Is the engine belt tight enough? - SailNet Community
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post #1 of 21 Old 05-18-2008 Thread Starter
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Is the engine belt tight enough?

To usher in the new age of remote diagnostics, here is a video of my engine running. Does it look like the engine belt is too loose? Is this wobbling of the belt normal?
Engine running
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post #2 of 21 Old 05-19-2008
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It could be a little tighter. It should not ride up and down in the pulley grove after about 60 seconds of running.
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post #3 of 21 Old 05-19-2008
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Could be...

It could be a combination of alignment and it being a little loose.. It should not ride up and down like that. Perhaps there is a rust spot on the pulley??

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post #4 of 21 Old 05-19-2008 Thread Starter
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Quote:
Originally Posted by halekai36 View Post
It could be a combination of alignment and it being a little loose.. It should not ride up and down like that. Perhaps there is a rust spot on the pulley??

Certainly a possibility. I spray the engine with Boeshield occasionally but it still tends to get surface rust - not sure why, there is no direct water ingress (though engine compartment certainly isn't humidity proof).

I tightened the belt a bit, will also clean the pulley again.

How can alignment be verified/adjusted?
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post #5 of 21 Old 05-19-2008 Thread Starter
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BTW, I start to think I may be a closet powerboater (oh humanity!). The sight and sound of working diesel just makes me feel warm and fuzzy for reasons I cannot fully explain.
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post #6 of 21 Old 05-19-2008
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I didn't see how it was riding up and down. The idea of posting a video for opinions etc is a great one though - I'll keep that one in mind.

It sounded good and the belt looked fine to me, but don't count on my opinion for much. I always tell my wife "if something happens to you my next wife is going to be a diesel mechanic."

Twenty years from now you will be more disappointed by the things y%^&*.....oh never mind. 90% of the people on sailing forums already use that as their signature! I'm not a conformist.
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post #7 of 21 Old 05-19-2008
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Originally Posted by brak View Post

How can alignment be verified/adjusted?

If one of the fixed pulleys, not the alternator, has a flat side to it use a c-clamp to mount a straight edge to. Align the straight edge to run parallel with the belt. Then measure the gap between the straight edge and belt, as it leaves the pulley you have the straight edge clamped to, and then measure this gap where it enters the next pulley. Use a set of calipers it will make measuring the gap easier..

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Last edited by Maine Sail; 05-19-2008 at 02:05 PM.
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post #8 of 21 Old 05-19-2008
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Just be sure you don't over tighten the belt as that will quickly ruin the alternator bearing. The same goes for the raw water pump. My Yanmar owners manual specifies a deflection of 10mm (that's .40 " or almost half an inch) The measurement is taken in the middle of the longest section of the belt using your finger to push inwards with moderate force. Again, it's better to err on the loose side. Same principle as wheel bearings on a trailer.

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with all possible kudo's to Hal for millimeter measurements, Nicks point is more precise, belt deflection per your owners manual is more correct. Yanmar has a plethora of manuals out there, aftermarket included. Some wobble is intended and desired. It doesn't have to be precise, just stay on the pulley and be consistent.
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post #10 of 21 Old 05-19-2008
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Quote:
Originally Posted by chucklesR View Post
with all possible kudo's to Hal for millimeter measurements, Nicks point is more precise, belt deflection per your owners manual is more correct. Yanmar has a plethora of manuals out there, aftermarket included. Some wobble is intended and desired. It doesn't have to be precise, just stay on the pulley and be consistent.

The mm measurement is for proper belt alignment NOT tension.. Tension is easy, proper alignment can be a PITA especially if you've changed to an after market alternator....

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