MerCruiser Alpha One Gen 1 – Shift Shaft Alignment Reverses Forward/Reverse Gears After Impeller Install

[culverpolley]

I’m working on a MerCruiser Alpha One Gen 1 (5.7L GM V8) and having an issue with the shift shaft after reassembling the lower unit.

I replaced the impeller and water pump assembly. When I went to reinstall the lower unit, I made sure the shift shaft was turned fully clockwise (as the manual states for forward gear), and the shift control at the helm was also in forward. The upper shift crank was facing the transom like it’s supposed to.

Here’s the problem:

• In this setup, the prop engages the driveshaft when spun counterclockwise, and spins freely clockwise.
• That means it’s in reverse, even though the shaft is turned clockwise, which is supposed to be forward.
• If I turn the shift shaft 90° counterclockwise, then the prop locks clockwise and ratchets counterclockwise — exactly what I’d expect in forward.

So it seems like the gears are completely reversed from what they’re supposed to be. The shaft only turns 90°, and only one of those positions fits the crank arm during install. But when I set it to that position, the gear behavior is flipped.

Everything I’ve read says clockwise = forward. But when I do that, I’m getting reverse. If anyone’s run into this or knows what might cause the gear behavior to reverse after impeller service, I’d appreciate the help.

Thanks.

 

[04fxdwgi25]

If you place it in forward gear (engine not running), the prop will free wheel, with clutch dog clicking loudly, when turned in clockwise direction.

Don't know if I explained it to you clearly enough, but from what I think you are saying, sounds like yours is working correctly.

 

[Bt Doctur]

look at it this way, the prop locks in a CCW direction in fwd gear and will ratchet CW with no power
the prop will turn CW when the shaft is rotated by the motor

This is fwd