Thread: RPM vs. Speed question
07-20-2006, 09:00 PM #1
RPM vs. Speed question
I spun my Island Racing balaced Solas 14/20 today at 7160 RPMs but was only running 63.4 mph in very light chop? What gives?? i got toasted by not one but 2 Ultra 150's, but i did kill 2 RXP's!!!!!! LOL Anyways, back on topic...why am I turning good RPM's but not top end? MY pump shoe may be sitting a bit low, could it make that much of a difference though?
07-20-2006, 09:12 PM #2
- Join Date
- Feb 2006
- Birmingham AL
yes it will have an effect on your top speed.
07-20-2006, 09:14 PM #3
- Join Date
- Apr 2006
- South MS
I've heard if the shoe is hanging low it could take off several mph. That prop and rpm you should be at least 69mph+. You sure your ski's not dragging an anchor or something? J/K Seriously, have you tried a different gps? Because most rxp's go 67mph+ or more.
07-20-2006, 09:15 PM #4
I know it will effect it a litle bit, but not that much will it? SHouldnt i be at or around 70 with that prop at that rpm?
07-20-2006, 09:15 PM #5
Check your pump shoe.
BTW,how did you beat 2 RXP's and lose to a Ultra 150?You should be running alot faster spinning a 14/20 @ 7160 rpm.Have you compared your GPS with your cars speedo?
07-20-2006, 09:17 PM #6
Stock RXP's but heavily modified Ulta 150's....these 150's run low 70-71
07-21-2006, 04:09 AM #7
I would tell you to lose weight, but you don't have that problem! The pump show is hanging down 1/4 to 3/8s of an inch. That is part of the problem, but not all of it. You don't have cavitation, so maybe consider an 800 grate.....
07-21-2006, 07:35 AM #8
if your pump shoe is down only 30 thousands it can rob you of 5 to 7 mph.. do you have water in your hull ? the pump shoe pulls down allowing water intrusion in to the hull due to the area around bolt cracking out...here is what it looks like.....yamaha has a recall on the 03 model.
07-21-2006, 07:38 AM #9
Nah, i fixed the cracking problem a while back with some "top secret" hull reinforcement!! Aluminum and fiberglass...and thats all im saying. Me and "Mr. Bill" are thinking the shoe is sitting too low, i just wanted others opinions before i take the damn shoe off and reseal it again!!
07-21-2006, 11:08 AM #10
Mine is pulling 7200 and im only going 67ish I think my pump is hanging low, Im going to pull the pump off this weekend (if I can get it off) and remove the piece of felt and this time im going to use the weight of the ski on a jack to help hold the pump snug against the hull.
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