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Old 01-12-2015, 07:03   #1
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does 2gm gearbox fit 2gm20 engine?

Hey guys, my old trusted Yanmar has failed me and with a head that has a hole in it and blown rings recondition isnt an option.\
I have decided to replace it with a second hand 2gm20 I have found in good condition.
now the question is does the gearbox from the 2gm fit the 2gm20 ?? can I fit the bell housing to the new engine and mount the old box??

I don't mean to sound rude but that is the question.

I don't really want to discuss why I don't rebuild my engine or weather it is my fault that the engine blew up, or if I preheat the engine or if I motor sail, or if I leave the engine in gear when the engine is off etc etc etc. As I feel these conversations sometimes take so many turns away from the subject.
If you know the answer please help, so I don't buy an engine I don't have a gear box for !!
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Old 01-12-2015, 09:49   #2
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Re: does 2gm gearbox fit 2gm20 engine?

Are the gearbox's from both engines marked KM2P? This should be marked on the top of the bellhousing, you will also find the gear ratio there, in my case 2.62:1
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Old 01-12-2015, 11:51   #3
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Re: does 2gm gearbox fit 2gm20 engine?

Recently swapped out an original KM2 transmission on my 3GM 30 for a KM3 transmission. There were some small casting differences with the Bell housings but the newer transmission bolted right in. The difference in the transmissions was the gear ratio, 2.2 on the KM2 and 2.6 on the KM3. Would be willing to bet Yanmar used the same transmissions for all the GM series engines.
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Old 01-12-2015, 12:32   #4
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Re: does 2gm gearbox fit 2gm20 engine?

Haven't checked the Transmission markings, the 2gm20 I'm buying doesn't come with a transmission

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Old 01-12-2015, 12:40   #5
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Re: does 2gm gearbox fit 2gm20 engine?

I believe the standard 2gm and 2 gm20 gear boxes have different model numbers, but wanted to see if anyone had interchanged the two. Could be just slightly different gearing like Roverhi mentions, but will the 2 gm box fit the 2gm20 ??

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Old 01-12-2015, 12:43   #6
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Re: does 2gm gearbox fit 2gm20 engine?

Is the new motor from a generator?

It will need more mods if it is.
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Old 01-12-2015, 12:48   #7
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Re: does 2gm gearbox fit 2gm20 engine?

Sorry I can't answer with absolute certainty, hopefully some of the Yanmar guru's will see your post and chime in.
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Old 02-12-2015, 19:58   #8
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Re: does 2gm gearbox fit 2gm20 engine?

Engines, bellhousings, transmissions all have an SAE. number. It means that these SAE. numbers must match. The numbers may or may not be on the transmission or engine. but can be researched on the internet if you know the model number. Many of the transmission dealers can help you with this, but I suggest you do as much research on this as you can.
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Old 02-12-2015, 20:33   #9
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Re: does 2gm gearbox fit 2gm20 engine?

Ring Minnard Marine just over your back fence.
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Old 02-12-2015, 23:50   #10
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Re: does 2gm gearbox fit 2gm20 engine?

Bought a used 2gm20, the story continues, waiting to get it freighted, should be interesting

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Old 03-12-2015, 01:06   #11
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Re: does 2gm gearbox fit 2gm20 engine?

Don't know about the 2GM/2GM10 but when I swaped my 1GM for the 10hp I had to have a plate made up to keep the prop shaft length. You could make a new prop shaft to length.

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Old 03-12-2015, 02:12   #12
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Re: does 2gm gearbox fit 2gm20 engine?

It isn't the prop shaft that concerts me it is mounting the old gearbox to the new engine ( coming with out gearbox)

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Old 04-12-2015, 05:27   #13
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pirate Re: does 2gm gearbox fit 2gm20 engine?

I don't really want to discuss why I don't rebuild my engine or weather it is my fault that the engine blew up, or if I preheat the engine or if I motor sail, or if I leave the engine in gear when the engine is off etc etc etc

Ha ha. Good one. You might have headed off some responses with that but I doubt; it didn't stop my thread drifting response here. Plus, your position is short-sighted.

The mention of the prop shaft length is a good example. There's no way you'd have thought of this; you should be more appreciative, sir, especially considering a) the cost of advice here, b) the fact that others want to contribute to this free forum in whatever way they can and some might lack your very keen sense of what's appropriate, and c) an aforementioned bit of knowledge (shaft length) that could vastly complicate what appears to be a simple question. Be careful what you wish for cappy.

You'd have driven me off but for my having interest in everything 2GM20F.
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Old 04-12-2015, 13:06   #14
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Re: does 2gm gearbox fit 2gm20 engine?

It is not that I don't appreciate all the responses, it is just that often the questions you receive are not related to the topic at all. Perhaps it sounded a little harsh, sorry to offend

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