ok, so in the last year i've made a few changes to mine... but now im ready to make some more. i did the imco box and steering, and the box has the 3" lift. the boat ran a reliable 65 on the gps before with the old motor and the stock exhaust with a 28p b1 at 4200 rpm's( dunno why, but it did run better than a 26 at 4600) now it runs 72-73 on the gps depending on the water conditions with a labbed 26 b1 at 5750 rpm's. the boat handles way better at all speeds, but it is real lazy out of the hole(mostly because i lost torque when i rebuilt the motor and went to a much larger cylinder head). i am thinking about going to a shorty lower now, and i also need to figure out what size trim tabs to run now. my stock bennet tabs work just fine mechanically, but have almost no effect when running. my boat rides on the last 2-3 feet of the pad at full throttle, and for the most part doesnt chine walk, but gets a bad porpoise if the water changes at all. im going to be adding a blower this winter, and i figure it should make in the 850-900 hp range when im done with it. any suggestions?

or should i just ?

thanks, glenn

With 900 Hp you’re going to need a serious drive. Look into Max Machine Works drives with an Imco lower unit. If you’re looking to get out of the hole quickly with 900 HP your going to blow drives, even with a modified drive. Just let it take its time.

It’s also probably taking a long time to plane off because of the shorter X dimension. Mine takes some time to plane off as well.

Running a 2" shortly on top of the 3" you already raised the drive you might be to high. You will only be 2 1/2" down. Be careful

It will get on plane better with a 5 blade prop, but the hull likes the 4 blade B1 over all for rough water handling and smoother ride. The B1 prop likes to throw a nice rooster tail as well. The hydro motives didn’t work well at all for me.


My boat will not chine walk but will porpus on calm water with the 5 blade maximums. No porpus with the 4 blade B1

I have 280 tabs on mine but want to switch to 380. I notice that if I keep the tabs level with the hull at WOT I get much better stability. With the 280's small tab adjustments do a lot to the boat.

I also sanded the bottom of the hull to help straighten it out and take out some hook. My hull is very wavy and has a lot of imperfection that need to be addressed. I hope to see some good gains when it all straight. The small amount for work I did already helped with the ride and speed. Check your hull with a 4' metal straight edge look for imperfections.

The boat has 820 HP. we hit 85 mph on GPS with 2 adults and 1/2 tank of gas, running a 30P B1 @ 5900 rpm

I think with a labed prop 32 B1 and the hull straight and lighter on fuel and the right condition, I like to think I should be close to 90.

Also with the speed you’re running and are looking to run I hope you have external steering.

Paul

So what kind of cubes and what kind of boost are you running to get those HP figures? I'm still less than 600hp with B&M 250's.

I'm hoping to get some work done on the engines in the next year or two and am always looking for suggestions. I run mild boost, but even if I turned it up, it would be tough to get more than about 775hp. Who built your engine(s)?

Frank D’Amico in Cohoes NY. D'Amico Custom Marine & Racing Engines. Well know by the local performance boaters in the Lake George NY area Excelant reputation.

Motor is 552 CI 8/71 blower with super chiller, aluminum heads , Made 820 Hp at 5600 rpm with 7 PSI boost.

i did do the dual ram hydraulic steering system when i added the box. the motor is is an 8.1:1 505 with a pfaff hydraulic roller and pfaff merlin heads. i built the motor with the intention of adding an m4 procharger, but i wanted to take baby steps before going ballistic. i ran a straight edge down the vee, and its perfectly straight. i ran the edge down the pad, and it has a 1/4"-5/16" hook at the tail edge of it. ive read alot of posts about the hook being placed there intentionally by the manufacturers, but im not sure if thats the case here. since im changing the lower, i think i may go ahead and just do the complete imco extreme. hot boat... my x dim. was 9 1/2" when i started this whole thing. the 3" box only raised the drive "theoretically" 3". after factoring in the angle of the transom, it really only brought it up about 2 1/4" from the bottom of the vee at the propshaft. i called dana marine and asked what they recommended for tabs, and they suggested the ht1100 tabs, which are 12"x30" long, but said they wanted to "kick" the tail edge up so they wouldnt drag. they also suggested to mount them parallel with the water line, rather than even with the transom. any thoughts here?

My factory prop shaft center line was 7 1/2 “. Yours sounds deep for some reason.

As for the tabs I thought about mounting them parallel with the water but decided to keep them where they are. There is a few post on the subject. I would be very interested on hearing how it works out. I can say that at slower speeds when I put the tabs down to keep the nose down, if one tab is lower than the other it will steer the boat in the other direction.

If I was looking for new tabs the 12 x 30 is what I would get

The hook in the hull is from the factory. Some 28 owners like my self have removed some or most of it with good results. The bottom of my hull is real wavy and needs work. I think that ware my high slip #'s are coming from. I am looking to re finish the bottom of the hull this fall.

Please keep me informed on how your project is going. I would love to here your results.

hot boat... sounds good. im going to go ahead and get the big tabs and try the parrallel mounting then. ill let you know what happens with that. i havent figured out why my drive was mounted so deep, but i checked the measurements twice because i wasnt sure. what kind of improvements did you notice when you flattened the hook out of your pad?

9 1/2" is stupid deep, that is just odd. I would think that once you add the 2" shorty you are about where I am with the stern jack I added at a slightly positive trim.

When I sanded the hook I noticed that the boat rides better and smoother at high speeds. Tom R said he gained some MPH. I have done so much to the hull at once I can’t tell if I gained speed or not, but I like the ride.

Remember that this hull was not designed to go as fast as we are pushing it. I just hope when I get the hull straight I will lower my slip #'s and gain some speed. My goal is to hit 90 mph. as far as I know no one has hit 90 with this hull. With the HP I have, I would think it should be possible. We will see.
Keep me posted, you have all winter to test and toon since you line in NV. I'll be snowmobiling all winter. It only helps pass the time by until spring.

hopefully with the new power and some of these other mods, i should be able to get there. my goal has always been 100. prolly a little unrealistic, but my goal nonetheless.