View Full Version : 90 + fly bye 21 ft phantom UK ls powered

06-21-2012, 12:01 PM
Here s a vid of my ls powered project ,got lot info here about the Blackhawk drive which is on on this run got it up to 6500 rpm and 95 mph on the gps which give me 20% slip
too much I think and afraid that I have it too high x dimension is set at the magical 17,5 " whit the underside of the bullet out of the water
I think the boat is not coming out enough but when I try to trim a bit more the props lose bite .
are there any experts out here ?


06-21-2012, 07:26 PM
The X is correct but the hull is staying too wet, BH's do not trim well no leverage. Looking at the boat it appears to have a goodly portion of its weight forward. You may be a candidate for Arneson rocker plates, they will give you the bow lift you need. IMO your RPM's are way high for the drive, But I feel your slip number will improve a lot once you get the hull loose. Back to the X, having the bullet in the water flow gives you stern lift which is the last thing you need. Your boat will need help to run its best, a 22 BH has rocker to get it loose, but the rocker can make the boat get hairy at times. When I had the BH on my 22 my slip numbers at cruise 45 mph were very low, at WOT they were way up. I am now running a Bravo X and run almost 3 mph less at the same cruise RPM.


06-24-2012, 06:08 AM
Hi Phil ,

that was a bit where I was afraid off when bought the BH because my hull needs bow lift but d not have a rocker in ,I hoped the power had pushed it hard enough .

Would a pair of rocker plates work on this setup ,due to the fact they are almost next to the drive and they are developed for the arneson drives which are a bit further away from the transom .

I was thinking to try a chopper prop as the rear on the BH maybe that will give a little more bow lift way it need and I have to get 31 if that will work to get the rpm down .



06-24-2012, 11:06 AM
When I set my 22 up for the BH I spent a very long time gathering as much info as possible, I also spoke with Geo the owner of Mighty Mouse. He and a few others that I was confident in their knowledge advised me to shift as much weight aft as possible. One of my best changes for speed was installing another fuel tank well aft, there is a marked difference in speed between using the aft tank and using the stock Donzi tank.

I do believe the rockers will make a lot of difference, they made a tremendous difference on the 18 Mighty I believe about 10 mph. Props will help some but I do not think a prop will get to your full potential.