Rambunctious

does anyone have an accurate power curve for the 300hp 454 carb. I am sending in my props to be lab finished and want to know exactly where the peak power is. Merc rates them at 330hp at 4200-4600. is it at 4,600, 4,400?.

Im running 25 pitch right now at 4400 most of the time, if 4400 is actually the peak, I'll have them push the pitch to the high side to compensate for the added rpm expected from the labbing. (theoretically giving me more top speed at the same WOT rpm). If 4600 is the peak, I'll leave the pitch alone and just have them true'd up, gaining speed via the increase in rpm right to the peak Hp

thanks

MACDAD260

I have the same motor and run 4800 to 4900 with a 21" Mirage. I have tried running a 23" Mirage and a 24" Bravo. I get basically the same top speed but at 4400 rpm. The motor feels like it is lugging and working itself to death at that rpm. At 4800 it seems to run real free and sweet. I run 36 degrees of advance at 3000 rpms. Seems to help over the stock 32. I would say you should try to get your rpms up. Labbing the prop should help. What top speed are you running now? What boat? Inquiring minds want to know.

bobl

I have a torque curve(graph) on a '97 7.4L engine. It shows peak HP at 4600 RPM. It appears to really be flat from 4200-4600 though. Probably not 5-10 HP spread. Personally I'd prop it for 4600 lightly loaded. Then when you fill it up with people and beer it'll still be in it's peak range.

Rambunctious

MACDAD, I have a Formula 272 w/ twin 330's.
black/yellow/white. top speed is 64.99999 mph with my 3 year old steering. want to break that 65 mark, and then of course approach 70.....and so on.... and so on....

I see west michigan, where do you boat and with what.

bobl, thanks, I think that is what i am going to do. have the pitch "tweeked a little higher" when labbed to keep it at/around the same rpm, but gain some speed. that way, if I do anything to "free up" the engines some day, i don't need new props. One thing about these formulas, they really don't care much about load or seas, pretty consistent with rpm and top speed. But, when we are racing buddies down the west Mich lake shore, I always yell to my passengers...." keep drink'n, we need to lighten this load!!!"

tomcat

Rambunctious - See NICKSLICK's thread on "Why can't I bust 70 mph" in General Discussion for advice on that little extra something. By the way, it should be "Keep on pissing over the side..."

Madmax

Rambunctious:

Don't forget, your rev limiter will kick in somewhere over 4600. Mine hits at 4750, altho my friend has the same motor and it hits at 4900. I doubt it's a good idea to bounce it on that very much. The Mark VI carb motors are pretty tough if not overrevved, and are easy to wake up for a few more mph with just a few bolt on's.....

MACDAD260

Ram...., I have a 260 Baja. I run on "The Big Lake" about 95% of the time. Usually launch out of Holland or Grand Haven. I have run with Waterfoul a couple of times. I am upgrading to a 502 Mag this winter. My current top speed is 55MPH on GPS. I am looking to get into the low 60's. I have a 24 pitch Bravo I that will be going on when the new motor is in. You going to Crazyhorse's party?

Rambunctious

Don't know if I will make it to Crazyhorse's
but planning on the GR boat show on Wednesday night. our "SEA100 Powerboat Club" is planning to meet at the BOB for a bite before the show . wanna make it an OSO gathering? or join us yourself?. probably 6:00pm at the BOB. don't know what floor yet. working the detail. Hey. I have a RH 25p three blade for sale. gonna use the money to help pay for the labbing of my other props. will sell it very reasonable to get "the cash". Waterfoul was going to try it last year but never got around to it. think he is happy with his right now. he will be there Wednesday