prop testing need help
 

I have a 2000 32 active thunder with 500 hps with a refresh to about 560 per side, my original prop is a 30 b1 labbed heavly, verry thin, i am now getting into the rev limiter at 5500 it runs 86 on gps up 3 mph from last year,so i tried a stock 30b1 only spun it 5300 at 83 mph but made the boat porpoise bad on top end, then i tried stock 32 b1s with a cupp in them im told to about a 33 only spun them 4700 at 83 mph but again porpoise bad on top end but did pick up 5 mph at 4000 rpm, my original props do not make the boat porpoise at all. im lost what to try next.

The standard 30" B1 prop, unless the pitch has been changed is about 29.25". Based on your WOT numbers with the 32 worked to 33 is way too big.

I was at your point with my project. Right now you are at 16% slip at 5500.

You have three options:

1. Change to adjustable rev limiter ignition and run the 30's.
Easier on the drives and a little harder on the driver train.

2. Go to labbed 32's. Maybe a little more speed. Probably the most expensive option of the 3 if you buy new props. Used could get even with the other two options.

3. Look at nose cones. I ran 90 mph last weekend with labbed 30" bravo i's at 5450 rpm with cones, 2 people 3/4 gas, 10% slip. Probably not much hp more that you after 3.5 summers on the motors. Nose cones cost me ~$600 doing the work myself. Nose cones will lower your WOT rpm by reducing the pressure wave in front of the bullet so that the prop gets a better bite. So you shouldn't need 1 or 2.

Come to LA and I will let you try my drives and we can drink some beer and talk boats. :drink:

BTW LA is Louisiana not Los Angeles. The Royal Purple Poker run is June 20th come on down.

DO NOT USE nose cones!

so prior to the engine work the boat was only going 83 and not pulling the current props to the rev limiter?

yes correct

so the boat is 5mph off at the same rpm.? if the engines were loosing power then your rpm would be coming down with speed. if your speed dropped then u have problems elsewhere.

and you will know when you are on the rev limiter...it cuts out big time! those tach go over 5500 maybe 5600 and still be off the rev limiter!

ther at 5500 to 5600 then you can here it it is in the limiter , i back off to 5400 or so and all is well, thinking i need a labbed 30 that is not labbed so thin like the 30 i have now but i concerned with why it porpoises with the other props and not the ones on the boat.

not really 5mph off as it only ever went 86 the 1st year i had it and then slowly down to 83 or so, must have been faster where you ran it as i run on a river with no chop to help out. ive only lost 3 mph obver 4 years and i added a 4" wind screen acroos the front that may of slowed it down a tad.

the props u have are not even all that thin.

u need to first send them to throttle up propellors have them scanned. this will give me numbers i can use. anything else is guess work as the props may have changed! with my input we can get you back on track. and more if your budget allows?

second u need to look very close at the bottom of the boat.

that boat had the ability to hit 90mph no problem with the setup that was in the boat minus props.

second u need to look very close at the bottom of the boat.

that boat had the ability to hit 90mph no problem with the setup that was in the boat minus props.[/QUOTE]


Glad you jumped in. What is the deal with the bottom, who, how what do you look at? That is my next step.

If Rick's boat went 90 at one time with stock power, can the hull get a hook or whatever over the years sitting on the trailer???

Understand nose cones are controversial but they helped my boat.

Tom

fresh water will be slower than salt.

yes the boat can deform on a trailer! and the longer it sits the worse off.
as an example if you toss a 2x4 under one of the wheels on a trailer it will twist the hull(even a race boat). always have to boat on level ground and there min pressure should be on the tongue jack.

it can all be fixed.

nose cones increase surface area...PERIOD...your boat is not fast enough to use one. another prop would have been faster for sure.

rick, i will work with matt and julie at throttle-up props to hit ya a home run. if your making over 550 each then 90 should be cake!!!!

first we need to get that bottom worked out! something is not right and a wind deflector is not going to scrub that kind of speed even if you were going 100mph.

not on every boat!
the only sure thing is it's different.

all my big numbers have been in fresh!

unless ya wana count going through the dog leg in biloxi at 193. lol

ps...the props ya sold off were very cool...they were designed to run at 71mph at 4000rpms with fuel milage at about double over the ones u r running now. the ones u r running now r worthless unless u r running the boat over 5k! u may want to buy those back if ya can.

none the less we can make ya another set.

so should i straight edge the bottom looking for a hook, and could that be the porpoise problem with the other props i tried ,,, strange though it does not do it with the props i have been running. Would like to see 90 plus with the power increase, i have a poker run to do next weekend so dont have much time to play with props till after that. Thanks Rick

the props you are running i built. and i would never build a prop to carry the bow more and have the boat less stable for 1mph. which can be got somewhere else anyway.

i'll help ya but the first thing is they need to be sent to throttle up props asap to be scanned. this part can be done this week.

I have a 2002 stock hp500 found the best speeds out of 32b cut down tried stock 30s did not run as well. The best results were after I blue printed the bottom, had a bad hook, picked up 2 mph with the bottom and adjusting the drives. Ran a solid 85 2 people half tanks.