No Forward or Reverse

[Dean Strong]

1990 Hunter, Yanmar 2GM20F.

Went to use the boat Saturday, and backing out of the slip noticed much less response than normal; just enough to get backed out. Went to put the boat in forward, and nothing. Then reverse; nothing. Left adrift. Managed to get back to the slip. Then checked transmission linkage, cable connection, lever movement on the transmission, all was working. Put it in gear, shaft was turning in both directions. Took it up to about 2000 rpm, and all looked fine.

Thought maybe prop nut and prop had come loose, and on return to dock, running the engine in forward forced the prop back onto the shaft. Hired a diver to check, and he said all was tight. Hauled out yesterday, and indeed all is tight; no evidence of any slippage and prop nuts are very tight and obviously haven't moved since last haul out.

So what happened? I don't know how these transmissions work. Is there some kind of a friction plate (like a clutch plate) in the transmission that could have been slipping? What should I be looking for? Something clearly is not right.

 

[Squidd]

Check this out...

http://www.sailnet.com/forums/diesel-engine-forum/91426-slipping-prop-troubles.html

 

[navigator97]

Dan,

I believe that it is gear teeth that mesh. There is a 2.61:1 gear ratio from engine to shaft. If shaft is rotating, as seen from inside the boat, and the prop is attached securely, then you should have good prop rotation and drive... It's a mystery why you would not have propulsion. have you tried it again in gear while securely tied up in the slip (secure in both directions)?

 

[Dean Strong]

Yes, I tried several times to engage at the dock, including when the diver was there, and all was fine. If the transmission works by meshing teeth, there is nothing in it to slip. It could only be the key way, as suggested by the provided link. Other thoughts?

 

[Squidd]

Nope... I think your keying in on it...

 

[Joe23455]

is your gearshifter on your pedestal in working order , is it sloppy in either direction ?
does it move with to much freedom?

just a thought

 

[woodster]

sounds like a cable clamp has come loose and slipping ...check the cable hosing where it fasten the the bell housing and also at the shifter and make sure they are secure or you could have had the fast idle button pushed 1/2 way in or out and caused it ...just some thoughts .....

regards

woody

 

[zeehag]

morris cable ends need attention--perhaps is wearing out or breaking....or could be that there is a set of bearings in the tranny may have issues-they look like wheel bearings that wear out . my neighbor had that issue--came into the anchorage with only forward--no reverse no neutral and had to be talked thru anchoring....now is fixed--but had to disassemble tranny to find bearing problem. his tranny ran dry --he ran it sans oil for a few miles....


good luck and may the problem be solved easily .
.

 

[Steve Dion]

You may also want to check that cable housing attachments. If you have a Y/S pedestal there is a screw on the forward postiion of the pedestal and then another on/near the tranmission. If these slip you will not get full engagement of the transmission.

 

[quietriot]

I would make certain that the prop is keyed to the shaft via the keyway and key. If you see it turning inside then the problem might be outside.

 

[Benny17441]

If the shat is spinning and there is no thrust remove the propeller to see why it may be slipping.

 

[CNussbickel]

Of course the transmission has a clutch plate in there. That's one of the reasons you're supposed to idle down before going from forward to reverse or vice versa.

 

[Dean Strong]

Clutch plate

Of course the transmission has a clutch plate in there. That's one of the reasons you're supposed to idle down before going from forward to reverse or vice versa.

Like I said, I don't know how this transmission works. If there is a clutch plate, how does it work, and can it slip so the gears do not engage? Thanx

 

[Stu Jackson]

Transmission resources

Good advice, as always.

Here's another "tack" for you to consider --- forget for a moment what your engine is, your issue is your transmission

So, find out which transmission you have on your boat, and then Google it and learn how it is built.

www.marinedieseldirect.com might help.

Good luck.

