speed

[wsm9808]

Damm, All this talk has got me wondering if I put the wrong impeller in for my set up.
Boat is a 19 ft tunnel hull with a fresh Dominator pump and american turbine A impeller with a place divertor, droop, shoe, ride plate and small loader with the two peices of angle welded to the sides. I overhauled the pump before I started coming to this board, so I was just guessing at the pump set up.
Engine is 468 bbc, with 9.6 compression, closed chamber O-port heads with 2.19/1.88 valves and full bowl port and match. Cam is .544 lift and .230 dur @ .050 on 109 centers. Tall single plane intake with 780 carb exiting through logs and Rex inline mufflers converted into through hull tips.
Boat runs 70mph on gps, 75 on speedo and turns 5200.
Would a B impeller add a few more mph?
Would a different loader help?
And, for you guys with NOS, how much increase in rpm/mph do you get with a 100 and/or 150 shot? I'm wondering if a 150 shot would et me to 80mph.
Pics of the boat are at.. http://www.liquidaddiction.net/Karaco.htm
Thanks, Scott
[This message has been edited by wsm9808 (edited February 02, 2002).]

[77charger]

that is the same nitrous kit im putting on my boat from people who have tried yhe 150 hp have picked up between 450-600 rpm.As for the impeller a b cut would probably pick up speed but will increase your rpm by about 350-500 rpm.It helps get your motor to the peak hp range.If your motors hp peaks at 52-5300 then a b would do you no good.I would call a pump guy to have him explain it better.I have talked to jack at mpd(949)631-2040 about his and had him cut mine down too.Went from an a to an A-B and picked up450rpm but then again my motor peaks at 55-5600 so my new one is cut to a b+.Remember once you cut down its permanent meaning you can only cut smaller and cant go back to an a cut unless you buy a new impeller.I was talked into trying an A-b cut first to see if it helps before going to far and im glad i did as i think the b+ cut will work great.

[HBjet]

wsm9808, I think either a AB or B impeller would put you closer to the 80mph mark. One thing I see holding you back are the exhaust logs. Ever though of either over the transom headers, or even the Bassett thru transom water injected headers? That will give you more HP then what your running now. Good Luck.
HBjet

[Bense468]

I would not go with anything less then an ab if you are shooting for more top end. The reason why is because you are going to start pushing the boat up towards 6 grand. If you are set up with really good components then this should not be a problem every once in a while. Its just my opinion that once you start taching them over 6 you are going to start having issues of reliablily on hand. If that is not an issue then do what everyone else in here does to squeeze out the big top end numbers. Just cut the impeller. If I was you I would stay with the a and maybe think about a few other options but that is me. I like the boat to be quick. You start taking away the "pull" the hard launch of the boat the smaller the impeller.

[Bense468]

Like Hbjet said just the logs alone are holding you back. If you are at 75 I would bet you would be closer to 80 without the logs maybe 1 or 2 mph shy.

[wsm9808]

I've got a set of Bassett OTs that were on the boat when I bought it, but the lake I use the most requires through hull exhaust. I already had the logs so I used them rather than drop a couple of grand into some new high flow pipes. I concidered the through hull bassetts, but I want something on the boat that wont burn you if you bump against them.

[Unchained]

WSM9808, I have a bronze B impeller for a Dominator and the wear ring. I also have a closed center loader that I have been using, Greg suggested I go back to my old open center. Come to think of it I got a spare droop with fine tune nozzle laying around too. If you want to give them a try that's Ok. I'll hold those old pictures of your boat for colatteral.

[froggystyle]

What is a JPC? How do I do it? When it comes to stewed prunes, is three enough? Is four too many?

[wsm9808]

Thanks Unchained, I would like to try another loader to see if it helps, but I want to install an intake pressure gauge first for a before and after comparision, and it will be a couple of months before I take the boat out again, so if the offer is still good later I'll email you about it when I'm ready to play with the boat again. As for the impeller, I dont think I'm going to change it unless someone can convince me it would make a significant speed increase. That blasted transom adaptor on my boat is a pain in the a$$ to get on and off with all that silicone mess on it, I would add NOS or a Blower before I would pull that adaptor again. That is a very generous offer however. Thanks
What are ya'll using for a intake pressure gauge? Would an oil pressure gauge work?

[Unchained]

For a water pressure gauge I am just using a basic hardware store cheapy. The needle wants to bounce a lot at high speed. It would be nice to have a liquid filled unit or I even thought about an electric oil pressure gauge. I need to relocate my pickup point. I have been using the factory hole in the dominator pump. Greg suggested I tap in on either side of the hand hole cover at 10 or 2 o clock so I am going to try that in the spring.