SCX prop slip
08-29-2010, 04:29 PM
#1
Registered
Thread Starter
SCX prop slip
any one switch from a bravo xr to a SCX and have more prop slip?
I went from a xr with a sc lower to a scx with a sc lower and the xr had the same ratio 1.5 and the same prop a 30 bravo 1 and my slip was 8%.Now I put on the scx with sc lower and my slip is 21% what the F is going on?
I went from a xr with a sc lower to a scx with a sc lower and the xr had the same ratio 1.5 and the same prop a 30 bravo 1 and my slip was 8%.Now I put on the scx with sc lower and my slip is 21% what the F is going on?
08-29-2010, 11:01 PM
#4
Chris
Gold Member
I have not seen prop slip increase when adding a SCX upper...but a couple of things come to mind...
1. The gears in the SCX are larger in diameter...because of this, the lower unit is moved aproximately 3/4 of an inch rearward...thereby putting the prop deeper in relationship to the water coming off the back of the boat.
2. The SCX is aproximately 42 pounds heavier than a SC or XR upper... thereby lowering the prop into the water.
These two things... along with the fact that I am not sure the gear ratio is the same in the upper of the SCX as it is in the SC/XR (I really am having a hard time wrapping my head around this exactly)... means that setup is just going to be different.
I lost aproximately 4.5 mph when I changed from my SC upper to my SCX upper. RPM dropped as well as speed with the SCX. After a lot of testing, I bought a 1" shortie, am using a 1/2 spacer, and the two uppers are within .5 mph of each other, using the same prop.
The boat has a little over 900hp, and is a v-hull. In the 100-101 mph range.
It looks like you have a cat hull... so setup is probably different.
My friend John Lamont has a 27 Nordic Thor with a NA 598, and he was exactly the same speed with his SCX upper/SC lower as he was with his XR upper/Sportsmaster lower. Johns boat does between 102 and 104 mph.
KAP just bought a 1" shortie for his Howard deck boat, and will be testing here shortly. He lost aproximately 8 mph initially from going to the SCX upper. His boat does in the 120's
This is all the info I have to date... but will keep you updated.
It sounds like the additional weight, along with the rearward movement of the prop, took you out of your sweet spot, and you are going to have to play with the setup.
Chris
P.S. it sure is nice to not be destroying uppers any more!
1. The gears in the SCX are larger in diameter...because of this, the lower unit is moved aproximately 3/4 of an inch rearward...thereby putting the prop deeper in relationship to the water coming off the back of the boat.
2. The SCX is aproximately 42 pounds heavier than a SC or XR upper... thereby lowering the prop into the water.
These two things... along with the fact that I am not sure the gear ratio is the same in the upper of the SCX as it is in the SC/XR (I really am having a hard time wrapping my head around this exactly)... means that setup is just going to be different.
I lost aproximately 4.5 mph when I changed from my SC upper to my SCX upper. RPM dropped as well as speed with the SCX. After a lot of testing, I bought a 1" shortie, am using a 1/2 spacer, and the two uppers are within .5 mph of each other, using the same prop.
The boat has a little over 900hp, and is a v-hull. In the 100-101 mph range.
It looks like you have a cat hull... so setup is probably different.
My friend John Lamont has a 27 Nordic Thor with a NA 598, and he was exactly the same speed with his SCX upper/SC lower as he was with his XR upper/Sportsmaster lower. Johns boat does between 102 and 104 mph.
KAP just bought a 1" shortie for his Howard deck boat, and will be testing here shortly. He lost aproximately 8 mph initially from going to the SCX upper. His boat does in the 120's
This is all the info I have to date... but will keep you updated.
It sounds like the additional weight, along with the rearward movement of the prop, took you out of your sweet spot, and you are going to have to play with the setup.
Chris
P.S. it sure is nice to not be destroying uppers any more!
Last edited by CB-BLR; 08-29-2010 at 11:05 PM.
