Monster 720 build w/FPP, too much HP for this prop

[Sebastian Bluecrew]

Matt, chime in..
This is my current setup..
1997 Seadoo SP with 720, Factory Performance pipe and ECWI Microtouch, WSM piston kit .75mm overbore, dual 44mm Super BN jetted at 132.5 low/120 high @ 20PSI pop-off,Mounted on Westcoast intake manifold, Ocean pro vortex filters, 150psi x2 , Solas X-Prop 17/24, Worx Intake grate, Sunoco GT260 100 Octane race gas cut with 93 octane about 50/50 blend. pre-mix Klotz Super techniplate oil with a bit of Klotz BeNOL mixed in to it and I also run a couple ounces of Klotz Nitro (Nitropropane/nitromethanol)

This thing is a total monster... I'm guessing I am over 50mph, and she is just nasty.. Pulls so hard, but it seems I have so much more horsepower left over even with this prop.. the 16/21 Solas I just removed would tach out at just less than 3/4 throttle at like 43MPH so I bought this steep prop.. It still hits the rev limiter at about 7/8 throttle but my top end went through the roof, the pump is hooked up, i just have to keep from holding it wide open because she bounces off the limiter... Could I still have more horsepower than prop? Its new jet pump bearings, new wear ring, new neoprene seal, and new carbon seal.. Guy at Impros told me to get rid of the carbon seal is it total garbage, and go back to the bearing carrier to avoid sucking any air to cause cavitation.. But I know some people out here will disagree.. Impros is hesitant to pitch this if I send it to him because he said first i need to find out why it is hitting rev limiter when I'm topped out ,when it normally takes $10,000 to build a motor that will even turn a 17/24 xprop.. When I had the 16/21 Solas on it, I couldnt get past 43mph and I could never hold it wide open or it would just smack the rev limiter, now I have to be well over 50mph, but havent clocked it.. I know it is much faster because I have to hold on for dear life... What would you do? Matt B, (or anyone) what did it take you to turn a 17/24 Xprop and what would it take to max out an impeller??? If the answer is "You are cavitating" then what will happen if I resolve the cavitation? Will I gain even MORE top end? Because it sure is scary on an SP at this speed.. Or Do I need more prop? I want more top end, I dont want to have to think and listen on where to hold the throttle so i dont lay on the limiter for the entire time while I am racing someone at 55mph...

 

[glsmohio]

just a few questions, If i remember on this ski it doesn't have vts. is the ski hopping out of the water? Every time it hops out of the water it will hit the rev limiter. I have this same ski that i built and im running 56 to 57. it will out run a stock 96 seadoo xp (with the 787 in it). I really think you got to much carb for this set up but thats another story. Also your not running any trim tabs on that sp ( at least from your one youtube video i watched)

 

[mikidymac]

You are going to have to find out what rpm you are turning at WOT. What is your rev limiter set at?

Also you should be way over 50 mph, more like 55-56.

A 720 with your mods should be about like a 1996 XP with the 787 and top out at about 56 mph.

 

[glsmohio]

yep nice info, on mine i turn right about 7000 to 7100 rpms

 

[Sebastian Bluecrew]

just a few questions, If i remember on this ski it doesn't have vts. is the ski hopping out of the water? Every time it hops out of the water it will hit the rev limiter. I have this same ski that i built and im running 56 to 57. it will out run a stock 96 seadoo xp (with the 787 in it). I really think you got to much carb for this set up but thats another story. Also your not running any trim tabs on that sp ( at least from your one youtube video i watched)

I have trim tabs I just havent put them on yet.. have to drill and tap some holes..

 

[Sebastian Bluecrew]

I think this rev limiter should be around 7250?? Is that what the Microtouch is set at? It is the non-programmable..

 

[glsmohio]

find out what rmps your turning then report back

 

[Matt Braley]

Shouldn't have to drill and tap holes for trim tabs. I agree that 17/24 is steep, I have a couple like that I would sell cheap because it's too much for most situations. First get GPS speed and RPM on flat water like they were saying. Then see at what rpm that your limiter kicks in. If you really do have the extra power you could get smaller nozzles and that would lower rpm and increase speed.

Look up underneath with a flashlight from the intake grate area and make sure the neoprene seal did not slip out on you. It sounds like you might have a slight air leak and just can't quite get all the "rubber to the road".

 

[POPPS]

This suggestion may contradict the use of trim tabs on the threads, we had them, then one cracked, and the repair (aluminum weld ), was going to be costly, so, I put the stock ones back on, and my son, the rider had no knowledge that the tabs were changed. If your vts is working, you should be fine.

 

[JeremyD615]

A decent inductive tach with a max rpm recap function runs less than $30 on Amazon. If you don’t already have one, I’d highly recommend picking one up, as it makes troubleshooting a whole lot easier...