Hey Guy's
I Just Put A 525 Efi Merc Racing Motor In My H2x. I Have Talked With People Over The Years That Claim A Radar Or Gps Speed Of 70 Mph With A 496 H.o. Stock. I Am Trying Different Props But So Far With A 26p Bravo I Am Getting 71 Mph At 4600 Rpm. I Know I Am Not In The Sweet Spot Which I Have Been Told Is About 5150 Rpm. I Will Try A Lab 25p Bravo But That Will Get Me Maybe 5000 Rpm With Luck. Droping Down From A 25p The Speed Drops Down Quite A Bit. I Am Already Disapointed At The Top Speed Of Just Over 70 Mph On Gps. Also At That Speed It Starts To Chine Walk From Side To Side. Has Anybody Got Any Idea Why This Boat Isnt Doing Close To 80 Mph.

Thanks,
Str0ker96

check for codes???with computer or scanner

My uncle had one with a 496ho and it would gps 70 with a 28 lab.

Speed does not come that easy, about 1 MPH per 10HP. I think you are prettey close to normal. I have a 24 with 489 Stroker 500HP, 69 GPS @ 4900 RPM, 25P Mirage Labbed. I too am a little over proped my target is 5400RPM. You really need external steering if you get chine walk above 70. So far mine is rock solid at top speed. For optimum setup a -2 shortie or -3 raised ext box would really help. That is on my list also.

Surprised you are having the chine walk issue? My H2X has 502 mpi and has GPSed 75 before and never chine walked.

IMO, your motor isn't turning up like it should. A 525 should spin that wheel right on up.
Timing?
fuel issue?

Look at it this way. If a 425 hp 496 goes 70, wouldn't you think that 100 more hp should be uper 70s?

What about your setup and drive height? Drive could be too deep in the water. May need a shorty lower unit and/or have the X dimension raised.

HEY GUYS,
THANKS FOR ALL YOUR INSIGHTS TO MY PROBLEM. THE MOTOR IS NOT THROWING ANY CODES FROM THE ECM. I DO HAVE HYD. STEERING BUT I WILL CHECK FOR PLAY IN THE DRIVE UNIT. MY TEC SAYS TO DRIVE THROUGH IT OR SAW THE WHEEL TO SETTLE IT DOWN. I DONT LIKE THAT IDEA I THINK THERE IS A PROBLEM HERE AND I WILL FIND IT! YOUR UNCLE MOST HAVE NEEDED A LARGE BODY OF WATER TO SPIN UP A 28P, WAS IT A STOCK 502? I CAN IMAGINE IT MUST HAVE TAKE QUITE AWHILE TO GET ON PLANE, BOTTOM LINE HE GOT TO 70. I AM LOOKING FOR ALL AROUND PERFORMANCE NOT JUST THE TOP LINE. SO YOU GUYS HAVE A GREAT WEEKEND ON THE WATER. I WILL BE AT PARKER STRIP, LAKE HAVASU WITH KNOW BOAT. WE ARE TAKING OR JET SKIS AND THEY WILL DO 70 WITH NO CHINE WALK.

THANKS AGAIN,
STR0KER

My uncle's boat had a 496ho. Yes he did have to ease it onto plane. Like i said though it was labbed and it was for top end only. The boat was ran here at Cumberland. I believe it was an 05, was a fun boat. Have a great weekend, wish i was boating this weekend

man that motor should turn a 28b1 and yes you have to saw the steering, but you not be getting chinewalk at that speed with add on steering and if its full hyd steering to the dash that makes no sense sorry to hear this. maybe at the end of the season if its still messed up pull the motor and have it dynoed it should be 545 to 560hp. right now it sounds like your over trimming to get to 70 which causes the walk. after you get it figured out a short will help more for the four blade. and add full hyd steering to the helm if you still have cables going up there. once set up that should be a 80mph boat. ART