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Tohatsu B18D, gear problems.

K

Kristoffer Stavros Alm

New member
Hi!

I have a very old Tohatsu B18D but from what I can find out it is more or less the same as M12A.

My problem is that it is stuck in gear all the time. I took the lower unit of and also the propeller-shaft. From what I can see, there is a small round piece of metal that interconnects with the gear shifting rod. When the rod gets pushed down - the metal piece push the gear on the propeller-shaft. I think the problem lies is that the metal piece that pushes out does not go back in again. The construction of the gear shifting rod is made so that it only push the metal piece out - the the piece is supposed to go back in by itself, which it doesn´t.

Am I missing any parts in the propeller housing? The first thing that comes to mind is a spring that would gently push the metal piece back in to allow for neutral and forward gear. There is a spring inside the propeller-shaft but it is locket with a screw. I found a picture of another old LU that can show my issue.problem.JPG
 
Thank you!

The spring is strong but located inside the shaft where it's locked in place with a screw at the end facing the gear changing "pin" meaning that the pin and the screw connects. Then there is no possibility for the spring to actually push the pin.
 
AFAIK, all 3 gears stay in cog all the time. The vertical cam rod pushes on the push rod, which presses the clutch dog against the spring. Raising the cam allows the spring to push the dog forward. Having never had a motor that vintage apart, I can't say with certainty, but I don't recall there being any screw in the prop shaft at all on newer models.
 
Thanks again for taking the time to reply. I will take it apart again today and check it. Since it´s so vintage, it´s hard to find a parts diagram or service manual. I emailed Tohatsu Japan but they haven´t replied... I also tried to look at similar HP and year from Mercury and others but have not found any diagrams that are the same...

/Kristoffer
 
I think I found the problem. It´s not the spring in the propshaft. The reverse gear has quite a big play on the propshaft - about 5-8mm vertical. I think this causes the reverse gear to slide away from the planetary gear when the prop starts turning and pulling away. Has anybody a parts diagram for the B18D/C that shows the gear housing and gear parts?
 
Tohatsu B18D does anyone know where i can buy a water pump replacement that will fit the Tohatsu B18D 9.8hp motor.
 
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