my options?
 

Buying a new boat is not a option, bravo BB setup is for the right price and the sale of the 5.7 setup

Starting with a Larson Senza stepped hull 25'
what can be done on a reasonable buget
I have been attaining a wot 4700 at 50mph
but have recently found out that Im using the wrong
prop for that application 21 ss vented 3 blade
I have been told a mirage, Hydromotive,or bravo I
4 blade.http://www.throttle-up.com/specials.htm
current setup is a 350mag with a 1.5 alpha gen2
driveshower thur hub boat weight 3800 dry
Im putting thur hulls corsa quick &quiet on
K&N filter/stub stack considering
a Imco powerflow setup over the stock
manifolds, as I see it a the prop switch since
I have the completly wrong type on there, slip 24%
I shoud gain 2-3 mph and 1-2 mph for the exhaust
what cost would be invold to build the motor up 70-100hp?

As far as the props go I have found that the Mirage plus is the fastest on my ddc hull. I have twins but under normal conditions the 3 blade will be faster than a 4 blade. As far as the engine goes I am working on ideas for my boat to gain about the same hp. I think the exhaust idea is a good start, if nothing else you will certainly lighten the boat. Dwight

Personnaly, I would get your 21P worked to a 20P and pick up 200 rpm. That is about the best you will do without the additional HP.

BT :cool:

Engine power
 

I wouldn't expect much of a gain at the exhaust with the small block. The stock manifolds and the through the prop exhaust isn't very restrictive. I would say that 1 or 2 MPH would be about right. You will absolutely have to change the camshaft to increase horsepower any condiserable amount. Install a cam with 212/218 intake/exhaust duration with 110 or 112 degree lobe separation angle. Call Comp Cams Hot Line.
Sincerely
Dennis Moore

Dennis, I was reading your performance tuning artical
on hotboat , I will be checking the advance on it at 3k rpm
hate to cam a 400hr motor without freshing it
besides it has the weber 600cfm carb. right now Im trying
to get her breathing a little better and get the correct prop
my slip has been calculated around 24% do to the air from
the stepped hull my vented props that I have used suffer blow out when up on plane

I agree with Whitey about the exhaust. Small blocks need headers of better exhaust too and all the thru-prop exhaust I have seen are too restrictive for any V-8 engine. Don't know about the props, though. A cam change could be a big help along with the exhaust, even with your hours on the motor. Exhaust and a Whipple would be nice..............
Good luck anyway and if I can help, pm. :eureka: :D

24% slip, that is terrible. I would also ck the x deminsion and be sure it is not to high. If that seems normal I would probably look at a 4 blade prop. The 3 blade will be faster but only if you can hook it up. Dwight

To gain 70 - 100 hp per engine, or total? Per engine will be tough without alot of work...Starting with a stock 5.7L (260 hp), I stroked the motor, rollerized the lifters and the rockers, added Corsa Captain's Call selectable exhaust, replaced the heads with World Products SR Torquers, and am running a Crane .508/.528" cam w/ 1.6 ratio rockers. Dyno tuned at 380 HP with the Rochester Q-jet. If you are only trying to get 35-50 per engine, you can get there through a cam, rocker and exhaust change. Without the exhaust, you'll be taking a chance that the extra breathing will get choked down. Alpha drive runs all exhaust thru about a 1-3/4 to 2" hole in the outdrive if my memory serves me.

Normally aspirated, if you pay attention (and don't go ballistic with the $) general rule of thumb from the Dyno shop: 1 hp/ ci and you're doing pretty well...beyond that, bang for buck goes down fast.

whipple or procharger blower and through the hull exhaust.

406 long rod Rag's

EASIEST Horsepower is going to the Vortec heads ($400-500 COMPLETE). with a edelbrock performer and these stock heads you got 50 hp right there not to mention you have NEW heads! Your motor could probally use a valve job anyways this will just save you the hassle .......Take your camshaft and retard it 4 degrees and add some new 1.6 rockers and you will get your 70 horsepower (or damn close!) for probally about $700.00. Here is where I got mine. They have some good info about them too.
http://sallee-chevrolet.com/Cylinder_Heads/Vortec.html

Bad-Habit