Tunnel/Stinger 75...15% slip seems too much

[marchettih2o]

Question:

I have a light tunnel with a slightly modified 50 cu in stinger. I am running a 11 3/4" X 23" cleaver 3 blade. I am only getting 72 mph gps at 7200 rpm's..this calculates out to roughly 15% slip. I am surprised the slip is that high. Is my issue the small diameter I have? A good 12-12 1/2 X 23 is hard to come by it would seem. Any thoughts??? Thanks.

[John Schubert T*A*R*T]

Question:

I have a light tunnel with a slightly modified 50 cu in stinger. I am running a 11 3/4" X 23" cleaver 3 blade. I am only getting 72 mph gps at 7200 rpm's..this calculates out to roughly 15% slip. I am surprised the slip is that high. Is my issue the small diameter I have? A good 12-12 1/2 X 23 is hard to come by it would seem. Any thoughts??? Thanks.

George,

Personally, for your set up 7200 RPM's a bit high. If you were running it with a short tower on a hydro withe the right prop, 7200 would be OK. But wou definitely need to bring the RPM's down. You can try larger diameter, but same approximate diameter & a bit more pitch would have similar results.

John

[88workcar]

Are you running the nitro gearcase or the big one? That would change things a lot.

[Mark75H]

The slip factor number may also be an indication that the marked pitch is not accurate

If the boat runs the same slip factor with every prop, I'd say the slip factor is accurate. If it varies, I'd suspect the inaccuracy in the marked pitch esp if just one prop varies.


What slip factor do you get with other props?

[Billsboats]

Which case would benefit him the small one or the larger one? what r the ratios?

[Fast Fred]

[850cc racer]

we run a nitro, 1.86-1 gears. on a 13ft mono 12x23 @6500rpm thats 75mph.

the larger box is 2.4-1

smaller box is better. you can put 2.4-1 gears in the nitro

[88workcar]

The slip factor number may also be an indication that the marked pitch is not accurate

If the boat runs the same slip factor with every prop, I'd say the slip factor is accurate. If it varies, I'd suspect the inaccuracy in the marked pitch esp if just one prop varies.


What slip factor do you get with other props?

I agree, I have a prop that is stamped 26p, on the slip charts it is really a 27p

Which case would benefit him the small one or the larger one? what r the ratios?

I don't know, it would change the gear ratio that he is multiplying by is why I asked.

[sharpeye Mike]

I second that, what would be the best slip ratio for a cleaver?

[88workcar]

People tell me that my slip is wrong, don't know, don't care 6900rpm 26p 77- 78 mph. 2.0gear