I'm getting to the time on my 16hp SD build to order my shaft and bearings. Was wonder which would be better for this motor or if it would really even matter. I'm leaning towards the 7/8" right now but I know the old LT ran a 3/4" shaft and didn't know if there was a reason for it.

You can get aftermarket props for a 3/4 shaft much easier and cheaper.

Check and see what size shaft the prop you will run is first.

Make sure it is a true surface piercing prop.

I was planning on running a 11X10. Hill marine has em both ways I guess its a surface piercing prop it looks different than my LT prop.

go with 3/4. alot easier to find bearings, seals and props.

Whoever took your avatar picture got a camera lens full of pintail on the collision.

3/4 all the way
cheaper for parts, lighter, more universal seals etc...(in case of breakdown)