Replacement alternator for a Yanmar 2GM20F?

[Bob Pullen HC-33 1981]

We are looking for a replica spare alternator for our Yanmar 2GM20F, circa around '95.
It has been painted over and thus we were unable to identify it. Could anyone help us identify the alternator (see pix) and perhaps suggest a delco or similar replacement which would fit the same foot print?
We are novices on the mechanical side, and would like to have it in case it stops working in some of the more remote locations we sail/dive. Something that can be easily replaced or used in testing, by being of the same identical size and shape, thinking swap out here (highest level of our current mechanical skills...but improving!).
We're in the US now visiting for a while and are trying to find one in some autoparts stores which might fit. Any suggestions would be kindly appreciated.
Many thanks for any advice or help.
Bob
S/V Seanorita
Yucatan

 

[Stu Jackson]

Re: replacement alternator for a Yanmar 2GM20F ??

That looks a lot my old Motorola OEM on our boat. Try Leece-Neville. Read this: http://c34.org/bbs/index.php/topic,5686.msg35769.html#msg35769

New belt time, too.

Good luck, it should be an easy replacement.

 

[sailaway78]

Looks like mine

An exact 70amp replacement for the one on my 3GM is from a mid 80's model Nissan Sentra. Easiest way is to take the existing one off, take it to an alt. shop. They will be able to tell you what is an exact fit. I replaced my origional 35amp and kept it for a spare. The 70 amp is a direct bolt on, with the exception the wiring plug needs to be changed. It's pretty easy to do, and the alt. shop can show you exactly how it works. Price for an auto alternator is around 100 bucks for a 70 amp.

 

[Ed Schenck]

Re: replacement alternator for a Yanmar 2GM20F ??

Pretty sure that is an Hitachi alternator Bob. I had an Hitachi 35-amp OEM on my 2QM20. Then I found a 55-amp Hitachi on E-Bay and upgraded. Both looked just like yours.

 

[Maine Sail]

Stock Hitachi alts, during the 1981 vintage on the 2GM's, were either an LR135-74 or LR135-105. Later ones had a LR135-105 both were 35A.

 

[Tricia]

Re: 2GM20F alternator

Mine had a 55 amp Hitachi when I bought the boat.

 

[Bob Pullen HC-33 1981]

Re: 2GM20F alternator

Hey thanks to all for the quick response!
I appreciate the replies.
Tricia: Would you happen to remember what was the model of the 50A Hitachi?
I have a house bank with 6 T-105, in 3 pairs...supposedly 600+ a.h., although I never drain them close to 50%, I still would like to have a bit more on the charging side, if I can find one without needing any mods on the install.
Anyone have suggestions of a preferred distributor?
Thanks again for the help.
Bob

 

[John Nantz]

Six golfcarts?

I have a house bank with 6 T-105, in 3 pairs...supposedly 600+ a.h., although I never drain them close to 50%, I still would like to have a bit more on the charging side, if I can find one without needing any mods on the install.

That may have contributed to why the old one failed. The OEM alternators are not the most robust construction. Perhaps considering a replacement with a design that can handle a lot of heat over time would be good.

For now, replacing in kind would get you up and going again but something like a Balmar with a new multi-step regulator would last longer. One of the problems with alternators is the diodes wear out and using an alternator designed to recharge a tractor start battery to recharge a huge battery bank is a lot different.

Unless there is no way for mixing them up, a picture of how the cables are attached to the existing alternator would be good to make sure they go back on the replacement in the right place would be good. Say, put some masking tape on one of them for easy identification.

It would be interesting to know what size battery cables the bank uses and what the amperage rating is for the selector switch.

 

[Ralph Johnstone]

The Alternator on Our 1999 Vintage .......................

.............. 2GM20F is a Hitachi model LR155-20B, 12 volt, and 55 amp output.

The way they are jammed into that compact space and the shape of the mounting bar, this may limit you to another Hitachi of the same model you currently have.

 

[Bill Roosa]

Re: replacement alternator for a Yanmar 2GM20F ??

Be sure to check for the ground wire terminal. Yours looks to have a dedicated ground terminal (hard to tell from pics) If it has two large (like charging amp large) cables coming off the back the you have a dedicated ground. These are a little harder to come by and if such is the case "MAY" require a rewire of the ground circuit if you cannot find an exact replacement.
Dedicated ground alternators usually are attached to engines that are not grounded with large enough wire to handle charging currents so IF you have one AND can't get a replacement you will want to check the engine ground wire to make sure it is able to handle the current.
FWIW

 

[Tricia]

Hitachi 55A alternator

Whaddaya know, it's sitting right here. Model is LR 155-20. It's bearings were just starting to wear and when I asked an alternator shop about replacing them, they said, "Oh, it'll be OK for a while." Nobody said what a while was. I bought a rebuilt 80A Hitachi for less than $200. The shop changed some wiring inside - can't remember exactly what they did - to make it compatible with the old 55A one. The new alternator fits on the same bracket as the old one, but the bracket now rubs on the insulation of the engine box. and I had to buy a longer belt. Kept the old alt. as a backup. I understand that 80A is about as high as one should go on the 2GM20F.

 

[Bob Pullen HC-33 1981]

Thank you for all the great help!

My current alternator is still working pretty well (ignorance is bliss?). I do have a Trimetric battery monitor that shows me the battery's condition at all times, and it was setup by well experienced professionals, who in this case, did a great job. The battery's were all wired by the same pro's, who used oversize (expensive) cables, and I am very satisfied with the way it was done.
At the time, I was urgently trying to get going, and decided to keep the same alternator. It's 5 yrs later, and the going's been great, so it's time to build up the spare parts dept. and after all this help, I'm considering getting a 50A identical replacement, and keeping this one as a spare (after a mech gives it a dose of prev. maintenance/look over).
Thank you all for the input, suggestions, and great advice.
I will follow up on the wire size checking, and other points that were brought up, as soon as I get back aboard, in another couple weeks.
Once again thanks for such a great resource.
Bob
S/V Seanorita
Yucatan