Recommended Alternator Belt + Length

[jason3317]

I am in process of upgrading the charging system on a Yanmar 2GM20F. I have a Balmar alternator with the 2.5" diameter pulley. I believe I will need to supply a shorter effective length belt.

What is the recommended length of this new belt, based on experience of others?

Jason

[JohnRPollard]

Hi Jason,

When we added a Balmar alternator to the 2GM20F on our previous boat, I seem to recall that the belt length was the same as it had been previously with the OEM Hitachi alternator. We did, however, need to upgrade to a heavy duty belt in order to withstand the new load/drag of the higher amp alternator. We went with a proper length "Gates Green Stripe" belt.

[Valiente]

No clue as to the length...use a string and measure the string or measure the old belt.

But I second the Gates Green Line make...they are recommended by others besides me as being tougher and more reliable than most.

But nothing beats having the proper tension. On most 35-100 amp alternators on 30-80 HP diesels, this means tight enough so that an average person's thumb can deflect the tightened belt about the thickness of a dime or two, i.e. not rigid, but still pretty snug.

This can be tricky to achieve solo, but leaning gently against a pry bar while you tighten the armature mount bolt usualy works for me.

[jason3317]

Thanks for the feedback. I agree on using the Gates HD series belts; I picked up a stock length (37") and, also, a one inch shorter belt in case the smaller pulley needs it.

Jason