Surface Drive Prop Rule
 

Is there any rule for a surface drive in terms of 200 rpm per pitch change. I am running 16 1/2 X 24 4 blades. At 0 trim or neutral trim i am @5700. The motors stop making power at 4900. I am going to try 30 pitch 3 blades. i have talked to a couple people on this and everyone said u gotta try them to figure it out. BTW 311 Formula KAAMA drive 1.54 trans 1.1 drive with 409 HP

OK prop tested sunday.

17x30 3 blade 63 @5200 anybody have any suggestions?

The set up you got has 24% slip.
Something is wrong ?!

I think 3 blades are not good for ya. $ blades in the right size is what you need.

If your engines turn 5200 RPM ,with a 26 pitch prop and a 1:154 gear ratio the boat should run 73.2 MPH on GPS.

That would be the ideal slip # .
My guess is 18 X 26 4 blades ??????? Maybe 27's ???????

Thanks maybe that is something to look at. also i was just informed that these boats need alot of trim to free up. i have yet to run max trim.

daredevil, if you could, same basic deal but a little diff. 5400 rpm---1:54 trans gear ratio---18% overdrive/drive ratio and a 17x23 4-blade wheel, approx.speed ? thanks in advance ! ps: ya & 3-blades don't work well.



CORRECTION

67.20 BIG Daddy :ernaehrung004:

I've got an old Cigarette Flat Deck with Arneson Surface Drives, and the general rule of 200 rpms per inch of pitch applies but diameter, rake angle, and number of blades can't change also.

My boat tends to like bigger diameter, many blades, and high rake angles.

Kris Vogt

I forgot to post my new numbers but it seems still too much slip. 17 x 29 4 blades again at neutral trim.

67.9 @4800

if i trim up all the way i think i can turn them 5100 BUT i also think it will prolly slip more.

I am also thinking more diameter less pitch like a 18x 27 or 28 would be perfect!!!

I think thats with i questimated ?! LOL ( the prop size)

I would also think a 18X28 , and go from there .

But the slip # came down to 12% which is not bad at all !

slip
 

Bill, how are ya doin ? Thanks for the est. same set up as car-biz except kamma drive 18% over w/ 1:54 trans 17x23 prop 33-Sutphen seen 80+ what are u-fig. on the slip and @ say 5600 what is your est. mph daredevel jump in if u-wish thanks guys ! :drink: ps: ya ya it's a SKATER NATION :ernaehrung004: