05-15-2010, 01:39 PM #1
- Join Date
- Aug 2008
First time out this year - thoughts?
Took the boat out first thing this a.m. Was a very cool 55F and 60F water temps and clear flat water. I am at around 5300' elevation. Boat has 24 hours now.
The top speed (NOT GPS, just the speedo) I was able to hit was around 54mph and highest rpms right around 7600. That's 2mph MORE than my best last year and 1mph less than I was ever able to hit on my '03 GTX 185HP ski. I thought I would take a hit on the top end with the change in props but apparently not. The old wear ring was in very good shape, so I don't think the change out there is much of a factor. I don't think I've ever been out on the water when it was this cold before. Good fun for an hour though.
I've got a brand new prop and wear ring. Went with a 3-blade Scat Trak 12/15 as opposed to the Solas Concord 15/20 that was in previously. Hole-shot is MUCH better than before, and I am happy with that since that was the reason I changed props.
I'm happy my 3 procedures succeeded without a hitch (change of prop, SC pulled and washers changed by Jerry, and my first oil change).
So what about my rpms - max of 7600? Am I supposed to be able to hit 8100? Would re-pitching change that? And if so, would re-pitching for higher rpms cost me "torque" in a hole-shot? Remember I'm over a mile high and normally-aspirated engines lose around 20% peak power and FI engines lose around 10% power.
Thanks in advance,
John in Colorado
05-16-2010, 09:48 PM #2
- Join Date
- Apr 2007
- Vancouver, BC
I max 7700 RPM with a 14/19 prop and with a greenwheel S/C impeller up at 3600 ft elevation with water temps about 65 F. I guess I'm getting a little more boost than you but my 14/19 is maybe a little too tall for me.
Even at sea level the same setup gets me about 7900 rpm- I need to de-pitch the prop a little.
05-17-2010, 08:26 AM #3
7600 rpm is to low for your motor. You are leaving alot of performance left on the table.
The two degree #'s on your prop are leading edge and trailing edge. The first number is the leading edge and basically thats what you tune for your hole shot. The 2nd number, or trailing edge, is what you tune for top RPM.
When you did your hole shot... what did your RPM spike to on the launch? Did you hit Rev limiter? If you spiked around 8000-8100 on the hole shot then I would leave the leading edge alone and only tweak the trailing edge. That way you're hole shot should be the same and you'll pick up some top speed.
So now the question is what to re-pitch it to? Its really hard to dial in your prop around the weather. If you re-pitch now based on your current results and in two months the water temp jumps up 20* you won't be where you want. And on the flip side... if you dial the prop in at the hottest point in the summer... you'll be smacking redline towards the end of the season in the cooler months.
Alot of the jetski guys have summer props and winter props. however, they want to be on the bleeding edge of performance at all times. If you don't want to have to worry about constant re-pitching figure out when your primary riding time will be and give yourself a little buffer.
just my .02
05-17-2010, 12:58 PM #4
- Join Date
- Aug 2008
^^ Thanks so much, Elite! This was just the info I was fishing for.
As for technique on a hole-shot, should I be going immediately WOT from a standstill? If so, I'll need to do that time a couple times and see what it does. Typically I just increase throttle rapidly rather than going instant WOT (with the old prop I had to increase throttle slowly, actually..)
I don't think I've ever hit the rev limiter on my Speedster or old 185hp GTX. So here's a dumb question. What's hitting the rev limiter like? Just stationary 8100 revs or alarm/idiot light?
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