 

[woodster]

Like I said, I don't know how this transmission works. If there is a clutch plate, how does it work, and can it slip so the gears do not engage? Thanx

there is a damper plate that is bolted to the fly wheel with a female spline that the gear box main shaft goes through with male splines on it when the gear box is bolted to the engine....if it was bad you would know it as there would be a lot of strange and sicking noise coming from that area...the reason it would be sicking is that it cost about two hundred bucks or more... along with having to pull the gear box and rear bell housing to get to it to replace it...and could be worse you might have to pull the engine to get all that out ....there are 4 springs in the make up of the damper plate to absorb the shock of going in and out of forward or reverse but from your description i don't think you have that problem ....just trace the shifter from one end to the other and check every connection involved in the control system and you more than likely will find the trouble....

regards

woody

 

[kloudie1]

The 2 GM20F has a constant mesh (gears never un-mesh), cone clutch (as opposed to a multi-plate clutch) Kanzaki transmission. Interestingly the cones can slip if the shift cable does not push the lever on the transmission all the way into the detent.. If it is not going to the detents because of a loose cable clamp or a cable with too much friction, the shaft will turn at idle but it will not be able to transmit power at higher RPM.. With the boat tied up .. CAREFULLY (take off long sleeves and any arm jewelry that might get caught) put the shift lever in forward and look for water moving out the back of the boat.. Now go down and push the lever more in the direction it moved to get into forward.. now look for water movement .. advance the throttle and see if water moves.. If the coupling on the back of the transmission is turning and the shaft is not. your set screws are loose.. Check the oil in the transmission and make sure there it is up to the proper level.. If it is black and really thick, you may have worn clutch cones, but usually one set will wear first, leaving you with either forward or reverse.. So if it was working and not making a bunch of noise before, you probably have a loose or corroded shift cable or you have a shaft thet may be loose in the coupling (assuming thatt he diver was correct when he said everything was tight).. Good Luck with it

 

[Stu Jackson]

1990 Hunter, Yanmar 2GM20F.

So what happened? I don't know how these transmissions work. Is there some kind of a friction plate (like a clutch plate) in the transmission that could have been slipping? What should I be looking for? Something clearly is not right.

Kloudie nailed it, if you have a Kanzaki transmission. Simple from there, step-by-step.

Many times, regardless of the type of transmission (note that i didn't call it a "tranny"!), the linkage is the very first place to look. Move the lever that is ON the engine. Then check the cable connector to the binnacle.

Good luck.

 

[SamLust]

On that gear set the engagement cones wear over time. Often as they age engagement becomes inconsistent. In '98 or '99 it cost me about $450 for a rebuild at Mack Boring, which of course cured the problem.

You are assuming the diver is correct. If the shaft KEY at either the engine coupling or the prop has sheared it could be very difficult to determine from below while in the water. The nut alone will create enough friction to make it appear the prop is well fastened while in fact the key might be sheared. Pull the prop and inspect the key. For that matter pull the shaft from the coupler and inspect that key also.

 

[Eric M]

Have you checked the shaft to transmission connection? These are notorious for failure and when you are in reverse the prop is trying to pull the shaft out of the boat. When you are in forward the prop is pushing this connection back together.
Let us know what you find.

 

[Dean Strong]

Low Transmission Oil

So far the only thing I've found is that the transmission oil is very low. So low that when I stuck my little finger in the hole, I couldn't feel any. Now before you laugh, or shake your head, in 15 years this boat has never consumed ANY transmission oil. I check it about once a year, it is always at the top, and always clear and clean. I change it when I change impellers, about every other year. Because it is not a problem, I am not in the habit of checking it at every start up, like I do the engine oil. That will now change.

There is no evidence of any leaks, anywhere, so I don't know where the oil went. The only thing that has changed, is that after all the debate the past couple of years about sailing in neutral or reverse, I switched to neutral after reading the Yanmar bulletin. Before that, I always locked the transmission in reverse. Perhaps the shaft spinning while sailing creates more heat, and consumption, though I understood that the shaft, but not the transmission, turned while sailing in neutral.

Anyway, I'm changing the transmission oil and hoping that I still have a workable transmission. I'll let you know what happens when I get back in the water this week. Some of your posts were very helpful