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Old 25-05-2013, 01:00   #1
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coupling new engine

Hi guys

I think I already know the answer but will put it out to the masses.

I have just removed a 2qm20 and had previously bought a new flexible coupling for it which hasn't been used.

Problem is the new Nanni 3.30 I bout has a different hole pattern size so the engine coupler doesnt match up with the existing shaft coupler. Is there any tricks or do I need to buy a new shaft and flexible coupler that matches the Nanni?

Am doing all this whilst on a mooring so not really wanting to mess around with the shaft.

Any advice appreciated
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Old 25-05-2013, 01:29   #2
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Re: coupling new engine

you will need a matching coupling and flexible joint,about 200,all the specs are on this site,they may have a distributor in aus or nz


R and D MARINE : Flexible Shaft Couplings
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Old 25-05-2013, 02:31   #3
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Re: coupling new engine

If I understand you correctly, you may be able to make an adaptor plate with studs (or tapped holes) coming out either side to suit the respective patterns. I had to do this years ago when changing from a Volvo to Yanmar, and it has worked well.
Be aware that this will space the prop back the thickness of the adaptor so you will need to have clearance available.
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Old 25-05-2013, 02:56   #4
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Re: coupling new engine

Quote:
Originally Posted by boden36 View Post
If I understand you correctly, you may be able to make an adaptor plate with studs (or tapped holes) coming out either side to suit the respective patterns. I had to do this years ago when changing from a Volvo to Yanmar, and it has worked well.
Be aware that this will space the prop back the thickness of the adaptor so you will need to have clearance available.
Regards,
Richard.
this may also work,if you look on the r&d site one of their pdf files has all the register sizes,bolt spacing,and bolt sizes that you would need to make an adaptor,that would have to go on the engine coupling side.

though you will lose min 20 mm for the adaptor,and might work out more expensive in lathe time,and bolts.

you may also not have clearance for locknuts on either side of the adaptor flange,
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Old 25-05-2013, 03:34   #5
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Re: coupling new engine

hmmm. Intersting idea with the adaptor. First thoughts though is I dont know if I could make sure where the exact centre is. 1/2 a mil out and it will throw everything off when I mate them together. Will have a play around with it in the morning. I dont suppose you had any pics Boden from when you did it?
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Old 25-05-2013, 04:34   #6
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Re: coupling new engine

Sorry, no pictures. I just got a lump of scrap mild steel bar and whipped it up in the lathe. I am a rank amateur and it worked first go. An experienced machinist could knock it out pretty quickly.
If you get your work sequence right it is an easy enough job. You can use a cutting tool to scribe an appropriate line on the turned spacer while it is still in the lathe which will give you the correct diameter to set out the bolt holes.

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Old 25-05-2013, 15:18   #7
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Re: coupling new engine

Quote:
Originally Posted by atoll View Post
you will need a matching coupling and flexible joint,about 200,all the specs are on this site,they may have a distributor in aus or nz


R and D MARINE : Flexible Shaft Couplings
if you look on this site they give all the dimentions needed to make an adaptor plate ,with bolt hole diameter,bolt spacing,register size,and thread size for the high tenstion bolts of the two different couplings(nanni and yanmar,as well as most of the other common coupling sizes),not rocket science..........but enough to confuse your average aussie
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Old 26-05-2013, 10:19   #8
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Re: coupling new engine

I am surprised that the Nanni dealer who sold you the new engine didn't supply the correct shaft coupling with the engine.
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Old 26-05-2013, 10:42   #9
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Re: coupling new engine

Back in the day...... I installed a Volvo MD2B to a propshaft 1" in diameter and 17 feet long, with pillar block bearings for the first two frames 40" apart, then the shaft log, followed by the cutlass bearing. I had been carefully instructed NOT to use a flex mount shaft coupling because the bucking and vibration of the old two cylinder diesel would be maximized by the inclusion of another point of flex. It worked well enough so that when I replaced that awful engine with a Yanmar 3GM30F, I felt virtually no vibration, whatsoever.

My question, inspired by this OP's question, is: Does this same logic still apply to more modern engines? I take the time to align within 0.004", and the outcome is what I was looking for. Are mechanics now recommending adding flex couplings instead of taking the time to get the alignment nuts on?
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Old 26-05-2013, 11:02   #10
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Re: coupling new engine

Quote:
Originally Posted by boden36 View Post
If I understand you correctly, you may be able to make an adaptor plate with studs (or tapped holes) coming out either side to suit the respective patterns. I had to do this years ago when changing from a Volvo to Yanmar, and it has worked well.

Doesn't this require major machine-shop skills? Most coupling sets have a stepped shoulder to ensure that the offset (radial alignment?) will always be within a few thou.
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