Prop "Hub Length" question

Hey guys,

I was under the assumption that most mercruiser drive props were interchangable. (15 spline hub)

I have a 1978 Merc 470 with a One Drive and my current prop is a "48 7958044 25P" I need to go down to a 23 or so.

I borrowed a spare 21 pitch prop from a friend this weekend to see where my RPMs were at. When I went to install it, the hub length (main prop body) on his was 7"s. Mine is 6"s. His covered all the splines on my output shaft so I could not install it.

My dad has a Trophy Plus 4 blade on his 200 V6 Merc OB and his hub length is 7"s as well.

When I am looking for props, how do I determine what the hub length is? I do not remember seeing this information in my research.

Thanks for the help,

-Eli

Re: Prop "Hub Length" question

Your prop is what's refered to as an "old style" Merc- 1983 and older.
If you switch to a new style prop, you'll need to use a thinner thrust washer.
Take a look at your buddy's. I'll bet it's half as thick as yours.
Hub length will change with different syles of props. No need to worry as long as the prop is seated and your castle locks on the splines.

Re: Prop "Hub Length" question

Thanks for the reply.

Is there any way I can tell when I am looking at props online if it is an "old style" prop? When I search for props on iboats they have listings for the 470 through 82. I assume these would be the correct hub length right?

Also, the thrust washer would have to be REALLY thin for any splines to be exposed with the new style prop.

-Eli