Acme 422 on 01' Air Nautique

[pdxCC]

Hey PN members. My 01' Air has an acme 422 and I need some help with speed vs. rpm for slalom. For perfectpass, what rpm is the best setting for 28, 32 & 34mph?

I dont trust my paddlewheel or gauges for skiing on the boat.

Cheers!
Brett

[Lewy2001]

Brett I have some prop testing numbers. Mine is a 98 Sport which has the same hull as your 01 Air. Not all the figures you require but might help.
Conditions 26C(79F) No wind.
98 Sport GT40 full tank of fuel driver 88kg(195lbs) and 30kg(66lbs)dog in bow walk through.

GPS PP Stargazer readings.

ACME 422 12.5 X 15.5 OJ 13 X 16 Legend (Original)

2000rpm 14.5 mph 2000rpm 14.1 mph
3000rpm 29.1 mph 3000rpm 28.0 mph
4000rpm 37.5 mph 4000rpm 36.5 mph
4500rpm 40.3 mph 4500rpm 39.8 mph
4940rpm 42.0 mph 4970rpm 42.7 mph

[HS]

Wow, I'd have expected higher speed numbers with the 16" pitch, but I guess it shows how the diameter and pitch produces greater load on the engine.

[TRBenj]

Wow, I'd have expected higher speed numbers with the 16" pitch, but I guess it shows how the diameter and pitch produces greater load on the engine.

No, what I suspect youre seeing is the effect on top speed when you have a slow (nose planted) hull!

If you want to verify your speed, then get a GPS and set your speedos accordingly. Trying to correlate your boat's performance with another is going to be a total crapshoot. Hulls, props and ambient conditions (water temp, altitude) will cause a tremendous amount of variation- even amongst boats that are set up similarly.

[pdxCC]

Thanks for the info! I unfortunately cannot use GPS as I run on a river with a decent current. I need speed over water numbers and GPS only gives speed over land. The rpm vs speed will help validate my perfect pass paddle wheel and let me reset the Faria speedo that appears to read very fast.

Cheers!
Brett

[TRBenj]

In that case, your best bet is to run in both directions on the river at the same RPM (same speed over water) and see what the GPS says for each direction. The difference in the 2 GPS speed readings divided by 2 is the speed of the current. Use that to adjust your speedo.

Trying to get speed vs. RPM from another hull/prop combo is going to be a lot more inaccurate.

The alternative would be to dump the boat into a lake for a trial!