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jag39 · 16-07-2018, 13:37

Not sure what box you have, but the MS gearbox with the reduction gear on the rear, requires no disassembly to replace the rear seal. Have to remove the propeller shaft and that's it. The seal is visible on the rear without taking anything off. Post a pic, and I'll know for sure if it's the same box. Very easy repair, though the seal is about $100. Just redid mine along with some internals.

DougR · 16-07-2018, 18:04

To answer your question, yes, you can remove the reduction housing #73 to change the seal leaving the rest of the box in place.....but as Jag 39 points out it might not be necessary to even go that far to do the job.

First thing is you have to unbolt and slide back the prop shaft coupling to give working access. Then remove #79 which is a large rubber dust wiper which sits on/surrounds #82 the reduction gear/companion flange and lays against the oil seal itself, #78.

Now you can see #78 the seal. If you can slide a seal hook under the seal lip you might be able to pull it out without going into the box any further. Careful that you don't scratch the sealing surface of #82 or you might have future leak issues. If you get the seal out, the installation of the new seal is just the reverse of what you have already done......put it all back together and relax!

If you can't get the seal out with a seal hook you will have to remove the reduction gear #82 to get better access to the seal. Remove items #87 down to #83 and use a puller on the reduction gear/companion flange to remove it. Place a spacer on the inner threaded boss to protect it from damage when using the puller. This should give you the necessary access to remove and replace the seal,
and then everything goes back together in the reverse of its disassembly.

It's probably a good idea to obtain a copy of the manual to read up on everything before diving in.

DougR

Bill Seal · 16-07-2018, 18:23

The rear seal is a pretty common 4" seal, about 10 bucks at your friendly local bearing house.
Just measured my spare gearbox, 4"ID, 4.75"OD.
I cut down the final gear to 3.95"OD to get rid of the pitting, and it still didn't leak.
A word of warning! If you pull the gearbox off the engine, first put a tarp and lots of oil pads down in the bilge, there's a quart or two of oil in the bell housing which will come cascading out when you loosen the flange.

Ngre · 17-07-2018, 14:23

Thanks guys for your responses , appreciated- hopefully I’ve uploaded a couple of pics to identify the gearbox

Chaser413 · 30-09-2018, 07:03

Quote:

Originally Posted by aquafacts

If you need a complete MS box - let me know - I have several from fresh water applications - Gear ratio ?

Do you have a cone clutch for this? Or just. A complete MS.
Mine has a V drive. Mine is slipping on engagement in forward but locks in after a few seconds. Makes maneuvering in close quarters interesting.

Bay_Sailing · 09-10-2018, 23:28

There is a splined driveshaft that goes about 3/4 The way into the reduction gear. I doubt you would be able to push the prop shaft that far back.

Scuba · 03-11-2018, 13:44

Quote:

Originally Posted by aquafacts

If you need a complete MS box - let me know - I have several from fresh water applications - Gear ratio ?

Hello Do you have contact info , may be interested in a Ms gearbox i have a MD17 C with 1.91 ratio

thanks

Keith

Bay_Sailing · 06-02-2019, 22:19

For the last few months I have been rebuilding the MS reverse gear attached to the MD11-C in my Cheoy Lee Clipper 36. I bought a replacement that shifted ok and also got a replacement timing gear cover. I moved the engine into the cabin using 2 Super struts as rails, chains, bottle jacks, the mizzen mast winch, etc. All bolts and studs were replaced with new Volvo replacements. I opened up the reverse gear and replaced the front oil seals. Both reduction gears were rusted out and leaked oil. The shelf of reduction gears mentioned earlier are now at a marina in NW N.Y. - French Creek Marina 1 315 686 3621 They rebuild MS reverse gears there and will sell a reduction gear for $1700. A company in the UK, Friction Products, will refurbish the friction cones. I found a new reduction gear on eBay and paid $20 for it. My engine is all assembled and running,

Bay_Sailing · 26-02-2019, 16:55

I just bought a new shift shoe, PN 839646, from a seller on eBay. It makes it much easier to shift into neutral, so I was confident enough to motor out and go sailing last weekend. I will be replacing the Morse cables as well. The current ones are very old and may have backlash. I took some pictures of the old (left) and new shift shoe before installing it. When installing the shift shoe, the 7 faces forward. The deeper part of the curve, visible on the left side of the shoes in the second picture, goes on the starboard side. If the shoe is put in backwards it will be jammed. A telescoping magnet pickup tool is handy because the shoe will inevitably drop into the transmission.
The old one is much thinner from wear, although it does look to be deeper. I would recommend buying one for anyone with an MD11-C engine with problems shifting into neutral. I noticed a big difference. Slow idle speed also helps.

Chaser413 · 08-04-2019, 06:35

Is the 7 supposed to face towards the engine? You said forward but I have a v drive and the engine sits aft of the transmission.
Thanks

DougR · 08-04-2019, 14:02

I dont remember if the 7 goes toward the engine or not, but you will notice that the shift shoe is not symmetrical around its shaft....
One of the "points" sits deeper in the groove than the other one, and this deeper point has to "wrap" around the groove because the shifter doesnt sit in the middle of the cone, but is offset to one side.

If installed the wrong way you wont be able to get the shift cover bolted down on the case.....the deeper point will jam into the cone.

DougR

Bay_Sailing · 14-07-2019, 22:31

The side of the shoe with 7 stamped on it should face the engine. You will know if you have installed it the wrong way because you won't be able to tighten the cover all the way and the shifter will be jammed.

Six months of engine operation with the rebuilt transmission and no major problems. The idle position of the cockpit shift lever is a bit off-center. This makes it difficult to put the transmission in idle. There is no room in the cable adjustments or by moving the bracket to fix this. I will have to make another morse cable bracket to fix that problem. The engine runs cooler than it did before. The new reduction gear is not clogged like the old one and I used bronze hose fittings with a larger ID.