1988 4 hp 2 stroke Yamaha lower unit

[Auminer_]

I need to raise the pinion gear a bit on the forward gear. What keeps the pinion gear from dropping down too low on the Forward gear? Guessing I need maybe a 1/16". As it is, it binds a little before turning then rumbles or grinds (gear noise) when rotating by hand. Probably something stupid simple, but...??

[Auminer_]

No response...??

Yup, I'm new here, but not new to life. Seems like a tech could come up with something helpful.

[99yam40]

being just bushings on the drive shaft and a plate washer, maybe a thicker washer , bushing bad or set wrong, housing messed up.
hard to tell from the parts breakdown what that bottom bushing is built like

I bet there are not many that have played with a 4 hp from 88.

what happened to this thing that caused you to take it apart?

[Auminer_]

what happened to this thing that caused you to take it apart?

Guess it would be a good place to start. I bought this with the drive shaft buggered up by the PO. The pinion gear on this model 4LJ (1986 not '88) is held in place with a cir-clip rather than a nut as in the larger hp motors. The very end of the shaft that held the cir-clip in place had been partially broken off. I ordered a new drive shaft. The original shaft had jumped up when the pinion came off as told by the water pump pin going up through the metal pump housing. I can't figure out why the cir-clip came off as there is no damage to the gears nor the dogs. Case was full of oil, no water. Maybe the PO didn't get the cir-clip fully installed?? Prop even looks like normal chips/wear/use. Shear pin is a slightly bent...

[99yam40]

Maybe Rodbolt will chime in.
not sure he works on the small motors much, but he may know how the bushings and other parts hold things in position.
(what sets the clearance)

I my self do not know what could put enough upward force on the shaft to snap off the end of shaft the clip sits in and push the pin in Water pump up thru the metal housing

[rodbolt17]

let me try to find a manual for the tiny mite today.
I have not had a 4hp lower apart in about 20 yrs.
we don't see much of the tiny mites here.
mostly 150 and up with twins or triples.

[Auminer_]

I sure do appreciate you fellows looking into this for me. I work on all my own stuff and am rather mechanical, but this one defies my logic. If you need more pic's, I can get them for ya.

Dave