Re: Source for shaft alternator

Eric Freedman


The reinstallation of a shaft generator seems like a simple project.

You would need to know the speed of the shaft when cruising. Once you have that information, I would go to a shop that rebuilds alternators and ask what speed you would need at the alternator to produce electric.  You can then figure out how large the pulleys you will have to fabricate make the alternator run at the desired speed.

I would think you could get an alternator that outputs between 50 and 80 amps. You would also have to know if your boat has an isolated bonding system and if you need 24 or 12 volts for your primary bank.

Then it is just a matter of fabricating a mount for the alternator and an adjustable arm to tension the belt, as well as making a circuit to energize the alternator on initial startup.


Attached please find a photo of a C drive Yanmar with a shaft generator and a serpentine belt.

The alternator in the photo seems to have a very big pully mounted to the shaft since it is after the transmission.

Fair Winds


Kimberlite Amel Super Maramu #376




From: On Behalf Of marklesparkle59
Sent: Sunday, August 08, 2021 3:38 PM
Subject: Re: [AmelYachtOwners] Source for shaft alternator


Lance this is a photo of my Shaft generator, from 1983. I have not got anything out of it yet and will soend some time tomorrow checking the connections. I also have a switch inside the cabin. If I can provide any info please ask.

Mark Porter

Sea Hobo

Sharki #96


On Sun, 8 Aug 2021, 16:07 Patrick McAneny via, <> wrote:

Lance, I have SM and the shaft alt. disconnected , I have been thinking of removing the pulley and replace it with a spacer. I have a Volvo TMD22a . I don't know if they are  interchangeable ,if so I would be interest to trade. The problem for me is to find the time to move the engine ,etc. You could research if they would swap out ,without  modifications.



SM Shenanigans 

Sassafras River, Md.

-----Original Message-----
From: Lance Leonard <Elscubano@...>
Sent: Sun, Aug 8, 2021 10:58 am
Subject: [AmelYachtOwners] Source for shaft alternator

I am looking at ways of increasing my power generating ability on my Maramu. Currently we have two 80w solar panels on the dodger and an ancient Hamilton Ferris wind generator on the mizzen. We keep our dingy on the cabin top above the aft berth which seems to be the only other place permanently attach soar panels. We thought about installing some on “wings” off the lifelines, but our paddle board and the boarding ladder wold make that a little challenging. Hence the shaft generator, Minerva was originally equipped with a shaft generator that has been removed at some point, there is a spacer on the shaft at the output of the transmission which is where the pulley lived originally I think. I haven’t tried to reach out to Amel yet since they went to the “C” drive I can’t imagine that that would be something they kept around. I think I might be able to have a machine shop fabricate a pulley to fit the where the spacer is now but I would think it would have to be a particularly low speed cut in alternator to get any meaningful output. Any thought or advice would be appreciated.
Lance Leonard
S/V Minerva
Maramu #135

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