Fore & Aft Play In Prop Shaft ?

[tahoejag]

What is the tolerances for fore and aft prop play on shaft? I've heard that it is supposed to move some...but how much? also the front of prop has to be in the drive unit at least 1/4" ?

 

[emoney]

Re: Fore & Aft Play In Prop Shaft ?

You might be better served asking this question in the Mercruiser I/O forum, as manufacturer's specs will differ based on the outdrive, I'd think. As for the latter question, not sure what you're asking?

 

[tahoejag]

Re: Fore & Aft Play In Prop Shaft ?

When u put your prop on and slide it down the prop shaft, the front of the prop hub slide into the lower unit so far....heard that the hub is supposed to be at least 1/4" inside the lower gear unit.

 

[Texasmark]

Re: Fore & Aft Play In Prop Shaft ?

Shift your engine into F gear; power off. Grasp the prop and carefully turn it cw (looking forward) and as you do, watch the position of the prop with respect to the gear case right in front of it. You should notice the prop move out and back in a saw tooth fashion. This is the overrun clutch at work. When decelerating, where the prop is turning faster than the engine if the prop couldn't disconnect from the engine, as soon as you cut the throttle, you would wind up with a mouth full of windshield. This allows for a gradual speed reduction. R gear is not that way, it has cogs which lock but you don't need the clutch because you can't back up all that fast due to taking water over the transom.

1/4" is just fine and if the engine is in N, you can just grasp the prop and push on it and it will go in against the shifting spring and back out when you release it.

If you want another reference, go to a dealer who has rigs on display and grasp the prop on a new one and note the movement.

Mark

 

[tahoejag]

Re: Fore & Aft Play In Prop Shaft ?

Gotcha...Mark, thanks for the reply, will do.

 

[theBrownskull]

Re: Fore & Aft Play In Prop Shaft ?

Mine has done that since it was new. No worry.

 

[theBrownskull]

Re: Fore & Aft Play In Prop Shaft ?

It is an Alpha unit though.

 

[Texasmark]

Re: Fore & Aft Play In Prop Shaft ?

It is an Alpha unit though.

Sooooo. You still have the windshield in the teeth thing to consider, regardless of mfgr.

Mark

 

[jevbrowser]

Re: Fore & Aft Play In Prop Shaft ?

Shift your engine into F gear; power off. Grasp the prop and carefully turn it cw (looking forward) and as you do, watch the position of the prop with respect to the gear case right in front of it. You should notice the prop move out and back in a saw tooth fashion. This is the overrun clutch at work. When decelerating, where the prop is turning faster than the engine if the prop couldn't disconnect from the engine, as soon as you cut the throttle, you would wind up with a mouth full of windshield. This allows for a gradual speed reduction. R gear is not that way, it has cogs which lock but you don't need the clutch because you can't back up all that fast due to taking water over the transom.

1/4" is just fine and if the engine is in N, you can just grasp the prop and push on it and it will go in against the shifting spring and back out when you release it.

If you want another reference, go to a dealer who has rigs on display and grasp the prop on a new one and note the movement.

Mark

Hey mark. Thanks for the info. I've heard several of your comments on some of the other threads in the eye boats forum, but I'm still a bit confused. I understand what you're saying about the sawtooth fashion and how when you decelerate the boat that the prop needs to spend freely. But here is my problem, when I put my shifter in forward my prop will not turn in either direction. At some point you have said to put the shifter in forward and then either clockwise or counterclockwise it will spin freely or click at least. Mine doesn't move at all. So what do you make of that?

 

[Texasmark]

Well maybe you don't have an overrun clutch.....according to Faszbullet some engines don't have one.....I can't imagine that but what do I know......

I am not familiar with your boat. Go to a dealer of your boat and do the test I mentioned on new boats then worry about it if different!