Merc 100 gearbox stripdown: HELP!!

[kwik]

Hi everyone, this is my first post, so hello to you all!<br /><br />I have a 68-69 Merc 100 that I have fully rebuilt, but it has a problem with the gearbox, hence there is no reverse. This I think is down to the little pin that gets pushed back by the gear selection cam, as it doesnt seem to push back far enough. So i started to strip down the box, but i could only get as far as removing the large circular castle nut, and the stainless washer underneath: See pic below:<br /><br />

<br /><br />After this the drivetrain carrier seems to be firmly stuck in place. I have tried soaking in parafin then heat, and brute force but it seems firmly stuck. I then fashioned a home made puller as can be seen in the pic below: <br /><br />

<br /><br />...but this is of no use as when the nut is turned it ratchets the gears. (would have been no prob if i had lost forward gear and not reverse!)<br /><br />Is there a special tool i can buy to remove the carrier assembly? Any help to this matter would be greatly appreciated as this is the only thing stopping the motor going back on the boat. Thanks in advance, Mark.<br /><br />ps here are some more pics of the rebuilt engine if you guys are interested <br /><br />

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[seascavanger]

Re: Merc 100 gearbox stripdown: HELP!!

HOLD ON! Don't start hammering yet. You need a manual. You can use a screwdriver to unscrew carrier by wedging it just right and tapping it counterclockwise but I wouldnt recommend it as it will start denting bearing. If you do it, first remove little square pin at bottom that keeps it from turning.

 

[kwik]

Re: Merc 100 gearbox stripdown: HELP!!

Are you sure? I have already removed the large castle nut that holds the carrier in place. Its the actual carrier itself that i need to remove. In theory and an ideal world it should just lift out. But due to corrosion, it seems firmly stuck. I cannot seem to find a way to pull it up. Any thoughts?

 

[seascavanger]

Re: Merc 100 gearbox stripdown: HELP!!

OK, look carefully around threads at very bottom.(south....when facing upright) The pic shows rusty dirt so its hard to see and has to be clean to see well. Its a square slot (1/8" by 1/8")....That sqaure pin has to come out before carrier will turn. (clean and oil,then pick out with tweezers...........let me know....ive been there,done that

 

[Laddies]

Re: Merc 100 gearbox stripdown: HELP!!

Mike, I use the prop instead of the spacer you are useing that way I can hold the shaft--Bob

 

[rodbolt]

Re: Merc 100 gearbox stripdown: HELP!!

the carrier does not turn out.<br /> just the spanner nut and usually I have to cut them.<br /> either precision tools or B7K make a super nice puller. I use the J bolts that are actually for OMC v4-v6 lowers and a harmoninic balancer puller body. but oxy-acetylene will be mandatory. the alighnment pin will pull out with the carrier and its tiny. dont lose it. if you try to pull very hard the brass prop nut just strips. the one merc sells is as useless as the one yamaha sells. works well at the school house but not in the field after a few years of salt.<br />however your also supposed to take the carrier out once per year accourding to the maint schedules.

 

[bh357]

Re: Merc 100 gearbox stripdown: HELP!!

The service manual says to clamp the propshaft firmly in a vise between 2 blocks of wood, then tap lightly on the skeg. YEAH RIGHT!!! That may have worked in 1971 when that motor was only a couple of years old. I ended up having a shop pull mine. They ended up having to use heat and a puller. I personally lacked the confidence to heat up aluminum parts.<br />Since then I have used the prop to pull the carrier. Leave the plate on as in your second photo, slide the prop on, then tighten the nut. I wouldn't recommend doing that with a bearing carrier that probably hasn't been pulled since Nixon was in power.<br />Be sure that you clean the carrier and the housing inside (where the carrier slides into) really well before reassembly. I used emery cloth (600 grit?), and a generous coating of Mercury grease. You never know when you may need to crack it open again <br />Be prepared to find a worn shift cam, worn cam follower, and worn clutch dogs.

 

[seascavanger]

Re: Merc 100 gearbox stripdown: HELP!!

I did my 1970 135hp about 5 years ago and had the shop use his tool for the final tightening. Its probably time for a reseal. Those wave jolts must be workin on my memory

 

[kwik]

Re: Merc 100 gearbox stripdown: HELP!!

Hi people, thanks for all the replies! I actually had the same idea as Laddies (see above) with using the prop as something to hold onto. Firstly the little rectangular locating bit was virtually was impossible to move, and the gearcase looked like it had never seen daylight since '68! So i modified my plate i was previously using with the bit of pipe and put four cuts in it about 1/4" in size. These let the carrier come right up. See pic: ps i know its as rough as a badgers arse, but it needed to be done quick!<br /><br />

<br /><br />I then put the prop on top of this, and wedged a 4"x4" block between prop blades and where the trim tab sits. This kept it from turning, and also the splines on the prop stops the shaft turning which was my previous problem.<br /><br />I then packed the top with thick washers, making sure the bottom few were of a greater diameter than the widest part of the driveshaft (this was found out after some head scratching!) the brass nut held its threads as it was tightened, massive heat was applied to the gearcase by means of propane torch. By working in parafin as the gearcase was hot it let it get between the carrier and the gearcase walls, this really helped!<br /><br />

<br /><br />Then it was the case of turn the nut as hard as you can untill the carrier comes out!! It worked!!<br /><br />Once the shaft and carrier were removed i could inspect. It appears that the reason reverse isnt working is not due to the cam or the dog, as these are worn but still workable, it was infact the reverse cog itself.<br /><br />The inner of the cog, where the dog engages was separate from the actual toothed area of the gear cog. Hence the dog would engage but the cog would remain stationary. I've never seen anything like this before! Pictures of the broken gear will follow shortly!<br /><br />Thanks again for all your help guys.<br /><br />Mark.