Johnson FD-12 Gearcase rebuild

[DrummermanBob]

I am having difficulty with Johnson 1958 18 hp gear case re-assembly.  I can’t seem to get the two halves of the lower unit to seat properly. It looks as if the front of the gear assembly sits higher than the rear. I narrowed this down to perhaps the pinion gear sitting too high. When I put a narrower thrust washer on the pinion gear the assembly goes together as it should. Would it be okay to use a narrower thrust washer?

I also noticed that the pin that engages the forward gear bearing is missing (sheared off ??). Any thoughts on how to keep that bearing from rotating without that pin? Loctite? I really don’t want to drill out that pin. It seems like a bad idea to have that spin in the aluminum housing. Also, should the holes in the forward gear bearing face up and aligned with lube keyway? The pin likely aligned this but no pin.

Thanks for your insights.

[frankr]

Assuming it has the correct pinion washer, DO NOT substitute it.  Find and correct the real problem.  Do you have the gearcase removed from the exhaust housing?  If not, could the drive shaft splines be seized in the crankshaft and not being allowed to float up and down a bit?

[DrummermanBob]

Thanks for your reply. I can’t find any specs on that washer in order to be sure I have the right one. Short of ordering one ($35), I will continue to trouble shoot. The drive shaft is free to move in the pinion. The current thrust washer is very thick and it seems to make the pinion and forward gear over engage. This goes away with a thinner washer.

[fleetwin]

OK, well the gearcase was assembled before you pulled it apart, so something got changed while you had it apart.  Any new internal pieces/gears?  How about removing the prop shaft and gears, then trying to assemble the two halves….  If the halves go together OK with no internals, then there is some issue with parts you have replaced or how you have installed the original parts.  Are you sure no parts got accidentally mixed up with another engine/project?  Do you have the gearcase off, or are you trying to do this with the upper gearcase housing still bolted to the exhaust housing?  If so, I would probably remove it and secure the upper gearcase housing in a suitable fixture where it can be flipped upside down.  You mentioned the bushing locating pin being pressed into the housing, are you sure that bronze bushing is seated properly into the housing?

[DrummermanBob]

Lower unit is off and all were disassembled, cleaned and reassembled properly.  Halves seat properly without contents.

I purchased two FD-12’s and have been picking over each for parts. So maybe the mix -and-match is causing the problem although, I have measured key parts with micrometer and they are very close and wouldn’t stack-up to cause the issue I have described. The bushing locating pin is gone so nothing in the way of the bearing assembly seating properly. I still have to find a solution to that issue.

I will keep working on it.

[bobw]

Have you verified the rear gearcase head assembly is seating properly on it’s locating pin?

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[frankr]

DrummermanBob wrote:

Lower unit is off and all were disassembled, cleaned and reassembled properly.  Halves seat properly without contents.

I purchased two FD-12’s and have been picking over each for parts. So maybe the mix -and-match is causing the problem although, I have measured key parts with micrometer and they are very close and wouldn’t stack-up to cause the issue I have described. The bushing locating pin is gone so nothing in the way of the bearing assembly seating properly. I still have to find a solution to that issue.

I will keep working on it.

Whoa, you know that the skeg and upper gearcase are matched and not interchangeable with each other, right?

[jeff-register]

I had a forward bushing locating pin that was pushed into the hole as someone put together not clocked correctly & forced it up. & yes I second that  Frank! Can’t swap gearcase halves. They are machined as one piece, not interchangable. Was there something wrong with the original gears, shafts or shift dog?  Why were  you swapping parts to begin with? Are the 2 FD 12 motors the same year models. See I don’t know how long they called a FD 12. Maybe trying one gear at a time to find the problem? Pictures please.

[DrummermanBob]

Yep, gearcase head seats on locating pin.

[billw]

DrummermanBob wrote:

I am having difficulty with Johnson 1958 18 hp gear case re-assembly.  I can’t seem to get the two halves of the lower unit to seat properly. It looks as if the front of the gear assembly sits higher than the rear. I narrowed this down to perhaps the pinion gear sitting too high. When I put a narrower thrust washer on the pinion gear the assembly goes together as it should. Would it be okay to use a narrower thrust washer?

I also noticed that the pin that engages the forward gear bearing is missing (sheared off ??). Any thoughts on how to keep that bearing from rotating without that pin? Loctite? I really don’t want to drill out that pin. It seems like a bad idea to have that spin in the aluminum housing. Also, should the holes in the forward gear bearing face up and aligned with lube keyway? The pin likely aligned this but no pin.

Thanks for your insights.

Regarding the pin that holds the forward gear bushing from spinning, in my experience, they get driven into the gear case too far, when somebody tightens down the six skeg screws without lining up the pin with the bushing. One time, I very carefully drilled diagonally down (technically up) from the OUTSIDE, towards the pin and then used a punch to knock the pin back out, where it could be functional again. Then I used some Marine Tex to seal off the hole that I drilled. Not very elegant but it worked.

Long live American manufacturing!

[Author]

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