Jet Jon cavitation HELP!

[Ccollard2004]

Hello all! Bought this boat as is. Anyone have experience with a built 650 Sea doo in a 14 foot Meyers semi V.
Half throttle 24 mph
Full throttle 24mph
Not sure if its cavitating or pushing out.
Going to smooth out bedliner, I know that can't be helping.
Haven't installed the Solas intake grate to top load it, now thinking the R&D that came on it in pic is better.
Next step is to flip it and weld a 2' spoon on it.
Am I going in the right direction? Could I just smooth out the half inch fibergalss lip in front of the intake, so it's not so abrupt? Causing turbulent water? Is this the right Forum for this? Lol
Any advice is much appreciated. Thanks!

 

[anmut]

What is on the hull of that boat, looks rough?! That could be your speed issue...

 

[Ccollard2004]

Yea its bedliner, I'm going to smooth it out or remove it completely. It has to be knocking a couple mph off the top speed. I just feel like there's a bigger issue here to figure out.

 

[anmut]

Yea its bedliner, I'm going to smooth it out or remove it completely. It has to be knocking a couple mph off the top speed. I just feel like there's a bigger issue here to figure out.

High speed in any machine is very effected by it's drag coefficient. The amount water turmoil that hull is causing would be my #1 suspect before I would dive further into the engine. Scrape that stuff off and get a nice smooth surface then retest.

 

[anmut]

Yea its bedliner, I'm going to smooth it out or remove it completely. It has to be knocking a couple mph off the top speed. I just feel like there's a bigger issue here to figure out.

A quick goog:

What difference does fouling make? - Yachting Monthly

Freshening up your anti-fouling at the start of each season is a tedious necessity, but necessity it certainly is. Chris Beeson explains why

www.yachtingmonthly.com

They're talking about growth on yacht hulls, but the theory still applies. You're looking at a 10-15% loss. That might explain your speed issue.

 

[Julian]

My boat drops from a top speed of 50 down to 35 when its covered with a NC summer fur coat (algae). That bedliner has got to go! You want super smooth!

 

[djetok]

With all the turbulence caused by the bed liner. That could also cause cavitation as well? Maybe that is causing the pump to get enough water.

 

[tdonoughue]

I was noting the lip before the intake (if I am reading the pics correctly). Is that marked for 1/2"? Seems like that alone would give you cavitation, no?

 

[Ccollard2004]

Ok thanks guys, sounds like my 5-10% loss from the bedliner was underrated. I'll start the long process of scraping and burning the stuff off and polish the hull. Also grind down that lip in front. Motor boating in Michigan is "not allowed" so not sure where I'll test it ?

 

[tdonoughue]

Bath tub?

Good luck and keep us informed!

 

[Ccollard2004]

Ok guys, pretty happy with the results!
From 24 to now 36 mph!
20 hrs of scraping bedliner and at least 10 glassing and shaping the spoon. Not your traditional shaped spoon but what a difference, it hooks up great and pulls hard to the top without all the bedliner drag. Put the R&D grate back in. Will test the Solas grate for any improvement. Only thing left would be an impeller with more pitch, even though it's got a brand new one in it. The damn thing is so much fun in the river I'll probably just leave it alone. It was a 1/2 mph faster than my buddies stock 650 jet ski. What more can I ask of it.