HELP!! 2012 SunDeck 217 with Excessive "Propwash"!!

PegasusA300

I bought a New Hurricane Sundeck 217 in April 2012.
It has a 270hp Volvo Penta V-8 engine, I/O , Solas aluminum 14 1/4 x 17 , 3 blade prop and a 22~24 inch swim platformIt has OK hole shot and max speed is about 38-40mph at about 4950 rpm which is also wide open throttle...bimini top stowed.Here's the problem...It has OK hole shot for pulling skiers or wake boarders, but the "prop wash" off the back of the engine is incredibly huge/wide. Not a rooster tail type thing, just lots of water flying around the prop and hitting the underside of the swim platform (actually coming off the prop) and being thrown backwards for 15-20 yards. When the boat is trimmed toward "up" after getting on plane, the porpoising starts and the "turmoil" behind the boat changes very little...there is never a surge in rpm, just water flying everywhere behind the centerline of the boat. I know the technical definitions of cavitation, ventilation, and slipping and I'm not sure which apply...Local dealer tried a 4 blade 14 x 21 prop, but the hole shot was terrible, the top speed was about 34 mph and the rpm dropped to about 3400rpm WOT. So returned to the original prop... Owners manual says the MAX engine rpm is 5000.So my questions are:Will a larger diameter prop help and should it be a 3 blade or a 4 blade? I think a 15 inch prop will fit.I think ventilation or slippage is possible cause...So would a set of "SMART TABS" help the prop wash (I'm pretty sure they'll help the porpoising) by keeping the blades in the water? Do they increase of decrease the gas usage? This is a LARGE engine. The dealer said it should go 45-50 "all day long"...depending on load. There are usually only 2 of us onboard, so it might be nice to actually go a little faster but at 38mph its way slower than what I thought it would be.I really appreciate any thoughts or idea's you might have to help me solve this problem!I've owned 4 boats previous to this-2 outboard, 2 I/O, and never seen anything like this "prop wash" behind the boat!Thanks!!Mike H.

Capt_Steve

@PegasusA300 ... waiting to hear back from engineering. What is the actual model number of your Volvo? That might help them. 

cjjjdeck

Unless I'm misunderstanding, it sounds like the prop isn't deep enough in the water when you're on plane.  Do you have the Duoprop (DPS) or SX drive?  I assume you probably tried trimming down when on plane to see if there was a change in spray activity.  Did the dealer check to see if your drive has full range of motion when you operate the trim switch?

For comparison, I have the Mercruiser version of your engine (260 hp) and the Duoprop (Bravo 3) drive equivalent. My top speed is 45 mph (I hit 5,000 RPM at WOT), my hole shots are pretty quick and it produces little "spray" with an obviously heavier boat.

I have to admit, this is the first I've heard of a problem like this.

PegasusA300

Hi and thanks for the note!

The boat has a single prop...not the Duoprop. 

I always start the boat with the prop trimmed all the way down, but its almost impossible to trim very far upwards until the boat begins to porpoise. I'm not sure about the full range of motion with the trim switch. There is good hole shot...but there is an extreme amount of "cavitation" or turbulence behind the boat that appears to be water and air (4-5 feet wide and 15-20'). The other things are poor gas usage, and what I think is slow top end speed between 38-39 WOT. I hope the engineers are looking at the issues now. I have sent a couple pic's and a video for them to look at. ANY comments or suggestions you have are GREATLY appreciated!!

By the way... the prop is a 3 blade 14.25 X 17 pitch which produces 4950rpm and 38/39mph.

We tried a                         4 blade 14.25 X 21 pitch which produced 3400rpm and 34/35mph

Then we tried a                 3 blade 14.25 X 19 pitch which produced 4200rpm and 35/36mph

Thanks,

Mike