MORE SPEED

[BUFORD]

WHAT I HAVE IS A 1972 11' CHECKMATE PLAYMATE WITH<br />A 25HP NISSAN OUTBOARD.I INSTALLED A CMC POWER TRIM/TILT ON IT AND I HAVE A 15 PITCH BALLISTIC<br />PROP ON IT.I'M RUNNING 6000 RPM'S WITH THE BALLISTIC PROP ON IT NOW AND MY SPEEDOMETER SAY'S 42 MPH.WHAT I NEED TO KNOW IS HOW TO GET MORE <br />SPEED OUT OF MY BOAT BECAUSE THE OTHER BOATS<br />ON THIS LAKE ARE RUNNING 47 TO 55 MPH WITH A 25 HP<br />MOTOR AND I WOULD LIKE TO KEEP UP WITH THEM.

 

[Chinewalker]

Re: MORE SPEED

Chances are the "other guys" have happy speedometers. Either that, or their motors are nothing more than 35s with 25hp hoods. 42mph with a 25hp is already doing VERY good. I would say that your current set-up is pretty well tapped out, although you might have a little bit of wiggle room if you can find a taller prop - maybe another inch or two of pitch.<br /> Are you and your lake buddies running head to head or are these speeds coming out in conversation late at night after a six-pack? 55mph with a stock 25hp and service lower unit isn't likely. I'm getting about about 60mph with a made-for-racing Mercury 25SS on a made-for-racing hydroplane, so service motors in the same horsepower range approaching that speed sounds fishy...<br />- Scott

 

[BUFORD]

Re: MORE SPEED

THEY HAVE TO BE RUNNING THOSE SPEEDS BECAUSE I <br />CAN'T KEEP UP WITH THEM.WHEN YOU SAY A TALLER PROP<br />DO YOU MEAN LESS PITCH LIKE A 13 PITCH? THE ONE<br />GUY THAT IS RUNNING 55MPH HE HAS A MINI VOODOO AND HE SAY'S HE SOMETIMES RUNS RACING FUEL THOUGH HIS OUTBOARD DO YOU THINK THAT WOULD GIVE MORE SPEED?

 

[ivar]

Re: MORE SPEED

Taller prop = more pitch. <br />How high is your cavitation plate in relation to the hull? Raising the engine might give you a couple more mph if its mounted too low.<br />Running racing fuel by itself doesn't make more power , but it allows higher compression (which makes more power) without the engine blowing up. <br /><br />Oh and BTW , turn off your Caps Lock key, hard to read.

 

[Chinewalker]

Re: MORE SPEED

Hi Bufurd,<br /> Unless your motor is built to handle racing fuel (.ie Cam2, etc.), you can actually DECREASE performance by running it. Racing fuels are higher octane and in order to take advantage of that you'd have to have a much higher compression ratio.<br /><br /> Incidently, you might want to do a search on theoretical speed here on the board, plug in your gear ratio, RPM, prop pitch, etc. and get a more accurate speed expectation. I'm not familiar with the motor you're running, but if it's running approximately a 2:1 gear ratio, and for instance, a 15-inch prop, you should be running approx. 42.6 mph with zero slip. Since no propeller has zero slip, your speed would be significantly less than that. Do you know your gear ratio? You can figure it out with a degree wheel on the propeller while you spin the flywheel one complete revolution. The guys running well over 50 MUST have something else going on, as the cannot be going that fast with stock style service motors...<br />- Scott

 

[BUFORD]

Re: MORE SPEED

the cavitation plate is even with the bottom of<br />the hull and the gear ratio is 1.92:1.what i'm <br />going to do is get a gps unit to make sure my <br />speedometer is correct and thanks for all the info.