Cord

iTrader: (2)

Ot-I know that you have a pair on the back of your boat, but let's look at the pic that I posted above. I'm going to simplify this for the other members that are not as familiar with the drive as we are. Do you see those slots in front of the props? That's were merc piped the through hub exhaust. This was done to ventilate the props loose when planing and shifting. I assumed that they were using silent choice to do this due to the restrictions of the standard wishbone and transom. On my boat, I don't have silent choice. Instead, I connected a hose to the block off plate and ran that to a point above the water line. Gary also suggested just removing the exhaust bellows. Wish I had thought of that because it would have been much simpler.

As for the speed records, I'm certain that several people were using them for this purpose. I know that Archer made a good run for the kilo record. I believe that they rolled the boat (P-29?) and never got it though. I also believe this would have been done on the west coast, but that's only a guess.

Those props were on a Donzi Blackhawk. I presume that this is one of the boats that you were refering to as the drive working well on. I guess that credit should be give to Donzi for redesigning the hull for the drive, but we both would have to admit that results seem to be mixed. It almost seems as if Donzi put too much rocker into the hull and ended up with some freeky handling issues. Anytime you have to drop tab to retain control, you have some handling issue. Anyways, the owner of the Blackhawk was at Lake X having it dialed in. At this time Merc was already planning on closing the facility down so they sold him the props for a song. I too have wondered about the timing of the props. I wasn't sure if there was anything to be timed though. They counter rotate, so they will never be in phase, right? Something I'll bring up to Gary the next time I see him. Anyways, the cleavers above will never in time. The reason being is that the front prop is a 4 blade while the rear prop is a 5 blade.

Check out the pic below, notice the two bolts on the back cap? Do your drives have those bolts? I all but positive that my drive doesn't.

Airpacker

Cord, what are the props in the upper picture in your Last post?

Cord

iTrader: (2)

Those are some custom made Hoss chopper props. They're 27's, so they're a bit small for me. With the cup coming around the tip like that, these may just provide the bow lift you're missing. We'll see.

ST31

I have a set of BlackHawks on my 31SS Sonic. Since switching to the new gears I have had no problems. The boat runs great and I have no compliants, but you do have to learn how to manuver around the docks.

robyw1

In what way is it different? I would have thought it would have been a little easier.

Roby

OshkoshThunder

robyw1,

Since you have (2) counter-rotating props on each drive, when you put a BlackHawk in gear be ready. It moves forward in a hurry. On the other hand, you can really get some fast 'reverse' response when you need it. They do take getting used to, but it does not take much to tame them. That question brings up an interesting point. If carberated, your idle may need to be set higher than normal to handle the demand of the BlackHawk when going into gear. On most factory setups with the BlackHawk, EFI engines were used to compensate for the load associated when going into gear, and keep the motors from 'snubbing'.

Airpacker

But shifting the Hawk is like BANG!!!!!, I hate that part. It literally shudders my whole boat and usually elicits a comment or two from people around the dock. I installed a neutral safety switch override switch so i can fire it in gear.

Robyw1, my cat idles at approx 7 mph. Makes dock and trailer approaches very interesting to say the least

Cord

iTrader: (2)

I wasn't joking though when I said that my bh was shifting softer than the bravo. BUT! I had this ventilation thingy and I was trimming the drive up so the props were near the surface. Trimming up like that also seemed to kill the speed. If you guys wanted to experiment with my technique, it would be interesting to compare notes.

OshkoshThunder

Cord,

Right On. Trimming up does help slow the wake speed down. I have to pull one out of gear, or else trim up, but I don't like doing that to the universals. AP, my BH's shift nice and smooth - no bang. Not sure what's going on with yours. I also have EFI and small blocks, so I imagine the torque is a lot less. The EFI really does help smooth things out tho...

Airpacker

I wish I could lower the idle speed out of gear but my 500efi idles at 900 and thats that. Shift it and it hits hard.It wasn't ever programmed to have a Hawk on it so maybe thats the difference. I am going to play with more ventilation this winter,like a snorkel that extends above the water by a few more inches to see if that will soften thngs up alittle.