wfo1

I have a question for you Velocity experts. How does a full cabin side by side 390 handle over 100mph? I know there have been some fast staggered 390's, and that one at ducky's I would assume is well into the 100's with the 850's. What kinda speeds can I expect with 700-750 a side? Just trying to decide how much motor I want to build this winter.

sl

iTrader: (2)

Mine is a side by side with whippled 525's that dyno'd at 790hp. I run anywhere between 98 and 101 depending on load and conditions. Maybe 1 or 2 mph in it if I played with props.

wfo1

I would have expected more with 790hp. I had mine up to 83 gps with tired 575's and 200 gallons of fuel in it before I ran out of lake. That's with props turning out too, which from what I have read isn't best on velocitys for speed. I'm hoping to get an honest 100mph everyday.

Revelocity

The above speed is right in line with my friend's former 390 (Tsunami2) that initially had ~800 HP side by side and was around 99 MPH using Konrad drives and a high x-dimension. You'll need the NXT drive set-up and Speedmaster props to get to the hull's full potential! I've heard that the hull maintains its composure at 100 MPH but I don't know first hand.

wfo1

The red/blue on white boat with 565s ran right at 100mph supposedly, and the blue one with 700sci's ran over 115 right? Both staggered, and one with nxt drives. Maybe I need to stagger this thing before I drop motors back in.

Revelocity

Actually the side by sides are faster according to Steve Stepp as the staggered boats have more hull drag. I forgot about the 565 boat - it must have been dialed in perfectly with a real light layup!

wfo1

Yeah, I was told the same that the staggered boats are slower. The speeds from those 2 boats don't really sound like it though. I could see the 700 boat being a different animal due the NXT drives and props, but that is a hell of a difference. I guess I will shoot for low 700's and turn up the boost if I don't hit my goals.
Thanks for the input!

ziemer

iTrader: (1)

What should it run and exactly how to get there? My experience is not with the 390, so specifically how to get there I can't say. However, what I can say is that the smallest changes can make exponential results.

It's not just about dropping a set of big horsepower motors in and running over a hundred.

Props, x dimension, drive toe, driver skill, bottom shape, condition of the running surface (especially the pad) can all make drastic improvements for speed increases. Every little bit become increasingly important the higher the speed.

My 30 with the same motors ran 70-72 when I first test drove it. With drive toe adjustment and indicators adjustments alone, the boat gained 4 mph. With a prop change, another 2. Now with fresh top ends and new exhaust I'm up over 80 and some prop tweaks are coming for which I believe a few more a there.

My Allison was similar. First time out with a newly installed 260, I saw 93-94. After several changes and a fresh rebuild (though still a stock 260), the boat will now run well over a hundred with a best of 107.

Both cases, HP remained essentially unchanged.

One change and a time, along with practice and plenty of patience will get you there. A person with specific experience with that hull can speed the process up too. However, it's amazing how much the same model boat can produce different results.

sl

iTrader: (2)

Didn't mention in previous post I switched from xr's to IMCO scx's. Lost 3-4 mph with the change. Even with the original xr's, it would take a lot of dialing in to try to get in the range of the blue staggered 700's speed.

wfo1

Sl,
Are you running bravo style props or speed master props on,your scx's? I figure at some point I'll end up going scx myself. I really don't see these max machine worx drives holding up long term.