I have a friend with a 86 Four Winns Liberator. Its a 454 Mercruiser 330 H.P. It came with a 21 pitch S.S. The boat was a slug....We went to a 15 pitch and it runs much better. It was turning 3200 rpm's and now turns 4500 rpm's.
Im just wondering if anybody has any input?
If it was only turning 3200rpms, then the boat was under propped to begin with, 4500 is right about where you would want it to be for a stock 454 merc. How big was the boat?
I would guess you are probably running about 45mph, meaning the boat is probably... 24-26'
The boat is a 21 ft Im wondering if it should be alot faster? I should ad this was with the stock speedo...
I own an 88 211 liberator, don't know what drive he's running because they changed from merc to OMC around then, but I have an OMC king cobra and had to change gear ratios in my drive.I was running a 19 prop at 4400 rpm with a 300 HP crate motor that should spin 5000 RPM, they had some crazy ratio like 1.38 to 1 and I could not find a performance type prop in a low enough pitch to get what I should out of the boat
Dan your friends 86 is different than my 94, but I have a 21' Liberator. As far as I know they changed the hull design around 89 and look different. Mine weighs in at 3500 lbs, it is a King Cobra with 1:42 ratio & cone clutches. I run a Powertech OFX 15 1/4 X 27 four blade and at 5100 I'm at 74 MPH on GPS. I still have more throttle to go so I don't know what the top end is yet & want a little better conditions to twist it out.
I just wonder if at one time this 21 pulled 4800 and now the motor is tired out... eek!
Just a novice hear and still trying to learn but from what I remember on the 454/330 recommended operating range is 4200-4400 rpm?? I may be off a little but am pretty sure it's not 45-4800. Now the magnum motors were rated quite a bit higher.
Rich
It is the Magnum motor. I was told 4800.
I have a 1988 21' liberator with the 330hp 454 and a bravo1 outdrive (I believe 1:5 ratio). I'm turning a 21p 3 blade 15" diameter at 4600 rpm. My top end is 50 mph on gps but I hear these boats should be good for 55-60 stock so I'm working on it
Dans66Stevens:
I have a friend with a 86 Four Winns Liberator. Its a 454 Mercruiser 330 H.P. It came with a 21 pitch S.S. The boat was a slug....We went to a 15 pitch and it runs much better. It was turning 3200 rpm's and now turns 4500 rpm's.
Im just wondering if anybody has any input? Dan, There is no reason to have to prop down that far on a 21' boat. I'd get to checking out that motor and drive really well. That combo should spin a 19p at about 47-4800, and a 21 at 44-4600.
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