Tinkerer

OK - so last year I had an 1.5 ratio IMCO -2 shorty and a 28 BRAVO 4 blade and the boat got on plane with only a little slippage.
This spring I installed a 1.36 ratio -3 shorty and the boat wouldn't even try to get on plane. It would blow out almost instantly.
I borrowed a stock Maximus 26 pitch 5 blade. Now the boat gets on plane with the engine at 4000 rpm for about 14 seconds and a lot of slippage. AND the boat handled terrible.
No speed and the bow was stuck to the water, And NO roost.
After talking to Bret at Bblades for about 30 minutes and tossing ideas back and forth I came up with the idea of tucking the drive under the boat farther.

I was able to cut a little here and grind a little there and shortened the trim ram inner rods 3/4 inch.
Tonight Was the first chance to water test it.
AND it worked.
It hopped right up on plane with the 28 Bravo. It is a small lake and I didn't want to get in trouble so I wasn't able to test it at speed. BUT I did nail it twice for a short stretch and it felt MUCH better.

Next step will be to take it to Hardy Pond and try it out.
Bret wants to know how it handles and what speeds at what rpm's.
He thinks that if I could get it on plane a BRAVO 30 pitch labbed Would be what I needed.

I am so happy. I have had a bad two weeks and something went my way.
I spent $8900 in the last two weeks. ( $6000 on a new trailer, $350 on temporary trailer repairs, AND $2500 repairs to my work van )
__________________

pstorti

iTrader: (2)

seems like the root of your problems is the -3 shorty why not go back to the -2??

Tinkerer

It was too deep. At speed with a cat you trim it back down for better efficiency and top speed. If I trimmed it back down I would lose RPM and speed. After talking to Bob Leach I decided on the -3 shorty. Bob told me the ideal prop shaft height is 1 inch above the lowest point on the bottom of the hull. I now am at 7/8 inch above.

glassdave

iTrader: (1)

a friend of mine is working on his 26 Daytona at my shop right now, those things came from the factory waaay deep. His solution is going to be one of these . . . . its like a -7 shorty


he filled the transom and has not decided on an x dim yet, guess he's gotta do some math yet.

Tinkerer

Dave - I did a LOT of research into Blackhawk drives - even had one lined up to buy. Bottom line they are great for top end but suck for everything else. Props are hard to find and expensive. lots of vibration. And they won't handle more than 800 HP for long. ( I am building a 900 HP 598 )
The trick with the Blackhawk drives is the water coming off the back of the hull has to just hit the bottom of the bullet. And I think they are like 9 inches shorter. Tom Earhardt experimented with Blackhawk drives. He even cut one in half and welded the lower to a Bmax upper.
He still has it I believe. I may have to ask if I can try it once.

punkinhead

Sexy sexy, those Black hawks scream fast!

onesickpantera

iTrader: (1)

Damn! Modified blackhawks? What was done(besides the obvious propshaft swap)?

glassdave

iTrader: (1)

these are single propshaft Blackhawks. I think Max's makes them, be interesting to see how it works. I think I have a pic of the Bmax/BH drive somewhere.

What is the x dim on your Daytona?

JRider

iTrader: (1)

Correct me if i am wrong but the -3" does not have the cave plate extension, my boat with a -2 and no cav plate extension would blow out and never plane. Cav plate extension installed and 5 blade prop problem solved.

Tinkerer

-3 IMCO does come with a cav plate extension.
My prop shaft is NOW 7/8 inch above the lowest part of the hull. ( about 10 inches forward of the transom )