want more speed

[garyoja]

1981 hammond challenger , with an alpha one r drive 1.5 ratio, stock 23 pitch cleaver , boat is 21' 2800lbs loaded , with merc 260 hp i was running 60mph gps @ 4700 rpm with this set up .



Changes for this year 330hp vortec350 , roller cam, 9.3:1 comp, balanced, rpm range of 1200 to 5200 max with comp cams xm270 hr ,650 cfm carb on edlebrock performer rpm

. Was thinking of a 26p cleaver and hoping to stay bellow 5000 rpm still .

any thoughts of what kind of speed i will get ?

 

[steelespike]

Re: want more speed

If all these changes are marine oriented a 26" prop assuming 5000 at 12% slip could produce 72 mph.
at these speeds changes aren't linear so not too predictable.
See how the 23 works out, will give you a better idea what prop is needed.Surely will over rev but will give an indication
of what prop size.

 

[gm280]

Re: want more speed

While all that sounds neat and such, do you seriously know just how fast that is in water...? :facepalm: And I can't even imagine how much gas that is going to take... :facepalm: :facepalm: But to each their own. If I were wanting that much speed in a boat, I'd build a speed boat and forget about anything else the boat could be used for... But again that's just me. Good luck with your dream machine...and be extremely safe out there...

 

[garyoja]

Re: want more speed

it is some what of a speed boat . google them neat looking boat . I fully understand what speed is like in a boat i worked for cougar in the 90s we built some 100mph plus rockets . hope to own a 23' mtr with twin out boards one day now that is my dream machine hehe .

 

[steelespike]

Re: want more speed

Yes do be careful. There is a video of reasonably fast boat trying to cross a wake at less than 60 and it catches a wave and flips sideways
stopping almost instantly.Stayed upright but the guy was busted up pretty good later scene shows him laying on the boat apparently in pain.