YSM12 Coupler - Diagnosing a Potential Problem

[Mighty Little]

Ahoy. I figured my first post ought to be a good one, but maybe it's not.

After purchase the previous boat owner told me (after I launched) that the transmission coupler on the prop shaft side needed to be replaced, but neither I nor my boatyard guy saw anything wrong, nor can we seem to duplicate the described clunking sound.

(For the sake of this discussion let's ignore any of the potential political interpretations of the situation....I think it's an issue that came up for the boat owner at the tail end of last season and just wasn't communicated well to the broker. It would've been an easy fix on the hard, so I am told, though maybe more complicated in the water.)

There's about a 1" red plastic drivesafe in there that looks intact, the bolts I can reach seem tight and not stripped, yet we cannot seem to find an issue in forward, neutral or reverse, at idle or higher rpms.

I'm basically a total newbie at engine work so I'd love any advice or comment on how to really identify whether there's a problem. And if you've seen something similar, was it addressed in the water or did the boat need to get hauled and re-launched?

Thanks!!

 

[Ralph Johnstone]

There's about a 1" red plastic drivesafe in there that looks intact,

Can you provide a picture of the coupling ? This would go a long way towards getting a handle on the problem.

 

[Mighty Little]

Here you go!

 

[Ralph Johnstone]

The red plate between the two couplings appears to be a flexible coupling. Not clear on its function as the rubber hose attached to the base of the packing gland usually acts as the flexible coupling. What this red coupling has done is place your stuffing box in a position where the packing cannot be changed without disassembling the flange couplings. Not a good situation at all.

But one problem at a time. Do an alignment check yourself if you can or get your mechanic to do it. An alignment can be very time consuming but following the instructions is not too complicated. You really should start doing as much simple engine work as you can for two reasons:
1. You'll likely do a better job than the mechanic on simple jobs.
2. You'll save yourself a fortune.

Here's a good procedure for shaft alignment.

Discuss the red plate with your mechanic and let us know what he thinks.

 

[Mighty Little]

From what I've been told, the red plastic "drivesafe" is essentially the part that would break in the event of a grounding or prop fouling that would potentially otherwise break the coupling. It is an inflexible spacer with staggered lag holes for the shaft side and the drive side couplings.

Presumably upon loosening and removing the attachment bolts on both sides of the drivesafe it can slide right out, allowing the additional space needed to make the repair.

But I cannot even determine if there's a definite problem. I had a 4 hour shake down sail on this vessel yesterday during which we ran the motor for probably an hour to n the front side of the trip and a half hour upon returning. No weird noise or signs of problem at all.

Maybe at the end of the day the previous owner has sent my lookin for a bacon stretcher or left handed smoke shifter or some other bit of Boy Scouts nonsense used to train the young tenderfoot scout.

I'm working to get a 3rd party mechanic out there to run through everything as well.

Thanks for your comments Ralph.

 

[Mighty Little]

Have had three different folks look at this thing and they all thought it looked fine. Two of the four screws on the prop side aren't in great shape though. PO probably tried to change something and stripped one and broke one. The coupler-to-coupler bolts are all fine.

Today though, about 1/2 way out towards my destination running about 3.0kts on the motor in very light air all of a sudden I'm no longer moving. Prop started making some funky noises that were vibrating through the aft lazarrete so I throttled down and went and had a look. Everything spins like normal but no more propeller movement.

At first I thought maybe it was a fouled prop so I tried going into reverse and back into forward a few times. Still, no prop movement. I was single handing and didn't want to dive under solo and at this point the wind had picked up...so I beat it back home with a little help from a power boater to get to my actual mooring.

Did this coupler finally fail on me? At first I was able to spin the coupler SML shaft in neutral by hand but once I got back to the mooring and tried again it seems much tighter and I couldn't get it to budge at all.

Got some great single handed sailing in but damn, this was disappointing.

 

[Mighty Little]

Also, of the three people who have looked at this (one my boat yard all around guy, two a local marina mechanic, and three a surveyor/instructor/mentor-for-hire) and nobody seems alarmed by the red plastic part in between the flanges. They seem to have seen this before.

