Possible Yanmar Transmission Damage

[Wotname]

Originally Posted by Catcruiser

.....
On topic: on conical Kanzaki gearboxes you should leave your prop free running. In gear, there is constant pressure of the prop wanting to turn. .......

OK but WHY. Apart from vague references to possible "damage", I have been unable to find any reference to a credible explanation of what actual damage occurs. So what if the there is a constant pressure on the prop (providing it doesn't actually turn). The gearbox is designed to accept 20+ HP from the engine and deliver it to the prop so some pressure from the prop is ......
And why has it taken decades for such an advisory to be issued.

[four winds]

A topic of interest to me as I have a 3GM30F with a Kanzaki v-drive.


I have always sailed in neutral and actually haven't found the turning prop and shaft to be annoyingly loud for some reason. After reading that here I looked to make sure it was turning while sailing. It was and now I can hear it through the wind and waves noise. Maybe my boat structure attenuates it more than others.


One time (one time... at band camp ) I accidentally left the trans in gear, but frankly I can't remember if it was forward or reverse. At any rate, when I wanted to start the engine I noticed the error and found the shift lever took a very strong effort to disengage the gear. That concerned me but no apparent damage was done.


As far as the slipping and polishing goes I can see one way this could happen.


I had to rebuild my shifter (related to improper lever and cable setup for A4 and a failed plunger spring) so I've seen the inside and had to study up for the repair. In my opinion, if the shifter was not adjusted properly even by a small amount it could cause a situation where slipping and polishing of the cone could occur.


It could even function well enough while being driven by the engine yet slip when in the sailing in gear.


This is because the forces on the cone and gear would be in the opposite direction from the normal operating mode when sailing in gear. In other words, the load is reversed. And therefore opposite to the direction the parts were designed to operate.


Combine that with a improperly adjusted shifter and there could be a problem with the friction fit of the cone and gear over a period of time. A wearing down of the oil grooves would compromise the function of the cone. And the shift plunger would be in contact and wearing at all times as well.


my opinion.

[sailorboy1]

Originally Posted by Catcruiser

Yet another Yanmar recommendation: do not install a folding or feathering prop under your boat if you DO NOT have a flexible coupling between shaft and gearbox.

I did a search and and could no reference from Yanmar saying this. Yanmar even is promoting the Gori props and there isn't any mention in that section either.

[Lowcountry]

I have a 2006 3YM30 in my boat, and I have sailed with the transmission in reverse on two occasions, about three years apart. Each time, my transmission bound up and I broke my linkage (inside the binnacle) trying to get the transmission back into neutral, requiring the entire cable to be replaced both times. Not fun. I would much rather listen to the prop shaft freewheeling (which is hardly even noticeable) than have to replace my transmission linkage again.

[Wotname]

Originally Posted by Lowcountry

I have a 2006 3YM30 in my boat, and I have sailed with the transmission in reverse on two occasions, about three years apart. Each time, my transmission bound up and I broke my linkage (inside the binnacle) trying to get the transmission back into neutral, requiring the entire cable to be replaced both times. Not fun. I would much rather listen to the prop shaft freewheeling (which is hardly even noticeable) than have to replace my transmission linkage again.

Ouch... Out of curiosity, did you try starting the engine while the transmission was still in reverse and "bound up"?
I can't imagine being able to put enough force on my gear lever / cable setup to break anything but I appreciate you have a different setup.

[deltasig]

I experienced similar behavior with the engine/transmission in reverse after sailing from Skyros to Psara (58nm). The engine would NOT start with the gear engaged! and ... since I decided to sail into the port, I started panicking because even with the sails down I had quite a bit of way. Fortunately, I was able to make a U turn; only after the boat came to a halt I was able to switch to neutral and start the engine and an old problem re-appeared. In forward gear past idle speed, the transmission would shake violently. I took repeated cycling of the gears to F-N-R-N-F to finally engage and run without vibration. I reported this problem in the forums in 2010 and I thought I fixed the problem after adjusting the travel of the shift cable.
Which brings me to the question: how much of a job is it to remove the transmission, open it up, lap the cone(s) and put it back together? Boat is on the hard now.
I read somewhere that one has to replace seals (front and back), dumper plate and possibly gears. Could someone who has tried this (lapping of cones) give me some more insight. Thank you.
BTW, I don't think that sailing with transmission in reverse had anything to do with the slipping of the forward gear; I tend to agree with a previous poster who suggested that an improperly adjusted shift cable could have cause the glazing of the forward cone.

[bill good]

I've just done mine & found it was easy to lap the cones. The only problem I had was trying to get the shifter to bits because of a missing spring & ball. I broke it before getting apart. I found a second hand one & it had the same top screw rusted. However by shaking the shaft & holding the case the shaft just slipped out!! Apart from that is was simple. Nothing worn beyond specs. Fitted new 1984. You should have the service manual. (avail on line)

Regards Bill

[roverhi]

I sailed to Hawaii from SF with the transmission in REVERSE. Engine shifted into neutral just fine after 2,118 miles. Put it in neutral very briefly after clearing the Golden Gate Bridge but the noise and vibration got on my nerves instantly and put it back in reverse for the passage. Engine is a 3gm30f with the 2.1 or something gearbox.

[deltasig]

roverhi,
what transmission year/make/model are you talking about?
Can you start the engine when in gear?
I have Yanmar 3JH2TE with Kanzaki KM3A and I experienced the aforementioned behavior more than once. Now I know that the boat speed has to be almost zero to attempt to switch to neutral.

Bill,
Did you have to replace any seals, gears or dumper plate?
How did you determine that the cone was lapped enough?
Thank you

[bill good]

Replaced the seals only. When you lapped the cones you will see the shine turn to a grey look & you can feel the grip. It was realy easy (after finding how to get that selector to bits!) The damper plate was just cleaned up & some grease applied. It must have been done before I got the boat for that spring & ball to be missing from the detent.

Regards Bill

[Northeaster]

I can see that the forces applied to the cone and gear, by the water rushing past the prop (in reverse) could cause glazing over time, as i think it would vibrate somewhat, with the softer forces applied, as opposed to the stronger connection made when 10 or 20hp is driving the cone into the gear.

I had to lap the cones, on my 1982 2GM about 4 or 5 years ago, and it worked well for a few years. A few months ago, had a couple of instances where it didn't go solidly into gear, and I will lap the cones again this winter. Have spent most of the last few years sailing with it in reverse, but will try to leave in neutral from now on.