Yanmar 2QM20 (alternator Recommendation)

[sailnoobee]

Hello, everyone newbee here. just purchsed a sail boat.
i have Yanmar 2QM20 with a balmer 120 amp alternator.
the belt sqeekes randomly and i was informed by previous owner. that the alternator is too strong on the engine and often breaks the belt. i want to change the alternator to maybe a 60-65 amp. i dont know what to look for. any suggestion would be great. i said twice and both time the belt sqeeked for 1-3 min.

[a64pilot]

Do you have an external regulator? If so then the alternator can be derated most likely and that is a much better solution.
If not then installing a Balmar 614 is they way to go, there are others also.

[sailnoobee]

a64pilot,
thank you.
i do have external regulator.

[NYSail]

Yes alt is a bit much for that engine. As was said, derate to match your
Power requirements. Best solution. Will also give a longer life to the alt.

Good luck!

[a64pilot]

Originally Posted by sailnoobee

a64pilot,
thank you.
i do have external regulator.

I expected as much, do you know what type it is?
Does it look like this? If not can you take a picture?

[a64pilot]

I am going to go out on a limb and assume it does, if so read this article a couple of times, program it according to the article, and don’t be shy about derating it further using the belt manager function since it’s the belt that’s the issue.
https://marinehowto.com/programming-...age-regulator/

My opinion is the ideal way to use an alternator is to take a big one, and seriously derate it, that means it will always run cool, and cool running alternators last a long, long time.

[a64pilot]

After you get it programmed correctly try to clean out all the dust, be sure to disassemble the air intake, it may have a fine screen that’s clogged with belt dust.

[partingclouds]

Hi,

Just a FYI 2-cent tidbit here. I have the same engine with the original 55 amp alternator with external regulator. It is sufficient for the needs of all charging requirements.

[motretu]

many years ago [90's] i owned a '78 lancer36 with a 2qm20. i wanted more charging power so installed a balmar 80 and had same problem as you are having. ext. regs then didn't offer belt manager derate profiles. wound up having an aluminum bolt-on crank pulley made for a larger width belt [about $200 then]. worked well. it was a raw water cooled engine, so adding the new pulley only required a small adjustment to the balmar mounting offset. when i sold the boat, removed the balmar and custom pulley, remounted original alt. and belt. sold balmar, still have pulley [which is available].

[sailnoobee]

Originally Posted by partingclouds

Hi,

Just a FYI 2-cent tidbit here. I have the same engine with the original 55 amp alternator with external regulator. It is sufficient for the needs of all charging requirements.

previous owner wanted to keep the ice box running so he installed a 120 amp alternator.i want to change it (where can i or If i even can get a 55 amp alternator) all i can find is the 35 amp alternator. i know balmers would be the next bet. but i dont want to spend 700+

[sailnoobee]

Originally Posted by a64pilot

I expected as much, do you know what type it is?
Does it look like this? If not can you take a picture?

thank you for picture. its same one i have and, its programmed Correctly.

[sailnoobee]

FOUND A ALTERNATOR!!
https://www.amazon.com/ALTERNATOR-YA...6662820&sr=8-3
ITS 35 AMP.