PDA

View Full Version : Blackhawk finally gets to 80 MPH !



Greg Maier
09-26-2002, 05:59 PM
80.1 MPH GPS to be exact. It was the combination of me learning how to drive her plus the 31 pitch props that pushed me past 80. Conditions were 65 degrees, raining, 1 ft chop, 1 person and a half tank of fuel. K-planes were all the way up, drive was trimmed way up, and she rode perfectly. She has a stock 502MAG. My next goal will be 85 mph, which I will hopefully reach with stainless headers.

Donzi Blackhawk
09-26-2002, 06:55 PM
Excellent!!! A true moment to be happy! I have always said that a Blackhawk must be driven, sometimes on the ragged edge. Just a note of input. When adding headers, try to go with the full tubed headers, over the cast. The tubes are tuned for better performance. I am running Stainless Marine headers on my Blackhawk, still breaking in the engine so I have not seen any wide open speeds yet. Another thing not forget is the flame arrestor. I am running a K&N on mine and should prove to work out well.

Bryant

Greg Maier
09-26-2002, 07:56 PM
Bryant,
Does Stainless Marine make a full tubed header? I looked on their web site and it looks like all of their systems use a manifold.

KMLFAMILY
09-26-2002, 09:24 PM
Congrat"s ! Did ya happen to glance at the tach reading ?

blackhawk
09-26-2002, 09:28 PM
Congrats Greg! You've got me beat by 1.5 mph.

BigGrizzly
09-27-2002, 01:31 AM
Greg,Stainless doesn't make full tube hedders. I have a set of CMIs on my Corsican and they are great. For your boatthey will cost about $8,000. The truth is on your application you won't realize the potential of them. I have spent some extensive time testing and beleive me on the dyno Stainless Marine and CMI (all stainless) elbow tops will give you the best bang for the bucks! Example a 572 big block marine motor 739 HP will lose 15 Hp if the full tube hedders are changed to Elbow tops and you will lose 4 Lbs of torque. Just did this at 6 pm tonight. Is it worth the added $6.000(except for the way-cool factor). The Dyno sheet is still on the seat of my car. My own boat has old Harding hp1000 cast alumimum hedders and my boat does Ok as for speed. Congrats on the speed I know how hard it is to get that speed. Fun isn't it!

Greg Maier
09-27-2002, 06:30 AM
KLM,
The engine was turning 4900 rpms at 80.1 mph.

Tom Davis
09-27-2002, 11:25 AM
Are you trying to go from 80.1mph to 85mph by just changing the exhaust??? If you do the horse power calculations, providing that exhaust is the only change, I don't think you will get enough horse power increase to get you the +5mph you are looking for. But its not a bad place to start. Just my .02

Woodsy
09-27-2002, 11:33 AM
Greg...

Congrats on making it to the 80mph club! Hopefully I will get there soon...

Exhaust isn't going to get you to 85... the HP increase is exponential relative to the speed. You would need a minumun of about 75-100hp to get those extra 5mph. Nothing that can't be gained by some motor work... aluminum heads, exhaust, cam etc...

Woodsy Von Donzi

96blackhawk502
09-27-2002, 10:51 PM
I just recently got a Blackhawk. Its in the shop right now getting tuned up. the engine is new so I havnt been able to do WOT runs yet, but I have been pushing it to aaround 65MPH tops. When I run the tabs all the way up it porpouses. Whats the trick?

Kevin

Bad-Tat
09-28-2002, 03:59 AM
96Blackhawk,
I found that leaving the drive vertical and dragging tabs until way up in the 70's reduces the porposing a lot. Also put a tab switch (ala Blackhawk) up on the throttle handle for fast access to dump the tabs when it does porpose. If the bow gets too high the stern will try and pass it up from underneath and you are in real trouble fast!! Ask Roadtrip about that feeling! Have pulled 78 with serious tabs dragging in 1.5-2' chop 2 up. Just have to have lots of room and raise the tabs slow. When water conditions change be fast on the tab switch!

Greg Maier
09-28-2002, 07:16 AM
Kevin,
First off, which K-Planes do you have? I bought my Blackhawk with the 280's, but I think it originally came with the smaller K-Planes. A few of the Blackhawks here have the 280's and the concensus is that they control the purposing better. When I was considering buying the Blackhawk, my Brother called down to Donzi to talk to a guy he knows down there who helped design the rocker hull. His name escapes me, but I could find out. He bluntly said that the boat rides like $hit below 65 mph and really starts to come into its own at 65 and above. I find his comments to be true. You need to constantly be adjusting the tabs when you are changing speeds below 65. Anything above 65 and my tabs are all the way up. Also, the tilt of the drive can create purposing. When the drive is in the fully down position, sternlift is created (I believe), which keeps the bow down and keeps it from purposing. When you start to trim up, the sternlift goes away, and the bow starts to come up. What I am saying is that it is not only the tabs, but also the drive that has to be adjusted to keep from purposing.

96blackhawk502
09-28-2002, 09:53 PM
wbateman, you bought your blackhawk on ebay didnt you? You outbidded me by like $100!! Oh well. Do you have any pictures of you Trim buttons on the throttle?

Keivn

Bad-Tat
09-28-2002, 10:47 PM
Kevin,
Neither of us made the reserve on E-bay for that one. I talked him down after it closed. It was the one in Phoenix. (Bad-puddy-tat) Will have to take a pix when I get home in a couple of weeks. For now it is a temp setup with an 0n-off-0n mini switch. Blackhawk put two push buttons in his. I plan on putting the mini switch inside the top plate of the handle with the toggle pointing towards the front. Have some 24 guage bundled wire that I have to thread down the inside of the handle this winter. I don't have the 280 tabs yet. Currently they are the 150's. The avitar was taken my second time driving the boat and hadn't figured out the drag the tab thing. That bow really does get up there!!!

Greg Maier
09-29-2002, 07:12 AM
My plan is to put in a gaffrig two handle throttle. I've bought it but haven't installed it. It has four switches on it. One for each tab independantly, one for both tabs at the same time, and one for drive trim. All of the buttons are within reach when my hand is on the throttle.