How long to reach top speed

[Fitz]

Bgreen - that's the only holeshot video I had on hand, but I'll try to do a more extensive one this season. Can't wait for spring launch.

[bgreene]

My V21 may hit 100 mph, maybe more off a cliff, but I'm conservative and don't want to push it that hard...

[garbubba]

I'm at a loss here....

13.75x17 ss prop, 13 7/8x15 aluminum prop, 13.75x13 ss prop

You say all three of these props gave you the same RPM's at WOT? Comments about aluminum being different than SS notwithstanding the two stainless props are 4 inches of pitch different, they should give you way different RPM's at speed.


The tach sure seems suspect, if not something is surely wrong.

[THEFERMANATOR]

Originally Posted by garbubba

I'm at a loss here....

13.75x17 ss prop, 13 7/8x15 aluminum prop, 13.75x13 ss prop

You say all three of these props gave you the same RPM's at WOT? Comments about aluminum being different than SS notwithstanding the two stainless props are 4 inches of pitch different, they should give you way different RPM's at speed.


The tach sure seems suspect, if not something is surely wrong.

Not always. 15 pitch doesn't equal x rpm and y speed for every prop. Some basic props can run say 5200 in a 17 pitch at 45 mph while a different style 13 pitch could turn the same 5200 at 42 or 43. Pitch is just one meadurement when it comes to props. Some props also have what we refer to as progressive pitch where the pitch varies across the blade, or you can have one with alot of cup in it, larger diameter, different hub, and so on.

[Destroyer]

Also, along with everything that TheFermanator just said, don't forget that different materials will also effect engine RPM's. You mentioned both Aluminum and Stainless Steel props.. Under load, while being spun against the resistance of the water, they both will flex, but at different rates. The aluminum more so than the SS. The amount of that flex also effects the final RPM's vs SOW of the boat.

[THEFERMANATOR]

And don't forget number of blades and prop slip. We went from 21 pitch vengence props on the neighbors boat to 18 pitch 4 blade michigan wheels(both stainless). The boat runs nearly the same top speeds, turns slightly less cruise rpm's at higher speeds, jumps on plane instead of just looking at the sky wishing it could get on plane(had have everybody move forward, trim both drives in, and run the tabs down all the way to plane out before), and runs 100 rpm's lower at wot. The searay 250 I did a few years back had similiar results. Went from a 17 pitch vengence to a 16 pitch mirage style, got it off the limiter, planed better, and ran alot faster.