Almost Free parts and serpentine belt conversion

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system
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mike cunningham
Posts: 355
Joined: Sat Dec 20, 2008 11:21 am
Location: Jacqueline, F30 #3, Discovery Bay, California

Almost Free parts and serpentine belt conversion

Post by mike cunningham »

All,

I modded my 2GM20F to a serpentine belt for crank, fresh water pump and alternator. I have the original alternator and fresh water pulleys and at least one if not two brand new Yanmar OEM belts. I will give them away for free but recipient will have to pay the UPS which would probably be somewhere around 8 bucks. I will drop them packed up at my local UPS store if anyone is interested.

Regarding the mod itself, it was really easy, hardest part was replacing pulley on alternator but a pal's impact wrench made quick work of that. The rationale was to reduce belt dusting which I could never overcome and to simplify belt tensioning with the supplied newfangled alternator bracket which has a really cool tensioning adjustment. It was not cheap but gives me a lot more confidence in reliable belt tension and performance.

Both Balmar and Electromax sell the serpentine kits (maybe others) and check out the "belt buddy" bracket at Balmar. That can be purchased as a mod to either belt system and is really a game changer with respect to belt tensioning.

Finally, I purchased a tension tester on Amazon. This thing is also super easy to use and appears to provide pretty accurate tension measurements.

https://www.amazon.com/gp/product/B000M ... UTF8&psc=1
Mike Cunningham
Freedom 30 (Mull) Hull #3
Build date...June, 1986 . Freedom Yachts USA, sloop, shoal keel
Gun Mount and pole retrofitted (purchased from a Hoyt Freedom 32)
Yanmar 2gm20F , 1600 hrs fixed two blade prop
e-rud and ocean racing equipment

Tricia
Posts: 96
Joined: Fri Dec 05, 2008 9:59 pm

Re: Almost Free parts and serpentine belt conversion

Post by Tricia »

Mike, what kind of alternator did you replace the original with?

Tricia
F30 "Muse II"
Victoria, BC

User avatar
mike cunningham
Posts: 355
Joined: Sat Dec 20, 2008 11:21 am
Location: Jacqueline, F30 #3, Discovery Bay, California

Re: Almost Free parts and serpentine belt conversion

Post by mike cunningham »

Tricia,

I installed a balmar 70A alternator ( for Yanmar 2GM20F mount - exact PNs can be found at Balmar site, there are several mounting options for different engines... https://balmar.net/6-series-alternators/) and an ARS5 regulator, however I did this replacement about 13 years ago. I just upgraded with the serpentine kit to eliminate belt dusting which I was never able to get rid of regardless the tension adjustment. This latest mod resulted in the excess parts I am offering. I have been very happy with this system....but

The other reason for the belt upgrade was to eliminate one source of alternator heating, however this did not resolve the issue and I still get alternator overheat alarms, the super hot weather down here has not helped the situation and has really highlighted a problem I have had for a long time. I believe I will now have to go to a vent of some sort in the companionway steps assembly which covers the engine. The engine consumes a remarkable amount of air so my hope is that if I mount a vent in just the right spot I can more effectively cool the alternator by using the engine air intake as sort of a negative pressure generator inside the engine box which will effectively pull relatively cool combustion air in through the new vent and across the alternator body. I may also install a little door on the vent so I can close it and improve sound damping during cool weather.

This leads me to the biggest issue with the larger alternator in the tight engine space in an F30. It gets HOT in there when the batteries are in bulk charge and the engine is at 2800 RPM cruise temperature. I do have what is called a "small engine" switch installed. This basically shorts the regulator terminals for the overheat alarm and makes the regulator reduce field output by 50% just like it does when it sees the actual alarm. This causes the regulator to drop the alternator down to a couple amps max output and also provides a bit more power availability to the shaft/prop which, really, is the point of the switch. It isn't supposed to be used routinely for temperature reduction or control. The alternator cools off but does not do a particularly good job of charging batteries in small engine mode. So I am planning on installing the vent as my next step.
Mike Cunningham
Freedom 30 (Mull) Hull #3
Build date...June, 1986 . Freedom Yachts USA, sloop, shoal keel
Gun Mount and pole retrofitted (purchased from a Hoyt Freedom 32)
Yanmar 2gm20F , 1600 hrs fixed two blade prop
e-rud and ocean racing equipment

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