 

[NYSail]

The red spacer is a shaftsaver. Not flexible
And a good thing to have. Within the coupling there should be a key to hold shaft and make it spin. Perhaps the key fell out?? Take the coupling apart and see.....

 

[Mighty Little]

It's official. The set screws have sheared off. Looks like my mechanic will have to dive under to loosen/remove the zinc anode so the shaft can be pulled out a little bit...then he can head back inside to tap new holes for new set screws and then to put it all back together. Makes sense to me but too much of a project for me to do personally! And this isn't something I want to fail again.

 

[Mighty Little]

Well it took nearly a month but the coupler has been machined, new set screws, dimples drilled and all that re-installed. My guy is telling me I should get a new prop shaft on work order for the off-season. The woodruff key (do I have that right?) has begun shearing the keyseat round. Apparently some locktite and a bit of machining has gotten it back into usable condition for the remainder of the season, if I'm gentle on the transmission, but I'm likely looking at a new prop shaft project for the winter.

Any advice on that?

Any advice on folding vs standard propellers and if I should consider changing that while I'm at it?

-ml

 

[sesmith]

Yes, you will need a new prop shaft. While you have it out, you may want to replace the cutless bearing if there's any wear at all. The coupling will have to be fit to the new shaft and faced by the machine shop when you do it. Consider a split coupling, if you don't have one already. It makes assembly and disassembly much easier in the future, if needed.

 

[Mighty Little]

The coupler I have now is two parts - one on the engine side and one on the shaft side - is that what you mean by split coupling? Or is there another split, perhaps in-line with the direction of the shaft?

 

[lillia28]

ML, do some google searches, you can find the YSM shop manuals on line. The Yanmar installation manual shows a flexible disc between the coupler halves, but I don't think any boat manufacturer used them. A new shaft will most likely be stainless vs bronze, Its really not a big deal, a repeat of what you have just done, only with a new shaft. Change the cutless bearing while you have the shaft out. Only hang up is the way your rudder is configured, they had to drop my rudder, which is the only part that is not DIY, at least for me. Yanmar has both types of coupler available, the split and teh press on.
Lou

 

[Mighty Little]

Thanks Lou - I do have the shaftsaver in there and will plan to keep it. Will definitely replace the cutlass bearing while it's all taken apart. Research is also telling me there are different opinions on "upgrading" to a folding prop vs. keeping the one I have. More moving parts = more problems.

 

[lillia28]

Http://boatinfo.no/lib/yanmar/manuals/ysm op.html#/12
http://boatinfo.no/lib/yanmar/manuals/ysm12.html#/0
manuals there, I am looking for the parts list.
It's all about drag under sail. IMHO, unless you are a dedicated racer, I vote for a nice 3 bladed prop. You will go when you want to and slow/stop when you want to. IIRC at 6.3knts I spend an extra minute and a half sailing with the 3 blade as opposed to the folding prop. A life time in a race, barely enough time to get another beer on a typical sail.Take a look at the Campbell sailor prop. I am basically a daysailer/overnighter, so I am not crazed about being a bit slower under sail. If you are cruising under sail for 10-12 hours, reaching your destination 40 minutes earlier might be meaningful. The $$ difference between fixed and folding is significant. I am pulling my old ysm 12, let me know if you need anything. S2's are nice boats!

 

[Mighty Little]

Great info, thanks Lou!

 

[odaydokay]

Sorry you lost so much sailing time. Season is short enough as it is. Well, there's always Al's French Fries to hang out at..................

 

[sesmith]

The coupler I have now is two parts - one on the engine side and one on the shaft side - is that what you mean by split coupling? Or is there another split, perhaps in-line with the direction of the shaft?

Example of a split coupler:

http://www.propshopinc.com/4-YS-Split-Shaft-Coupler-Buck-Algonquin-10mm-Bolts-400YS-p33.html

 

[druid]

I'd be concerned as to WHY the setscrews sheared off and the keyway is damaged. Did you hit something with the prop?

I'm not a fan of folding props - get a nice 3-blade Campbell-Sailor unless you do a lot of racing.

druid

 

[odaydokay]

My view on both points also.....