Alternator Belt Tension R25

[Metric Rider]

Looking for any tips on changing and tensioning the belt on a Yanmar 4JH4-HTE 110 hp in my 2008 R25. The operation manual does not have a lot of detailed info. Not sure what I can get leverage on and not break anything!

 

[j&lgray]

It has a been over a year since I had the Laurie Ann, the same year as yours. Some models had one belt, others had two belts. Mine was a single belt, I believe the belt tension is controlled by the bolt that tightens the alternator. Loosen it, the alternator swings toward the block and remove the belt. Put on the new belt and expect barely enough clearance to do it, swing out the alternator, tighten the bolt just a tad, and then use a handle or rod to lever out the alternator a bit more. The belt should deflect about a 1/4." More, and the belt will be loose and squeal. To tight, and the belt will wear out more quickly (sign is belt dust in the engine compartment) or will affect the alternator's bearing.

Great question. The job is do-able and straight forward. Hope this is helpful.

 

[Metric Rider]

Thanks for the quick and great response. A couple of followup questions:
Do you need to normally loosen the bottom bolt on the alternator to allow it to move (this is in addition to the top nut allowing the lateral adjustment)
Also any specific tips on how to apply leverage on the alternator without breaking something

 

[j&lgray]

Typically, the bolt that the alternator pivots on does not need to be loosened. As to how to tighten the belt, there are several ways. Try NOT to use a hammer and tap the casing of the alternator for those self-evident reasons. I have used the handle of a hammer, a breaker bar and a pry bar has a lever that is placed between the alternator and block being careful to push on something fragile. Also, I have used a hammer to tap on flange that the tightening bolt runs through; tighten the bolt just beyond snug, not tight, and tap on the flange. The belt will often stay tight enough and long enough to tighten the bolt down.

Hope this is helpful. Sorry for the delayed response, Andiamo is on the Jersey Shore waiting out the affects of the distant Hurricane Arthur as it spins toward Cape Cod from the Carolinas.

 

[Metric Rider]

Thanks so much, just the info I was looking for! Arthur is coming through our area (Bay of Fundy / Saint John River valley) at this moment.

 

[briandrew]

I faced a similar problem when I wanted to change the impellor. My local mechanic suggested to get at the impellor I had to cut the belt off and once the impellor was replaced I would put a new belt on. This seemed rather wasteful and after making a few enquiries I found a mechanic who told me about a belt remover/replacer that will save your old belt so it can be replaced. In your circumstance it sounds like you simply want to replace the old belt with a new one and providing the tension was right before why change anything, simply replace the old one with the new. I bought this tool and it has proved to be a godsend since I had seized bolts and ended up taking the belt on and off 3 times before finishing the job properly (a long story made short). Unfortunately I left the belt remover/replacer on the boat so I can't reference the packaging but I can tell you I bought it from NAPA (auto store in Victoria) and on the invoice they called it "Stretch Belt Mate Kit" and their part number is 70990 (probably just used by Napa stores), the cost was $46.29 Can. It is easy to use and I highly recommend this for all boat owners wanting to remove or replace belts. Good luck with it. Andrew

 

[Brian B]

I faced a similar problem when I wanted to change the impellor. My local mechanic suggested to get at the impellor I had to cut the belt off and once the impellor was replaced I would put a new belt on. This seemed rather wasteful and after making a few enquiries I found a mechanic who told me about a belt remover/replacer that will save your old belt so it can be replaced. In your circumstance it sounds like you simply want to replace the old belt with a new one and providing the tension was right before why change anything, simply replace the old one with the new. I bought this tool and it has proved to be a godsend since I had seized bolts and ended up taking the belt on and off 3 times before finishing the job properly (a long story made short). Unfortunately I left the belt remover/replacer on the boat so I can't reference the packaging but I can tell you I bought it from NAPA (auto store in Victoria) and on the invoice they called it "Stretch Belt Mate Kit" and their part number is 70990 (probably just used by Napa stores), the cost was $46.29 Can. It is easy to use and I highly recommend this for all boat owners wanting to remove or replace belts. Good luck with it. Andrew

I found a video showing how to use this special tool. https://m.youtube.com/watch?v=uGJCtWKkaTE
Having removed the belt to change the raw water impeller I can see how useful this can be. It will also prevent damaging the pulley.
Thanks for posting the info, one more tool I will have to buy.