SN 200 Pro for High Altitude

[qstufflebeam]

Any one have any suggestions for propping a SN 200 with a 409 at 6500 ft? I am currently running the 422. The boat is a dog out of the hole. When I bought the boat I upgraded the motor to avoid the issues at higher elevations. Maybe I made the wrong choice in engine size. I wonder how bad the 343 would be at this elevation.

[DanielC]

Engines lose 3 percent of their horsepower per 1000 feet of altitude. At your altitude, either engine is down about 20 percent. There is also the issue of the Ski Nautique 200 not having the same performance as the Ski Nautique 196.

[dski]

While not a 200, I have a 206 and had to prop down due to elevation. What is your RPM at WOT?

I have a 2004 206 with the 330. The pull out at 4600ft was a bit soft for my liking so I went to the 1868 and had them add some cup to it. The 422 was giving me about 4650 RPM WOT and the 1868 was at 5100 RPM stock. I sent the ACME 1868 back and they added some cup to the prop (.50) and now it pulls almost exactly 5000 RPM and the hole shot is fantastic. Top speed went from 44 down to 42. Adds about 300-350 RPM at ski speeds. Super happy with it.

[Rick]

At 6500 feet (Lake Tahoe) we always pitched down 2 sizes. If you are running a 14 X 15.5 you would go to a 14 X 13.5.

[TRBenj]

Like the question was asked before, how many RPM's are you turning at WOT with the 422 right now? That would give us an indication of how far you can prop down and still get respectable top end (ie, keep the boat near, but not up against the 5600rpm rev limiter).

[qstufflebeam]

Does the RPM number at WOT need to be taken at 6500 elevation? The reason I ask is I only use the boat on that lake four times a year. Most of my skiing is done at 4500 feet.

[dski]

To get maximum performance at that altitude, yes. If you are mostly using it at 4500 feet, you should do the WOT test there. My guess is that you will benefit from the 1868 even at 4500.

I would give it a WOT test at 4500 and tune for that.

[TRBenj]

To get maximum performance at that altitude, yes. If you are mostly using it at 4500 feet, you should do the WOT test there. I would give it a WOT test at 4500 and tune for that.

I agree.

I think its too early to speculate which prop would work best for this particular boat at this particular altitude... there are many props available that would help dial in the RPM's.