Re: 1985 50 hp merc will not turn the prop
raising the trim all the way up. Forward gear spins with compression not sure about reverse. yes i mean the prop shaft no the prop shaft does not turn in forward
Okaye the shifter works like this. The shift lever on the remote control is connected to an interconnect cable, the other end of which is connected to the engine. The outer part of the cable has a brass threaded shaft with a brass barrel on it that is also threaded and can run up and down the threads. This is how you mate the cable to the engine.
The center cable has a plastic (usually) adapter with a hole in the end and it fits the shifter post on the engine linkage. Control is accomplished by moving the engines shifter arm, hence shifting rod that goes down to the lower unit, back and forth to cycle through the 3 gears.
On the lower end of the rod is a splined shaft. It fits into the top of the shift cam which is at the very front of the LU inline with the prop shaft. The cam rotates through 3 positions and each has a different detent. Inserted into the detents is a thing called a cam follower that does just that...follows the detents in the cam and as a result has 3 different fore-aft positions.
At the rear of the cam follower and associated parts is a thing called a clutch dog. The dog is a barrel with gears cut on the front and cogs on the rear. It is locked to the prop shaft. In N it sits between the F and R gears, touching neither, hence neutral.
The drive shaft has a pinion gear on the end of it and this pinion is in constant contact with the F and R gears which spin as long as the engine crankshaft is rotating.
To shift the engine, the clutch dog is moved forward or aft by the pressure applied to it by the change in height of the cams in the shifter cam. For F gear the dog (spring loaded) moves forward and it's gears mesh with the F gears. As the cam is moved to the next position (N) it puts pressure on the dog and it moves aft slightly, disengaging with the F gears. Drive shaft turns but prop shaft doesn't.
As the cam is rotated to the final position (R) the cam is at it's highest point and exerts maximum pressure on the clutch dog pushing it to the rear and into the R gear.
That's the way it works. Now that you know, just answer the question: What isn't doing what it's supposed to do.
The first place to look is linkage between the remote cable and the shift arm in the engine. Can the remote cable position the arm in the FNR positions or is it too short on the F end and can't quite push the arm far enough to engage. If not take it off and adjust it and I have that process sitting around from the last couple of days....look at my tweets in my personal area and look for it.
Mark
