.

I have found that the NAPA/Gates V-belts with the cogs on the inside will not live very long. I broke one on the last boat in about 25 hours and on this boat at 15 hours a brand new one of them was coming apart and ready to break.

On the other hand, the Dayco TopCog belts that have the cogs on the outside, which are what the OEM Universal belts appear to be, will last a full season (which is about 75-100 engine hours up here) and still have life in them.

My speculation is that the inside cogs reduce the surface area of the belt enough that it can't pull the high loads from 90 amp alternators. Also the smooth outside of the belt gives very little cooling effect. The TopCog belt suffers from neither of these problems.

Haro, if your belt is vibrating I would suggest it is not tight enough. I have a little "cricket" device from Gates that tells me how tight the belt is in pounds. To get even 50 lbs of tension, which according to Gates is the low end, you need to be using a stout bar on the alternator to get it tight. There will always be a bit of vibration but it shouldn't be much.

I hate these crappy old v belt systems. If I could find a kit to convert to a modern serpentine belt I'd buy it in a second. There's a company up here that makes them but not for our engines, mostly only Yanmars.

[QUOTE=baysailor2000;8809]Gary -
Thanks for the hint on the belt inspection. I was wondering about that myself. If it took 10 minutes - did you have to pull the water hose out?
[/QUOTE]

I have an M35A. The water hose does not interfere with the belt, eg., the belt is entirely in front of the hoses. So replacement is fairly easy. I've also modified my engine cover so that it has an opening lid on the top and front, so engine access is a lot easier.

bstreet - when I installed my Ample Power alternator and charging system, they recommended those Dayco belts. Guess I'll have to measure up my spare belt and order a couple.

Gary, the Dayco number is 15400, actually they also make a 15405 and 15410, the 400 numbers are the lengths. On our M35A, the 15400 is a very tight fit but it will go on. The others will also work, they are easier to get on but once broken in the 410 is marginal for getting it tight enough.

Are there pics of your modified engine cover on the site somewhere? If not could you post a couple? Dealing with the standard engine cover is one of the few things that is a genuine pain with this boat.

John, two years is a good time if you're checking regularly, like running your engine with the cover off to listen and watch for "issues." I run our belts anywhere from two to four years. Just changed to a Goodyear, and also have a Gates backup belt. Ours is an M25 engine with a 100A Blue Circle alternator.

You may also be interested in this:

CAREFUL ENGINE INSPECTION

see: [url]http://c34.org/bbs/index.php/topic,5127.0.html[/url]

We have a Critical Upgrades topic on our Message Board as a sticky, much of it related to engine issues. [url]http://c34.org/bbs/index.php/topic,5078.0.html[/url]

[QUOTE=bstreet;8813]
Are there pics of your modified engine cover on the site somewhere? If not could you post a couple? Dealing with the standard engine cover is one of the few things that is a genuine pain with this boat.[/QUOTE]

Thanks for the part #'s, will save me some measuring :)

I did post some pics here ---> [url]http://www.c36ia.com/forums/showthread.php?t=562[/url]

I'm going to try to take some measurements and maybe put together an article about it. Problem is, I did it several years ago, and took no pics at the time. Will see what I can come up with. Must say that it makes many of those routine engine maintenance tasks much easier, so I'm more likely to actually do them.

I check the belt regularly for wear/tension and have had four years out of the Universal stock belt with standard Alternator. I finally changed it after four years just on principal. It showed some wear but nothing that would give me cause for alarm or would suggest imminent failure.

I changed my original belt three years ago even though it still looked good. I average about 60 hours a season. All the engine components are original and standard for the 35A engine. I do, however, check the belt and tightness periodically.