EXACT replacement for Motorola 55 amp alternator?

Can you have yours rebuilt to that spec?

I'm not sure if it could take the load on a rebuild plus I wanted to use it as a backup.

If you can't afford the Balmar alternater, you will not get anything comparable in that style. A lot of alternaters are only rated for a maximum output & that rate falls off quite quickly once things start to warm up.

meridian said:

Is there an exact replacement for a 55 amp Motorola alternator that puts out close to 100 amps? I want to keep the old one as a backup. I’m not looking to pay $600+ for a Balmar, etc.

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Short answer is yes there is. Balmar uses the same frame. I found a rebuilder on Vancouver Island who has this as an option in his catalog. Ask around the waterfront.
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JC Whitnet sells a kit to up the output to about 80A.

This is a so so fix as the cooling setup is not improved , so full output long term at high temperature is a dream.

Some alts have a "universal" fan which can be upgraded to a better design that is for the direction your alt spins.

For a long time (perhaps even now) the Ballmar units were simply Les Tech rewounds with "better output " guts, and nice paint..

The only real way to have a higher output is a better alt, usually a 135A truck unit for about $150.

IF the guy at the local parts store is willing you can find better alts , the same size as the 55 , which is built for bigger cars , Caddy or big Olds.

He can get down the Caddy box for the right year (OLD IS BEST) and see which are identical.

Old is best because the older units have external regulators , so switching to a Marine 3 or 4 stage unit will be a snap.

The stock built in auto/truck charge regulator is almost useless for charging house batteries

FF

If you have a 120 that uses a gm style alt . I found a large frame 100 amp unit on ebay for $50 bucks, worked great just needed a longer belt

You probably will need to unsize your wiring

I just put three Delco factory rebuild units on my Lehmans to replace the original 55A Motorolas. One is a 70A unit ($80 new unit not rebuilt) the other two are 108A ($105). I had an alternator shop add tach sends for $6 each. I have a couple of hundred hours on them so far and they are incredible! I put smaller 2 3/4", I think, pulleys on as well given our 1400rpm cruise. Used to show 12.2V cruising now it's 14.4V with lots of 110V stuff running off our 3100W inverter. Bought them at Napa Auto Parts but really any shop will have the same things. The second alt on one engine meant buying a bracket from American Diesel ($180) and a universal alt tension bracket from Napa ($15).

It has been one of the most gratifying things I have done to the Lehmans.

I put smaller 2 3/4",

This will require a higher initial tension , and care that the belt NEVER slips.