cobra marty

Tell me more about this drive beyond the basics.

What is the distance between the input and prop shaft?
How much shorter does that make it vs. the bravo?
Recommended mounting 2 1/2" above std. bravo 1.
What props available? Pitch? Will bravo 3 props work?
What ratios are available? Will B1 upper gears work in it?
Where do they break?
What upgrades are available?
Are internals all B3? and only the case and vertical shaft different?

Thanks.

Cattitude

CM- John's been experimenting on his 25 Daytona- he can tell you all you want to know I'm sure. Dollar used to have some new ones too. Good luck!

Ken

Vinny P

Marty,

I recently sold a motor I had to Alamo502. He used to advertise on OSO motors for sale a while ago. He had a Black Hawk drive sitting there that was dissassembled. I didn't really look close at it, I don't know if he has all the parts for it. I just figured I would let you know this. If interested ask for Kevin 732-751-1200

blackhawk

The blackhawk basically has bravo 1 upper gears and bravo 3 lower gears/propshafts, etc with a shorter vertical shaft in a one piece case. I am not sure how much shorter it is than a Bravo 1. Bravo 3 props would fit on the propshafts but would not work since the blackhawk is a surface piercing drive. Mercury made 27", 29" and 31" pitch props that were 15 1/2" in diameter. Most popular ratio was the 1.5. But they also made 1.36, 1.65 and 1.81. I believe the upper gears are their weakpoint. That and you have to keep an eye on the props for stress cracks near the hub. A blackhawk drive will not work on all hulls. Most cats respond very well to them but a deep V needs rocker in the hull to get good bow lift. That's about all I know

tomcat

The Blackhawk drive is about eight inches shorter and can be mounted almost 2 3/4 inches above a standard Bravo. The two props maintain the bite at this height, but it takes a good engine to turn all that blade area at idle. That's supposedly why the drive was only sold with the 502 MPI engine which supposedly had an extra hump in the torque curve just above idle due to the plenum design.

In 1993 Archer Marine Special, a 26 foot Scarab, bumped the "A" class record from 84 to 93 mph using the Blackhawk drive. That was a big deal back then. The fact that the same boat rolled after hitting a wake during an attempt to break 100 mph seemed to cast a shadow over the drive. I think Mercury was too quick to dump it. People said it was too hard for boat builders to design for that drive but look at the great lengths we have gone in recent years to raise propshafts. Now we're so high that we need five blades to keep enough blade in the water.

Guess what's after five? Six!! And that's how many blades the Blackhawk drive had. I wish they would bring it back.

blackhawk

Tomcat, I agree. I think that if some boat builers would have put enough time into hull design that the blackhawk would still be here. You cannot just throw this drive on and hope it will work. My Donzi Classic has a re-worked hull for the drive but I feel there is still room for improvement. It's my understanding that some of the cats responded extremely well to the blackhawk.

And the idle thing is interesting. I had heard that the Blackhawk equipped boats had a lower idle but never heard of the torque bump. I know when you put her in gear you're moving. My boat idles at 500 rpm and just over 6mph. Makes for some interesting docking!

Cord

iTrader: (2)

My understanding of the reason for the 502efi, was that it was the motor that was capable of a 500rpm idle. The low idle speed was needed to keep boats below the 5mph no wake speed.

blackhawk

Too bad it didn't work! My boat idles right at 500 rpm and that is usually 6.1 - 6.3 mph on my gps. If I trim up it's slower but then it actually throws more of a wake because of the angle. I don't know how many times I have been *****ed at for going too fast through no wake zones!

tomcat

I seem to remember another article where they replaced the Bravo drive with a Blackhawk drive. Picked up a few mph but mentioned that the (supercharged?) engine stalled when put into gear. This problem and the idle speed could have been addressed another way; just engage one prop at idle (two stage clutch?) Sounds like a job for Weismann.

shifter

If you call Dan at Archer marine he could tell you all about the failures of that piece. I know he still has some pieces there.
I found the same problem with the volvo single vs dual, motor stalling high idle speed ect.. One solution .... downshift.
pat W