Belt Size

[Roland5048]

Have a Yanmar 3ym20 in my boat. Last Sunday, about 200yds from my slip, the belt to the raw water pump decided to disintegrate. Was able to get to slip before overheating. Going to replace both belts. Have the alternator belt off. Two questions.

1. Does anyone know the size of the raw water pump belt? There was hardly anything left of it. I can't find anything in any manual.

2. Besides going to my Yanmar dealer and paying an outrageous price, can I get a belt at a local dealer like NAPA? If so, what brand would be recommended?

 

[dlochner]

Can't answer the first question, but for the second, yes. Get a Gates, more expensive but Gates has a good reputation for longevity.

Also make sure you tension the belt correctly. See this article: Belts | Steve D'Antonio Marine Consulting

 

[Warren Milberg]

I second the motion about buying Gates belts rather than Yanmar belts. Here is a pic of a Yanmar belt that was in service on my boat for less than 50 hours. I had no burrs or nicks in the blocks/pulleys. It was just poor quality control on the part of whoever makes belts for Yanmar.

 

[jviss]

I would wonder why the belt disintegrated. Is the pump seized, or perhaps partially so?

Agree on the Gates belts, get the highest H handling available in your required size.

 

[Bill Roosa]

are you driving a high output alternator? Common problems are getting the wrong "V" angle belt (there are two), trying to drive too much alternator with too few belts (50 amps is about the limit for a single belt). No belt, no matter how well manufactured will survive being use on the wrong pulley (v angle) or being overloaded.

 

[Roland5048]

Thank you for the quick responses. I guess I could use a small dia. line and wrap around the pulleys to get a circumference. It's just too tight in there to get a tape measure. Maybe a tailor's tape might work. Would I fine Gates belts at NAPA?

 

[jviss]

NAPA generally carries good belts, but may be branded "NAPA," so no good way to trace them back to Gates.

Measuring belts:
http://www.vbelts4less.com/Measuring-Belts_ep_46.html

 

[Roland5048]

Belt more than likely let go because it was almost nine years old and over 600 hours on it. These were the original belts from when this motor was brand new when I had it put in. No lectures please, thank you. I know better.
Pump is not seized. It is fairly new. Will be replacing the impeller also, although fairly new, due to it's running dry for about two minutes.
Alternator is stock that came with motor. 60 amp, I believe.

 

[jviss]

Gotcha, sounds like you just need a belt.

 

[Johnb]

Be aware that metric and imperial size belts have subtle different differences in angle and other dimensions.
http://www.machinedesign.com/mechanical-drives/pitfalls-interchanging-us-and-metric-standard-v-belts

 

[Ken13559]

Its either M19 or M20.

 

[Ron20324]

My 3YM20 came with a 20, but with stretch and age, it was too long to be adjusted tight enough. I put in a 19 and it gives me a proper adjustment travel. About a 2 inch chunk of the inner half of the belt thickness had fallen off. I saw it before it broke.

 

[Bob S]

Recommend keeping a spare on board once you figure out the size.

 

[dlochner]

Recommend keeping a spare on board once you figure out the size.

Cheap insurance.

 

[Roland5048]

Measured out at 20 in. using a cloth tape. NAPA is ordering me a 19 and 20 inch. Can bring back the one that does not fit. Bought an alt. belt from them, also. It's in NAPA packaging but is made by Gates.
A spare will also be ordered.
Hope to up and running by the weekend.
Will post the sizes after all is said and done.
Thanks for all the responses.

 

[Roland5048]

Will be replacing the impeller also, although fairly new, due to it's running dry for about two minutes.

I'm surprised no one caught this gaffe. Just occurred to me.
The impeller did not run dry... it did not run at all due to the belt giving way. Replacing anyway.