2gm20F Fan Belts

rjc9136quinn · #1 10-02-2009

Good morning,
I have a Yanmar 2gm20 F with just under 300 hours. My fan belt is fraying into a fine ,fluffy powder. I lost a belt in Vineyard Sound in August and the replacement is fraying in the same manner. I have tried tightening and loosening, both to no avail. Pulleys appear to be in line and no play in the sheaves.
I'm running out of ideas to try for what seems to be a rather simple problem.
If anyone else has had a similar problem and solved it I would love to read the solution.
Thanks.

rjc9136quinn

Vasco · #2 10-02-2009

Usually it's an alignment problem but if that's ok I'd switch to a better grade belt. I use Dayco Top cogs.

badsanta · #3 10-02-2009

I had a yanmar 3gm30 and found my alternator was not aligned right. I had a machine shop re drill a hole ($10) and put in a larger bolt. It used to twist as you tightened it down, now rock solid.

timebandit · #4 10-02-2009

So--What are you driving with that belt?

timebandit · #5 10-03-2009

A little something worth reading--

Notes on Pulleys and Belts

JohnRPollard · #6 10-03-2009

Quote:

Originally Posted by rjc9136quinn

Good morning,
I have a Yanmar 2gm20 F with just under 300 hours. My fan belt is fraying into a fine ,fluffy powder. I lost a belt in Vineyard Sound in August and the replacement is fraying in the same manner. I have tried tightening and loosening, both to no avail. Pulleys appear to be in line and no play in the sheaves.
I'm running out of ideas to try for what seems to be a rather simple problem.
If anyone else has had a similar problem and solved it I would love to read the solution.
Thanks.

rjc9136quinn

Fan belt?

I assume you mean the alternator belt?

Are you running a stock Hitachi alternator, or have you upgraded to a high-output alternator?

If you're running a high-output alternator, the stock belts just aren't up to the loads and tend to wear quickly. You normally need to use a special heavy duty belt like a Gates Green Stripe.

If it's just the stock alternator, have you had any indication that the bearings in the alternator are binding up? Noise, resistance, lower output, etc?

roline · #7 10-03-2009

The 9.2 Cal that I bought with a 2GM20 had black dust all over the front of the engine. I spent a couple hrs cleaning the engine and compartment and then replaced the alternator belt with a top cog belt from the local car parts store. 55 amp alt...It has worked well, no new black dust, for over 5yrs. The old belt had worn thin and was slipping in the pullies. The small raw water pump belt did not have an equivilent, so I had to order a Yanmar belt.

Stillraining · #8 10-03-2009

I second the Gates Green strips..I once had one flip over backwards due to misaligned pulleys and run that way for a while..It was badly deformed when i caught it and took it off..I could barley twist it straight with my hands but it would not keep its shape...just for grins I put it back on and within a couple hours it was running true and straight..Tough Belts indeed...I took it off and kept it as a spare. ..Also check your pulleys for bad rust in the groove.

RichH · #9 10-03-2009

Yanmar sheeves are prone to rust !!!!!!! Check the pulley on the engine fresh water pump - notorious for rusting and leaving a roughened surface where the belt contacts the sheeve. Very common problem on QM and GM Yanmars. Also check the surface condition of the alternator sheeve belt. You can remove these and 'dress' them back to smooth if you have a lathe, etc.; but, its usually cheaper just to replace them.

A good idea when storing the boat long term is to spray on 'Boeshield' on the shiney surfaces of the sheeves ... to prevent rust and pitting.

The second problem may be your alternator (load). If the alternator is working against a FULL load you may be exceeding the belts ability to transfer torque to the sheeves. If the the sheeves are smooth and aligned and you are getting 'dusting' than its time to consider to 'derate'/decrease the alternator output - easy to do with an external 'smart' regulator. An external 'smart' regulator will bring the alternator slowly on line (prevent excessive belt 'dusting', instead of 'hitting it' with a full load from the start.

First off - look at the condition of the wear faces on your sheeves; especially the steel sheeve/pulley thats on the FRESH water pump.

rjc9136quinn · #10 10-08-2009

Quote:

Originally Posted by rjc9136quinn

Good morning,
I have a Yanmar 2gm20 F with just under 300 hours. My fan belt is fraying into a fine ,fluffy powder. I lost a belt in Vineyard Sound in August and the replacement is fraying in the same manner. I have tried tightening and loosening, both to no avail. Pulleys appear to be in line and no play in the sheaves.
I'm running out of ideas to try for what seems to be a rather simple problem.
If anyone else has had a similar problem and solved it I would love to read the solution.
Thanks.

rjc9136quinn

Thanks to all who responded to this inquiry. I am going to be trying several of the suggestions and will post my results when I have them.
rjc