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AWESOME! have a beer and get that tranny rebuilt!

peace

can you try to have one made in the meantime? Ive had to do a lot of machining simple stuff for my motorcycle down here

making one in bronze or stainless for the meantime while you wait for the original might be of help to you
 

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Discussion Starter · #42 ·
I've done a fair bit of lathe work, but this one would be nasty, no specs, exacting taper, complicated mill jig, tempered steel, looks like a coating also. I have cutting tools with me, but nobody will let me rent their lathe.

I will ask at the shop if they can try. There's no quit in me, Ill get 'er done.

Dave
 

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Glad to have helped.

The 2GM20 had a single double-ended cone (I still have my old one), although I'd call it more than a "washer" - it weighs about a pound, the inside hole is a spiral thread that rides on the shaft; the outside is ridged and tapers toward each end, with a slot around the middle circumference. The stainless shifter dog rides in the slot (replaced at the same time) and moves it forward or aft, so the cone nestles into either of the counter-rotating drive gears. The spiral thread forces the cone to fully engage as a friction fit into the selected gear.

The shop I went to first "fixed" the knocking problem by "lapping" the cone into the gears, which lasted for a only little over one season (May-Sept this far north). When it recurred they lapped it again, which was a complete waste of time and money.

I just took a micrometer to the old cone, and other than some letters stamped into one end, can see no difference between fore and aft. I'd say (with a BIG caveat that I'm an electrical, not mechanical, engineer) that you could probably reverse it and use the less worn "reverse" side for "forward". I also wonder if milling a little off the face might let it engage further into the drive gear, depending on how far the shifter dog will let it go.

I also recall that several seals and such were "peened" closed and had to be replaced each time the transmission was opened.

Another caveat - on my C&C33, the external shifter arm had been repositioned 180 degrees to work with the Edson pedestal shifter (swapping push-pull/fwd-reverse), and when the second shop who correctly replaced the clutch cone reassembled it, they put the arm back in the "usual" position - now reversing forward and reverse on the shifter. Discovered that on the first day of vacation, so I drove the boat that way for a couple of weeks until I could pull the tranny again an have them re-reverse it (whence I learned of the seals that get changed each time). Make a careful note of which way the external shifter arm is pointing before disassembly.

In retrospect, make sure to leave these transmissions in REVERSE when sailing so that the prop forces the cone to engage reverse and stop any rotation. If left in Forward, the prop will turn the shaft spline in the sense that slightly disengages the cone, letting it rotate while still nested in the drive gear, slowly wearing it away. (It was interesting driving through Canadian Customs in reverse while I was unable to get it to re-engage in forward.)
 

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thats what I was told on my old 2gm too!

slap it in reverse and forget about it...

forgot about that here...good advice bud

christian
 

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Discussion Starter · #45 ·
So now I'm confused.

My tranny guys say the problem is the thin cone shaped washer which is actually outside the clutch cone. It rides somehow against a ' collar ' which buts into the cone clutch. On the main shaft, you first see bearing, then this cone shaped thing, then a 1/4" thick washer, then cone clutch assembly then another thick washer and cone thingy which shows obvious wear.

The shop guys seem to think the problem is caused by that thin worn cone.

My feelings say it's the big bronze assembly, as you think.

So where should I look on the clutch cone for suspected wear? I'd have to point it out to them.

As a historical note; about 25 years ago I lost a clutch cone to a cargo net crossing the South China sea. Obsolete ZF box, but a Phil machine shop knurled [ stamped ridges ] into the cone . I then used the motor in reverse with a right handed prop, across the equatorial counter current, back to the US.

Max speed 3 knots. . Ah, the good old days.
 

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Discussion Starter · #47 · (Edited)
My next door neighbor says this part is called a belvedere spring washer. I googled it and that is the beastie. Now , how to guess spring steel and tempering could be difficult, but not impossible

Can be ordered via auto cad specs if I can figure out the computer manipulations necessary.

Just returned from some very obscure crevices in Sing. They say that Belvedere washers with a 3" diameter would normally have a 1" hole in the center, not 2". This is a dedicated part; available only from Yanmar. This part does not exist in the old GM series, only new YM. It is a tapered cone, made of spring steel and phosphor coated and tempered. I learned that it could be ordered custom from fabricators but I would have a MOQ [ minimum order quantity ] of 100. And 6 week wait.

Off I go to Dalac Marine. Carpe diem
 

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Discussion Starter · #48 ·
Six months later, now in Gulf of Siam, 40 miles from Cambodia.

Dalac Marine owner misled me because he didn't want to order parts from Sing. The dealer there said the parts could never take more than 3 weeks because that is the time to air ship the parts. When I ordered the Belvedere spring washers [ $6.00 each ] they arrived in 10 days.

Dalac mechanic installed parts but installed the interior shift arm upside down which caused the box to lock up after one use. Gearbox out again and angry mechanic spilled the oil everywhere and finally got it right.

200 hours later; system now functions well. I could indeed have used reverse Belvedere spring washer as temporary fix, losing reverse gear til replaced.

Note to the next person with this problem; Taking the gearbox apart takes a large vice to hold the rear transmission flange and approx. 150 ft/ pounds of torque on that flange nut. Then main shaft with defective parts can be replaced

Reassemly. Don't forget to bend the locking tab on flange nut, make sure shift rod rests on top side of main shaft, and remember to fill with oil when reassembling.

It will be extremely difficult to do this onboard. maybe a huge pipe wrench on the flange and a 1/2 or 3/4 inch ratchet with a pipe over the handle as an extension. I believe the large nut is left hand thread. Good luck !!!!!
 
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