Shaft Coupling for Yanmar 2QM15

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Nov 10, 2012
62
Catalina 36 mkII Havre de Grace, Maryland
Has anyone replaced their Shaft Coupling on their Yanmar 2QM15 Diesel? Mine is very corroded in my 1980 Hunter 30. Can a reasonably handy sailor replace this themselves while the boat is still in the water?

Thanks!
 
Jun 8, 2004
1,061
C&C Frigate 36 St. Margarets Bay, Nova Scotia
It can be a real bugger to get a corroded shaft coupling off the prop shaft. I disconnected the coupling and slid it and the shaft back a couple of inches. Then I put a socket from my tool box with a slightly smaller diameter than the shaft between the coupling and the gear box output shaft. By using longer bolts to connect the coupling to the gear box flange with the socket in place, I was able to 'press' the shaft out of the coupling. There is some risk of damaging the gearbox output shaft and flange in this method. Give everything a soak with a penetrating oil first...tighten the bolts evenly...and take care!
 
Oct 25, 2011
576
Island Packet IP31 Lake St. Louis, Montreal
If you can slide the shaft back far enough, you can aslo use a gear puller. Taht;s how I got mine off a few years ago. You should be able to rent one for a reasonable fee.

Cheers

Matt

 
Mar 20, 2007
500
Catalina 355 Kilmarnock, VA
You could have a proper plate-type puller made pretty readily by a machine shop, or for $32 you can buy one from deepblueyachtsupply.com that is purpose-made and won't risk bending or breaking the transmission flange or the coupling. I just bought one (along with a new coupling) from them, to replace the bellows on my dripless shaft seal.
 
Jun 21, 2007
2,117
Hunter Cherubini 36_80-82 Sausalito / San Francisco Bay
... "Give everything a soak with a penetrating oil first...tighten the bolts evenly...and take care!"
On the above from Jim about penetrating oil, I remember that Maine Sail in one of his a "how to" articles about re-packing a stuffing box (I think that was the article anyway), noted that penetrating oil must not come in contact with the gear box output shaft seal which is easily softened and then prone to leak. I don't have experience with any work in the area, but would make sense to take precautions before applying PB Blaster type stuff to the coupling area. Just a mention.
 
Feb 6, 1998
11,701
Canadian Sailcraft 36T Casco Bay, ME
On the above from Jim about penetrating oil, I remember that Maine Sail in one of his a "how to" articles about re-packing a stuffing box (I think that was the article anyway), noted that penetrating oil must not come in contact with the gear box output shaft seal which is easily softened and then prone to leak. I don't have experience with any work in the area, but would make sense to take precautions before applying PB Blaster type stuff to the coupling area. Just a mention.
I also very STRONGLY caution against using the gear box flange for removal of the coupling. It is VERY, VERY easy to bend it. Once it is warped ther eis no "facing it". I show "how" to do it but do HOPE people listen to my very strong CAUTIONS...

The SAFEST method is to cut the shaft and replace both it and the coupling. You will need a fit and face once it comes apart anyway and 98% of the time you also need a new coupling.

My cautions:

WARNING !!!!! Unless your shaft is very new, like this one was at just a few months old, be VERY, VERY careful using this method.


I hate to even suggest this method but it "can" work. There are shaft couplings that can be removed this way, if you are very careful. Please be aware that it is VERY, VERY easy to bend a gear box output shaft, making future alignments near impossible, or actually break one see photo after this one. A better method is to have a plate made at a machine shop with the same bolt pattern as your coupling and use it to press the coupling off NOT the transmission flange.


If using this press off method it will be IMPERATIVE that you take both the coupling and the shaft to a machine shop and have it tested for run out and then perform a "fit & face" before re-installation. It takes VERY, VERY little force on these couplings to throw them out of true. Throw it out of true and you'll cause shaft whip and will have a boat that is physically impossible to align! Do not cut this corner..


This coupling came off easy compared to many. Still when I took it to the machine shop it was out by 7 thousandths. Lucky the gear box flange still spun true. I suspect this shaft came from the factory with an improper "facing". This would have made for an impossible alignment..

and an example:


Please DO NOT over tighten the draw bolts. This boater was very lucky he broke the shaft flange and not the gear box flange. Despite his gear box flange not breaking, it was thrown severely OUT OF TRUE. The only way to fix this is with a rebuild.

Despite the gear flange not breaking it still cost $1750.00 to fix the BENT gear box output flange which required a re-build of the gear box. Remember these flanges are going to be aligned to 0.003" when you put her back together. It does NOT take a lot of force to bent the output flange by 0.003".

If the coupling won't come off you can cut the coupling just over the key way as seen in this photo. Creating the cut at the key way will ensure that you don't damage the shaft. One cut it will relieve the pressure and the coupling will then come off.

If you can't get an angle grinder in there to cut the coupling you may need to cut the shaft. Not all couplings will come off so PLEASE don't ruin your transmission in the process.


$1750.00 is a LOT more than a new shaft & coupling......;)
 

RichH

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Feb 14, 2005
4,773
Tayana 37 cutter; I20/M20 SCOWS Worton Creek, MD
Many of the shaft couplers on QM series engines were set up with a tapered end shaft in the coupler.

How to verify:
Remove the coupler bolts and slide the coupler back away from the transmission, sufficiently in distance so that you can 'see' or feel with your finger if there is or isnt a LARGE nut on the end of the shafting. If there isnt a NUT on the 'nose' of the SHAFT, then this is a straight shaft connection ... and then follow the advice given in the other posts.

However, if you see/feel/find this large NUT, remove it, and then 'strain up' the coupler as with a 'straight shaft connection', .... remove any 'set screws, etc.' apply 'strain to the coupler as a straight shaft connection ....... and simply whack the side of the coupler with big lead hammer or with a steel hammer onto thickly folded 'cloth' held to the side of the coupler base (not the flange) ... usually the tapered coupler and tapered shafting will simply 'pop off' with a few 'whacks' - when the shaft to coupler connection is TAPERED (has a BIG nut on the shaft 'nose').
 
Jun 4, 2004
834
Hunter 340 Forked River, NJ
Space

I had a 1980 H30 with the 2QM15 engine. There is very little space available on the shaft to work on the engine flange and even the stuffing box. You can unscrew the stuffing box and barely move it forward enough to get enough space to remove and replace the stuffing flax. Another concern is that there is limited access and you can do most jobs with only one hand. Sad to say but it is likely that you might have to move the engine into the main salon in order to work on the flange. You also have to remove it to pull the shaft because of the rudder skeg.
 
Nov 10, 2012
62
Catalina 36 mkII Havre de Grace, Maryland
Thank You!

:eek: Wow, thanks for all the great feedback on this post. ~Ed
 
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