Lot of thoughts traveling through my head lately....
Winter is coming and dreams of more horsepower are weighing heavily right now.
Would like some "real world" thoughts as to how much horsepower will be needed to push my boat to 80 mph (GPS). Right now I`m hitting 66 @ 4600 rpm with 310 hp spinning a 23" Mirage Plus. Here`s the details of my little boat:
Baja Hammer. 21' 4" length. 4000 lbs "running weight".
1.50 ratio, Bravo One.
20 degree deadrise
I would like to keep max rpm`s to about 5100.

Thanks for your input!

A friend of mine did slightly over 80 mph, in his 21 Checkmate with a 540ci. 580hp motor.

Your speed number gives only 2% slip, not likely. I jimmied the numbers a bit and get the following results for a 454 Mag and a 575SC.

There is no free lunch!! It is highly doubtfull that a base 454-310 could economically be made to make 600hp. No forged goodies inside....... just get a 502/502 and add a 3-5# Procharger....no muss no fuss..... if the boat can handle it youwould see over 75/80 on GPS.... My old 454-450 + Procharger at 5500# dead weight & 25 ft went over 75 on GPS so yours should break 80....
If you could walk afterwards!! (pucker factor no in the above equation!!)

1988 Fourwinns Liberator 21' running weight about 4200lbs. OMC King Cobra 1.43 gears 5200 rpm 25" Ballistic Prop. 540 cid Ford dynoed 625ph 710 ftlb torque. This combo would bury 80mph speedo. Didn't have GPS when I owned this boat. My guess is you'll need bare minimum of 500hp , probably closer to 600 would be a better bet.

This will make your 4000lbs+ baja go 80 MPH

80+ Baja

Looks like TC has hit it on the head, At one time I had something close to 500hp at the crank and saw a 10mph increase on the same boat. Mid 5s to 6 should do it, and the drive might have a chance of living if you take it easy.

I had a 23 Baja Bandit with a reworked 502 Mag that made every bit of 600hp that ran 80.

Looks like I should shoot for 600hp and maybe I`ll have a little to spare. No, I wouldn`t try to make this 310hp engine put out 600hp. I`m thinking 496ci or possibly 540ci. Lots of $$$ for a 540ci though.

think about external steering as your first upgrade....always work from prop (bottom) back to the engine....the very last thing i would do is the engine...in any boat for that matter...