Sanding a lower unit for speed
#42
Registered

Joined: Oct 2007
Posts: 1,465
Likes: 210
From: Grand Haven, MI
I sanded mine down last winter. They discolor after two or there times out but clean very easily with a scotch bright pad and soap and water. no paint on the lower to fall off and I think they look better
#44
Registered

Joined: Mar 2008
Posts: 3,613
Likes: 375
From: Traverse City MI
Yeah WCM is for sure the place to go but would be nice to know a little more about "blue printing" the lower. Do they sharpen the leading edge? Trailing edge? Bullet? Thin the skeg? Obviously they "true" it and make sure its stright. Sanding strokes front to back? What grit? etc. There are a lot of guys on here that like to build not buy. Its half the fun, especially if you are on a budget.
#45
Registered

Joined: Jul 2007
Posts: 3,648
Likes: 32
From: Oneida Lake NY
Yeah WCM is for sure the place to go but would be nice to know a little more about "blue printing" the lower. Do they sharpen the leading edge? Trailing edge? Bullet? Thin the skeg? Obviously they "true" it and make sure its stright. Sanding strokes front to back? What grit? etc. There are a lot of guys on here that like to build not buy. Its half the fun, especially if you are on a budget.
Amazes me how smart most people in the sport are about engines, and how dumb most of us are about hydro dynamics.
#46
Registered
Joined: Apr 2004
Posts: 1,268
Likes: 239
From: Michigan
I know most everyone understands the princpal but originaly we "Massaged" Not "blueprinted" the lowers to gain cleaner water to the small hub props to utilize all of the blade as possable outboard style cleavers, In my opinnion to effectively accomplish this with a bravo one needs to lengthen the bullet much further out than the pre-formed nosecones do. It is a ratio of diameter to length. As we all know this is really make no difference till about 80 mph and above on Vs and mid 90s on most cats.
Last edited by abones; 02-02-2013 at 07:23 PM.
#48
I just added a Hydromotive nose cone to my XR lower. It's also straightened, sharpened and a bit thinned.
I also got rid of the lower intake and modified the side intakes to make it work with the prop shafdt depth I'm at (3-1/2")
I'm going to leave it like this with no paint until l have tested.
It's wet sanded just like the bottom to a certain fine grit that according to a VERY reputable European boat designer works the best.

I also got rid of the lower intake and modified the side intakes to make it work with the prop shafdt depth I'm at (3-1/2")
I'm going to leave it like this with no paint until l have tested.
It's wet sanded just like the bottom to a certain fine grit that according to a VERY reputable European boat designer works the best.

#50
Registered
Joined: Sep 2007
Posts: 2,571
Likes: 0
From: Gaylord, Mi




Did it help the bottom of the hull? Always wanted to do the bottom of my hull.