Balmar Alt-mount on 3GM30f - belt too long?

[Richard Kollmann]

Your problem is belt contact on that engine and alternator is less than 140 degrees on alternator pulley. Increasing belt tension will over stress water pump and still slip. I tried a belt spring pensioner that did not work and finally adjusted voltage regulator to 60 amp bulk max load.
The Balmar alternator at 60 amps is still a major improvement over the Yanmar 60 amp because of the far greater output at the same engine speeds.

[phantomracer]

Originally Posted by Richard Kollmann

Your problem is belt contact on that engine and alternator is less than 140 degrees on alternator pulley. Increasing belt tension will over stress water pump and still slip. I tried a belt spring pensioner that did not work and finally adjusted voltage regulator to 60 amp bulk max load.
The Balmar alternator at 60 amps is still a major improvement over the Yanmar 60 amp because of the far greater output at the same engine speeds.

agree. im at the end of the adjustment arm and the belt is just too loose. I always error on the too loose side than the too tight side. but I can easily spin the pulleys now. so i got to do something. It IS a lot better than the v-belt, but still want to get it right.

[Richard Kollmann]

The best performance for a belt drive is when belt covers 180 degrees of pulley your installation is around 1/2 that distance. On my first 3gm30d saltwater cooled engine the alternator belt drove only the alternator. There was a second belt for water pump. When I replaced the engine with the new fresh water antifreeze engine like yours belt contact was as you say not enough to prevent slippage. The Yanmar engineer did not design for a high output alternator with smart voltage regulator. The design 60 amp alternator almost never drew full 60 amps, it was more like 25 amps.

You can reduce alternator output and replace belt with an industrial belt from NAPA this seem to be the best solution.

[deluxe68]

Originally Posted by Richard Kollmann

The best performance for a belt drive is when belt covers 180 degrees of pulley your installation is around 1/2 that distance. On my first 3gm30d saltwater cooled engine the alternator belt drove only the alternator. There was a second belt for water pump. When I replaced the engine with the new fresh water antifreeze engine like yours belt contact was as you say not enough to prevent slippage. The Yanmar engineer did not design for a high output alternator with smart voltage regulator. The design 60 amp alternator almost never drew full 60 amps, it was more like 25 amps.

You can reduce alternator output and replace belt with an industrial belt from NAPA this seem to be the best solution.

180 degrees of contact is only possible when using just two opposing pulleys and they are both the same size. Is this common on sailboat engines?

[Richard Kollmann]

Originally Posted by deluxe68

180 degrees of contact is only possible when using just two opposing pulleys and they are both the same size. Is this common on sailboat engines?

Reciprocating engine belt driven alternators are almost always driven by a much larger crankshaft pulley. In this case the major lack of belt to alternator pulley contact is caused by location of water pump that is driven by the same belt as alternator.
My point was any real torque on a belt with only 90 to 100 degrees pulley contact is going to slip. On this 30 HP engine with its pulley belt arrangement excessive belt tension can damage water pump and even cause rear engine oil seal to eventually leak.

[Maine Sail]

Next belt size down...

The 10 groove J-Series belts Balmar used to use were Jason Industrial belts. For example if you had a 360J10 that would be a 36" X 10 rib belt. You would order one size down...

I have J10 belts out there pushing well over 200A alternators, into LiFePO4 with marginal wrap and zero dust. These are not your fathers antique v-belts....

[phantomracer]

Originally Posted by Maine Sail

Next belt size down...

The 10 groove J-Series belts Balmar used to use were Jason Industrial belts. For example if you had a 360J10 that would be a 36" X 10 rib belt. You would order one size down...

I have J10 belts out there pushing well over 200A alternators, into LiFePO4 with marginal wrap and zero dust. These are not your fathers antique v-belts....

Thanks!

I will try and install the Belt Buddy backwards to get some extra travel for one belt size down, or maybe see what the minimum is to keep the BB installed as designed

There was shockingly less dust with this alt-belt kit than with the v-belt. It was fine when i first installed it, but the belt must have stretched a hair creating the additional deflection.

shorter belt it is

[deluxe68]

Originally Posted by phantomracer

Thanks!

I will try and install the Belt Buddy backwards to get some extra travel for one belt size down, or maybe see what the minimum is to keep the BB installed as designed

There was shockingly less dust with this alt-belt kit than with the v-belt. It was fine when i first installed it, but the belt must have stretched a hair creating the additional deflection.

shorter belt it is

You also need a belt tension gauge, only costs about $20. It is the right way to determine the correct tension.

https://www.amazon.com/Gates-7401-00...+tension+gauge