Play on propeller shaft

[YellowT]

Hello. The engine is a 2023 Merc 150 with a Solas prop - 105 hours on the engine, 50 hours on the prop and prop hardware. Just noticed that the prop can be shifted in and out about 1/8 - 1/4 inch on the shaft. Resting state is out, prop can be pushed in, but then moves back out and feels spring-loaded. Movement is smooth and consistent, no noise. No water in lower unit lube, no shifting problems, no indications of a spun prop or a worn thruster bearing. Prop is torqued to Merc spec.

Is the prop on this engine actually spring-loaded in some way to disengage momentarily, as when backing off the throttle? Or am I just compressing the rubber hub? This movement feels too consistent, quiet and firm to be slack from wear.

Thanks.

 

[Chris1956]

Gee, some in-out movement of the propshaft in the gearcase is normal.

However, the prop is solid. The thrust hub washers and nut when installed and tightened properly, should not allow movement on the splines.

Most Mercs have a ratcheting forward gear. This allows the prop to freewheel under sudden deceleration.

 

[racerone]

Remove prop.-----Check end play on the propshaft and report actual value.----Some aftermarket props require a different thrust washer set-up.---

 

[YellowT]

Thanks, both. Suggestions done. In and out prop movement is 1/8 inch. No side to side movement. Rubber hub looks good, the washer looks new, prop retorqued to 55 lbs. Movement unchanged. It's the shaft that's moving in and springing back out, not the prop and hardware.

Assuming that this is normal, then....

 

[Chris1956]

Yes, likely normal movement

 

[Texasmark]

The F gear in the lower unit has an "overrun clutch" built in whereby in F gear, the engine can turn slower than normal vs the prop rotation for times when you throttle down the engine and you are up to speed. Without it, you chop the RPMs, the prop follows the engine and you have this "brake" that attempts to stop your boat putting your teeth in the windshield (possibly) if you have one.

The overrun clutch basically is a sloping ramp and vertical reset....think saw blade. In the prop faster than the engine mode, the sloped portion is engaged and the prop moves in and out as it follows the slope. In prop slower that the engine mode....when you are accelerating, the vertical portion is in play and the prop is locked to the crankshaft via the drive components.

As others have said, it's working as it should.