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Almost Free parts and serpentine belt conversion

Posted: Sat Aug 22, 2020 1:49 pm
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

Re: Almost Free parts and serpentine belt conversion

Posted: Sun Aug 23, 2020 12:55 pm
by Tricia
Mike, what kind of alternator did you replace the original with?

Tricia
F30 "Muse II"
Victoria, BC

Re: Almost Free parts and serpentine belt conversion

Posted: Tue Aug 25, 2020 8:57 pm
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.

Re: Almost Free parts and serpentine belt conversion

Posted: Fri Apr 02, 2021 5:24 pm
by mike cunningham
Quick update on n my hot alternator situation.

I was unable to resolve the heating issue. It was a bit difficult to troubleshoot because it would heat up and basically turn itself off as a protective measure. I assumed there was something external to the alt causing the problem. I could not observe it's charging performance for long because it would heat up shut down the field current and not charge which is what it is supposed to do when hot.

Anyway, other fish to fry so I just put it on the back burner. I did determine my alt temp sensor was bad so bought a new one. While replacing the sensor with engine off of course I noted some sparking between the stator output lug and the grounded case bolt I was attching the sensor to.

That shouldn't happen I says!

Did some TS (which I should have done months ago) and realized there was a shorted diode in the rectifier.

Thought about a rebuild but the balmar alt had more than 1000 hours on it, had heated up many times, and Compass Marine had a replacement 120 amp alternator which will serve well when I upgrade to lithium batteries at some point. Also the cost was very reasonable. Not a huge add to what a rebuild would have been.

Rod at Compass Marine has been very helpful and many of you are probably familiar with his excellent "marine how to" site which I wanted to support, so all good.