Mainship 390 prop mount?

[Pluto]

Can someone verify If the prop uses a keyway or is it a tapered shaft? I’m trying to figure something out and the boat is far away.

[Bacchus]

Should be both.
Here's a good how to
https://marinehowto.com/lap-fitting-a-propeller/

[Pluto]

Thanks B. My problem is the prop is spinning freely on the shaft. My diver thinks the keyway failed but doesn’t want to remove the propeller without having a new keyway. Anyone know what size the keyway is?

[jleonard]

Originally Posted by Pluto

Thanks B. My problem is the prop is spinning freely on the shaft. My diver thinks the keyway failed but doesn’t want to remove the propeller without having a new keyway. Anyone know what size the keyway is?

The "keyway" is already machined into both the shaft and the prop.
The "key" is what likely sheared.
If you know the shaft diameter it should be a standard size for that shaft.
You should be able to find that out via google search or by asking a prop shop.

You might want to know why it failed. Did you hit something?

[Pluto]

A prop shop was able to help me out. Thanks gents.

[Shrew]

I would have the shaft inspected. I had to replace my shaft because the key was badly malformed and the keyway was wallowed out. I suspect it's caused by not waiting for the prop to slow before knocking it from neutral into gear. Such as going straight from FWD to REV, vice versa, or not waiting long enough.

Just my .02. I'd be concerned about the state of the keyway on the prop and shaft.