your 900RPM short of your peak HP. What does the dyno sheet say for 4900RPM's? What are your TQ #'s. If the motor is built to spin 5800 the you need to spin it. Just watch that outdrive if it's a Bravo 1 it's not going to like spinning close to 6K RPM

I was thinking rev limiter too.
Have you checked the timing?
What's the correction factor on the dyno sheet?

I have a 23 Nova with similar engine/dyno specs. The Nova ran +70 gps with a ZZ502 and a labbed 25P. Now runs low 80s gps with a stock 27P and bravo 1 at about +,-5500 RPM. Engine's not even breaking a sweat but do worry about the B1 LOL

Who dynoed your motor? 700 hp is obtainable N/A from a 540 BUT motor would have to have ALOT of cam and outstanding cylinder heads, nothing run of the mill. What Cylinder heads do you have? I have a friend who also built a N/A 540 that made over 700 hp (at 6800 rpm's) but the cam was a giant solid roller and sucked for marine use, I borrowed him several props,he previously ran a 26 labbed, boat would not rpm even close to the cams peak until he went waay back in prop pitch and then oil ran hot, boat had no cruise speed, sucked all the way around. There is a supposed engine builder in PA that has inflated dyno sheets and outrageous correction factors, I hope you aren't another victim of his, Smitty

You haven't taken it above 4900rpm or that's all it will spin up to? That's way too low. I have N/A 540's and true 700hp. Max rpm's is 6500 on a hydraulic roller set up custom cam and worked aluminum heads so 700 is easily doable. Your definitely not spinning them fast enough for some reason? Gear ratio in the drives won't make that much difference in rpm so long as the right props are used. my guess is spin them faster to 6000 and see where that gets you. If you can't them you have other issues, rev limiter, lack of fuel, wrong props too tall, timing not advancing, etc?

Sounds like its starving for fuel. I have a 540 700 hp in a 29 fountain and it hulls ass.. find george goble on here, he has a 1996 26 scarrab that runs over 100 mph. goble 1

then @ 4900 you may be only at 600hp or less....what ignition are you runnung ?

I'm pretty sure the builder is not playing with the dyno numbers he is a family friend and has built motors for our race cars inculding a 1200+hp procharged small block ford!! But yes i def do have a prob! I'm running worked AFR cylinder heads msd ignition and distributor with a 6000 chip the motor made its peak power at just over 5562rpm. I found my dyno sheets and i was off a little on the numbers it made 689.4hp @5562 and 650ft/lbs @5562. The cam is a solid roller set up. Also a Quick fuel 1050 carb. Thanks for all your help guys!! I just hope i can get this boat to run faster soon!!

Did you change your pickup tube in he fuel tank 3/8 wont get it. I went to a 5/8 tube. You can have pressure but not enough volume. Are you running a bypass on your aro 1000. Also check your vent from your tank to the outside of the boat I had to take the cap off and cut the vent back to open it up. Take the dang mercury computer out and throw it far way.

Couple of questions.

Was that dyno run with all accessories through the same exhaust you have on the boat now or was it a bare block hooked to the dyno using the dynos waterpump & with dry auto exhaust with huge pipes and collectors?

This can make a huge difference in output to the prop.

What the fastest similar sized scarab running with similar power-? Scarabs are heavy and arent known to be water rockets.

a 700 in a 26 should rock balls. Something isnt right you're either starving for fuel or the prop is buried way too deep.

It should rock - my heavy 28 has 700hp and it runs 90 with a light load and 1/4 tank (25 gallons) on a mid 70 degree day and mid to high 80' all the time spinning a 4 blade 28.

Uncle Dave

Yhe key is why is it only turning 4900?