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lots more power no more speed

You will unlesh your true h.p. with a good set of headers. with the work you have done your motor has to flow at both ends.
 
Yah ok guys, you got way over my head now. I was there for the whole engine build and i didn't hear any talk like that, so i can asume they built me a car motor instead of a boat motor. I have one off my boating buddies from oso going to fix me up in a couple of weeks. He builds lots of motors for fountains,profiles, and baja's, and makes them do unheard of speeds. so he is gonna fix me up. Thanks for all the input, its good to be back on this site....
 
DISTURBED.. You got the right idea now.. Go to a high performance boat motor guy. If your motor guy put the cam in 4* advanced from grind specs I bet it realy sounds like it romps at idle and revs quick with no load. The problem is that you could be killing your upper rev power. With the cam you have you might even need to go retarded a few degrees. It would be great if you only need to degree in the cam and advance your ignition to fix your problem. A good builder knows the flip combinations on +/- gear sets to get you right where you need to be. Set up wrong you might not even be making the power you had before all the work.

If you had a day or so to play on a dyno you could realy get it dialed in and know exactly what you got.
A day or so on a dyno.... Do you see dancing $$$$$$$$'s in your dreams...
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Seems like you got the right stuff. You just got to get it to work.. Good luck..
 
I HEAR THIS EVERYDAY....I PUT IN A KILLER CAM,BIG HEADS,BIG CFM CARB AND IT RUNS SLIGHTLY BETTER THAN STOCK.....THE REASON IS YOU MOVED THE HP BAND WAY UP AND NOW YOU HAVE TO REV IT A WHOLE BUNCH HIGHER TO SEE THAT EXTRA POWER YOU MADE..AND YOU HAVE TO GO DOWN IN PITCH TO REV THE ENGINE MORE AND WHEN YOU GO DOWN IN PITCH YOU LOSE SPEED... YOU NEED TORQUE AND IF I HAD TO GUESS I WOULD SAY YOUR ENGINE WHEN IT WAS STOCK HAD MORE TORQUE THAN IT DOES NOW.... ALSO BIG CAMS AND BIG HEADS AND BIG CARBS ARE FOR BIG MOTORS....TONE DOWN THE CAM A LITTLE.. OVAL PORT HEADS (UNLESS OVER 540 INCHES)CARB IS WAY BIG! 750 CFM IS MORE THAN ENOUGH...TIMING TOTAL 32 DEGREES.425 HP WITH GOOD TORQUE SHOULD BE 68-70 IN A 242 CONVINCOR..SWINGIN A 24 4 BLADE 5200 RPM..YOU CAN FIGURE A 242 OR 253 AT 17% SLIP FOR SPEED FIGURES IT TAKES A REAL GOOD CAT TO SEE 10%... OUR 253 WAS OVER 20% WITH 1.50 RATIO 6000 RPM 36 PITCH 4 BLADE (108)

BIGGER IS NOT ALWAY'S BETTER...KEEP IT CONSERVATIVE
 
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by boatn70:
just for the record, convincor242 said his boat ran about 78 tops gps, 74-76 all day with passengers and cooler in boat. then last time he pulled the motor he said it dynoed at 600 hp and some change. so 600 will get to 78, i dont think that 425 will see 75ish but i may be wrong. i would say you should be at 70!!!

dont get discouraged here disturbed, lotsa advice, try some of the theories, i think the cam advance and timing may be a big issue.

some cam grinders will grind a 4* advance in the cam and maybe you added another 4*?? i cant say for sure but check into that....ive heard such things as your old motor(7.4) you can just advance timing and see noticable HP gains!!!! timing is important!

keep me posted on this, i still dont have my motor together!! ill let you know how it runs in the spring, maybe we can trade out some props to test and get the right one!!
thanks
kevin <HR></BLOCKQUOTE>

boatn70,
I'm just saying that if he has 425hp at the prop, he should be doing 75mph in a 242. I have a 270 w/ 496HO - 425hp at prop and I run 72mph on GPS...Unless for some strance reason, the 270 is a faster design than the 242???

-Craig
 
your running good craig, every boat is a little different. i didnt mean to step on any toes here! im just repeating what ive seen to date(im definately not a pro at this!!)
Jason Kunkle does seem to agree though.

Jason, ive calculated my 242 with a 23 mirage plus at 4600 rpm running 58.6 gps with 1.5 bravo.
thats only 13%.....

then with a 22 pitch 4 blade Q4 it ran 56.6 at 4650ish, call it 4600.
thats only about 12%......

am i doing something wrong here or could i be getting those numbers because the boat is underpowered with the 300hp 7.4??

thanks
kevin
 
Jason, your numbers on the 242 only add up to about 66mph, i think like you said the 242with 425hp should be knocking on 70s door!

youve got a heck of lot more knowledge than i do so please speak up here. im just trying to learn a little bit more!!
thanks again
kevin
 
70,
the calculations on your 242 are right on, mine had 300hp and ran on its best day 59gps@4750 with a 22 bravo 4 blade, and ran the same number with a 23 mirage plus 3 blade, i just lost hole shot. To let you guys know, i am going to run the motor i have until about april. and then put in a hp 500, i found used for 4000.00 only 75 hours. merc mechanic has gone through , said its in great shape. Screw all this trying to figure my motor out. Its simple guy built me a car motor for a boat.....
 
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by boatn70:
your running good craig, every boat is a little different. i didnt mean to step on any toes here! im just repeating what ive seen to date(im definately not a pro at this!!)
Jason Kunkle does seem to agree though.

Jason, ive calculated my 242 with a 23 mirage plus at 4600 rpm running 58.6 gps with 1.5 bravo.
thats only 13%.....

then with a 22 pitch 4 blade Q4 it ran 56.6 at 4650ish, call it 4600.
thats only about 12%......

am i doing something wrong here or could i be getting those numbers because the boat is underpowered with the 300hp 7.4??

thanks
kevin <HR></BLOCKQUOTE>

I didn't expect my boat to run like it does. Maybe that 1.65 gear ratio that I have is the key...in a 270 anyway. 72mph is about the best I expect, though with 496/425hp power.

Also, the older 242, is really close to 26' long, isn't it. My 270 is actaully the old 259. These boats are probably pretty comparable?? Not sure. Anyone?

-Craig
 
yes, i believe later it was called the 260 including the platform.

maybe it is the gearing, i hope mine runs well too!!!

kevin
 
SORRY GUYS!
CRAIG YOUR RIGHT...YOUR BOAT IS AT 13% SLIP...I GUESS I SHOULD HAVE BEEN A LITTLE MORE CLEAR...I WAS TALKING ABOUT SPEEDS IN THE 85 MPH PLUS RANGE....SLIP GOES UP FASTER YOU GO IN A V-BOTTOM.
 
thanks Jason,
dont get me wrong, im not doubting what you were saying, ive just been spending some time lately analyzing my situation too!!!

thanks for all your input!!!

kevin
 
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