tnt1

91 42 lightning staggerd #4s on boxes one intch below bottom 900 hp blower motors herring 18-31 18 deg rake can only get 4500 rpm 80 mph also tried some merc 18 -26 5 blade 84 mph @ 5100rpm all trimed out are these hulla that slow ????

Meshikinquah

iTrader: (1)

Something is wrong, either your drives are too low for the props that you are running or the props are too big for the power that you are making. You are not getting into your rpm range. I would guess that you should be well into the 90’s if you making 900 hp. Someone should pop up that is running #4 drives to help.

Maybe the guys at bblades can help with a prop size : http://bblades.com/

MILD THUNDER

iTrader: (3)

Hey Tommy, Dan is having similar issues with his Flatdeck cig. 17.5x28 5 blades just are too much, even with his 1.58 ratio drives. Cant even get to 5000 with them. I'd like to try those 26's you speak of on it?

Anyhow, about yours. I know its a different animal, being staggard, and a 42, but my 4's are 1.5'' below the bottom. 5 blades slowed me down big time when I tried them, and they were only 16.5 diameter. I know everyone gets excited about 18'' diameter 5 and 6 blades, but, I think you may wanna see what some heavily cupped 4 blades will do on it. I don't think your high enough to truly warrant a 18'' diameter 5 blade wheel. I know ive tried 4 different sets of 4 blades on mine, all similar diameter, and similar pitch. Some wouldn't even plane, some planed like it had TRS mounted 5'' below the bottom. Weird.

Last summer on my non stepped 38 with IV"s, I saw 88 on gps, turning 17x28 4 blades at 5600ish. Engines made around 760HP at that rpm. At 6000RPM they make 800hp.

I have a mint set of 26 spline 17x29p 4 blades. They aren't heavily cupped and don't plane as well as the small shaft 17x28's I am running, but might get you an idea of which route to go once on plane. Dan tried them and had a hard time planning but it did get up. He didn't go WOT, which was what the whole purpose of trying them. We may try those again on his this weekend to see whats up, and where to go. I think those 5 blades he has now are just too much for that setup, esp since he put 2'' spacers in. Its all trial and error. You'll see 90 or better, just think its gonna take some tuning. Cant wait to see the boat. What ratio are your iv's? We thought dan's were 1.5's, but after tearing them down and counting teeth they are 1.58.

TRL505

To much prop....try 4 blades as MT stated.

tnt1

joe thanks for your input the drive ratio is 1.50 let me know how dan turns the 29s

MILD THUNDER

iTrader: (3)

Will do. We're gonna give them a whirl and see what happens. Maybe tomorrow depending on my work schedule.

MILD THUNDER

iTrader: (3)

Tommy, I have some vintage magazine articles in front of me.

First boat, was a 1985 12 Meter side by side. With 700HP Turbo engines, and ssm 3 drives, radar was 84mph. Turning 17x28 props at 5500. (prob 3 blades in 1985)

Next boat, 1994 42 Fountain non stepped Staggered 800SC with #6 1.50 wet sump drives. The 800sc's were actually rated at 700HP. Boat ran 84mph on radar, turning 17.5x30P 4 blade cleavers to 5200rpm.

Maybe in the next few weeks, I'll bring mine up to racine, and have dan bring his cig up. Maybe get you and kris out. It can be a weekend of old cigs and old fountains, maybe do some testing and tuning.

tnt1

joe interesting #s the 42s are a little sluggish sounds like a plan on the testing let me know

Back4More

I also agree with the 4 blades

ICDEDPPL

iTrader: (1)

I`m hoping the boat wakes up with a set of different props, right now its like I`m towing another boat, from 3500rpm I give it full throttle and its a turd, not much happens.