What is needed to go faster?

[mud duck]

Last Saturday I finally wound up my new motor and got 56 mph on gps (60 on the speedo). That was with five guys, a full cooler and lots of gas on board (and one ski) in a 21' Ultra open bow. Now it is a 540 motor with a B&M 250 blower producing about 650 hp. I have the Dominator S-12 pump, Aggressor bowel, droop snoot, Place Diverter, loader grate, stock ride plate. I believe it is an "A" Aggressor alloy impeller. What more can I do to get a bit more out of her?

[MikeF]

What rpm are you turning now? (@56mph)

[mud duck]

About 5,500 rpm @ 56 mph. My rev limiter is set at 5,600.

[572Daytona]

You didn't do any speed runs without all of the passengers? It is going to be really hard to acheive better speeds with passengers sitting in the bow area since you will be riding way too wet. I'm seeing 90mph with similar HP in a 21' but I have a tunnel hull that can take advantage of lift. I would think you should be into the 70's at least without your passengers.

[dtr352]

Take the people out of the boat and see what she does. My buddy has the same boat with only 500 or so hp. With two or three people he runs 70. To get a good idea of where you are at get rid of some of the people. How old is the pump. You could be sacrificing power there. Just an idea

[mud duck]

Yea, we had a whole lot of wieght on board. Two of the guys were sitting in the front open bow (not the lightest two guys either). The hull is approximately 2,700 lbs, I believe. Which does not help matters, but it provides a great ride in the chop.

[MikeF]

Looks like the impeller IS doing it's job and holding the rpm's at a reasonable #. Todd's Rogers has a 540 (unblown) w/ about the same power but w/ an A.T. "A" and his max rpm (so far that I have seen) is right @ 5.5k too.
Your's is a heavy boat and you may not get much more out of it? It pretty much sucks when you throw alot of $ at something and it does not work quite as well as you would have liked it to.
I'm sure others will chime in. Maybe there is a little more? Might try a slightly higher rev chip to see if that is what is holding it back. :clover:

[mud duck]

It is a 1998 boat & pump, new motor. I did get 72 mph (on the speedo) out of her with an stock 454 gen V motor and the same B&M 250 blower on top. Of course I melted that motor last fall. Perhaps 72 mph was a bit more than that motor could handle. I think my speedo is just about four mph off on the high side, so it would really be 68 mph. The 56 mph last Saturday was on gps.

[MikeF]

Do you remember the rpm @ 72mph w/ the old engine? Was the pump the same then too?

[Squirtcha?]

Take the people out of the boat and see what she does.
With my boat, one 180 lb passenger scrubs off 5-6 mph (measured with gps). That's with that extra person sitting in the front passenger seat (not over the bow, or forward of the hull's mid point). I've found that you really need to be consistent when chasing after speed. Since I'm mainly concerned with how fast mine goes while racing someone, and 95% of the time I'll be by myself when racing, that's how I'll test when making setup changes.

[Squirtin Thunder]

Dan,
Your boat made Hot Boat in the Freeboard Chalenged secion.
Jim