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kevinb
05-20-2002, 04:19 PM
I have a 26ft Firehawk cat that weighs about 4,000lbs dry. I figure with 50gal of gas and all my gear it weighs in at about 4600 lbs, plus people.
For power I have a 454with:
comp cams (see cam card here: http://www.netprofithosting.com/camcard.jpg)
It has an edelbrock short intake
holley 850 double pumper carb
and nice Stainless Exhaust Manifolds
I have a Bravo1 24" pitch prop
My boat will drive up to only about 4300 rpms, which translates to 60mph. It moves up to 4,000 rpm quickly, then crawls to 4300, 4500 if I trim it up high.
what horsepower should I expect from this motor? Shouldn't this motor push the boat to 5500 rpm and above? I know a 496 in a new firehawk comes with a 28" prop. Am I really that low on power?
Is the right cam in the boat? Am I set on "reliable" or "hi perf" with this cam? At what rpm does this cam peak? What would you say redline is on my motor?
With the short intake, am I robbing myself of top end?
What about the prop? Is 4 blade best? why is that? Any other prop you suggest?
I just tried out an MSD ignition and there was no change. If I put the boat in neutral, it will rev up to 6000 rpm, maybe higher... so I know it's not the rev limiter.
The fact is I'm no faster than a 29 profile Vbottom with a 454 mag and I'm actually slower out of the hole.
What is most important to me is cruising speed, so putting on a smaller prop is not the answer I'm looking for. I want to make my boat pull to 6,000 rpm so I can put a bigger prop on it! I think this motor should be able to do it... so now I'm just trying to figure out why it's not. Any info/data you can give would be appreciated!
Thanks
Also - does anyone know what a 25' eliminator daytona with a 454 would come with as a prop? If it comes with a 21 or 22' prop, maybe I'm expecting too much. But if it comes with a 25 or 26 like I bet it does, I'm bummin.

pleasantcat
05-20-2002, 04:54 PM
well, its like this.... i have a 25'daytona.big block chev power bravo1 with imco lower. i spin a labd 28" bravo prop. i know from dyno pulls that i make well over 600 ponies. high 80's to low 90's is all i can get out of this boat. i'm now to the point of, if i wanna go fast i need more ponies. i think you may be in the same boat....

Bad Puddy Tat
05-20-2002, 05:31 PM
My previous 2 boats I had slightly modified 454's in them. Typically they were producing somewhere around 400HP. Like yours they would pull hard to around 4000 RPM and typically dependant on conditions they would max out between 4500-4600RPM for speeds in the low to mid 60's.
I'm now driving an HTM SS-24 Originally I had a 565 Cu. pulling dyno verified 679 HP. My boat is aproximately the same weight as yours this motor would pull to 6000 RPM and push the boat at 92 MPH on GPS.The prop was a bravo one lab finished 26 pitch.
Now I have put in a 572 with a stage 3 procharger 1000CFM carb (modified) Changed the outdrive to XR with 1.26 Gears. This setup makes 875HP I haven's opened it up all the way yet GPS reads 112 MPH at 5600 RPM The blower is setup for only 5LBs of Boost. I was after the acceleration not TOP End. But since my place is in Parker The opportunity to open it up for any distance is few and far between.
It seems that your numbers are about right it appears you might have excessive prop slip. Hope this helps and safe boating

boatnam2
05-21-2002, 06:46 AM
kevinb,i had an american offshore which is the same boat you got it came with a 454mag 385 horse i think.it ran mid 60's .your not going to see anything near 6000rpm unless you put some big power to it.to spin an i/o 6000rpm is tuff to do.i cant remember what prop i started with when the motor was stock but that boat is always going to ba a slug out of the hole its the nature of the beast.

Duck
05-22-2002, 08:30 PM
kb, I once had a 300hp 454 in my 25 Daytona with a 22 prop and went 54 at 4600. Met a guy with a HTM same combo, same mph.
Build a motor, you'll never regret it.
Duck

FastCats
05-24-2002, 06:08 AM
Make sure that the engine is making all of it's potential power first. Put a timing light on it and rev it to 4000, does the mark move around or bounce? If so you have spark loss which will cause top end power loss which is where all of your cyl. pressure is. Check plugs, wires, cap and coil. From there put on a smaller prop to see if the boat will run to higher rpm under load.
Scott