Alternator Belt Tension

[Mark Thurlow]

I have a monohull with a YANMAR 3jH4 HTE. In addition to a std Engine Alternator it has a Balmar 185 Alt with external Reg. It has worked well for many years, now feeding my 5year old LiFePO4 Bty system.

The Serpantine Belt tension is controlled by a bolt tensioner that is a pig to adjust in the very tight space. Now, I am not able to adjust the tension using the bolt as I have done before - loosening one side and tightening the other.

Maybe the threads are stripped or something has come apart; I cannot tell but the Alt is still fixed in place.

Looking for advice on fitting an alternative tensioning system, a curved bar will not fit. Can I fit a separate tensioner and ignore the bolt tensioner. If yes any make/model suggestions?

And any insight as to what has gone wrong with the bolt system

[GreenWave]

So you have loosened both bolts and the Alternator wont move? If so sounds like some corrosion may have set in. Clean it up light tap with hammer on the bolt maybe?

[Mark Thurlow]

Thanks but it NOT the standard bolts I am trying to address but the threaded bolt system used to control the belt tension.

It is a sort of worm drive arrangement.

[GreenWave]

ahhh gotcha. I have searched endlessly for the ideal tensioner solution and have regressed to the 2x4 to get leverage.

[hlev00]

Maybe cut out and replace the existing tensioner but put it on your annual maintenance list to loosen and lube. Also serpentine belts don't have to quite as tight as V belts though with a 185A alternator feeding LiFePO4 batteries you certainly need more tension than I require on my 100A charging FLA batteries.

[Bowdrie]

If you can post a picture, we might get a better understanding of the mounting and tensioning scheme.

[skipperpete]

Good luck with the tensioner, perhaps consider an automatic tensioner if space allows such a luxury.

[Mark Thurlow]

The only photo I could show you is the end of a rod surrounded by a nut however:

File drawing attached

Thank you for taking the time.

Mark

[Mark Thurlow]

Originally Posted by skipperpete

Good luck with the tensioner, perhaps consider an automatic tensioner if space allows such a luxury.

That is what I believe I have to do, any recommendations?

Mark

[Bowdrie]

As the alternator swings thru an arc to adjust it, the threaded bar must be able to pivot vertically to align itself.
It appears from the drawing that adjustment is made not by turning the threaded bar, but by alternately moving the nuts in/out on the bar?
Also, if that big alternator is being driven off of a pulley on the front of the water pump I would be very careful to not over tension the belt.
Water pumps, with only one internal bearing do not take kindly to very much side loading out at the front end.
That "angle part" must also be able to pivot on the alternator.
You may just have everything "bound up" with the various bolts.

[skipperpete]

Originally Posted by Mark Thurlow

That is what I believe I have to do, any recommendations?



Mark

There are lots of off the shelf ones available, I like the cummins 5.9 tensioner. The one on the volvo D3-110 seems to work quite well but in the end, its what you have enough space to sensibly fit one into. Go for more wrap rather than higher tension if that’s possible. If you want to temporarily jury rig your existing adjuster it might be possible to fit new nuts and a spacer to move away from the stripped thread section.