Motor Height & Porpusing Question

[firekracker50]

I can run in the 70s with no roster tail, and what i think is very little neg or close to level trim. But i dont have a trim guage. But to gain speed i have to trim a little more. I can run to low 80s with a little tail but the boat porpuses really bad.
If i trim above that point the porpusing is better and i can run the same speed, but the back of the boat starts to want to skip around.

I have ran this boat and others setup differently to low-mid 90s so i know how to drive a boat. But i am scared to push it much past 80 with it handling like it is.

I dont know whether i should raise the jackplate because the rooster tail is so small, or whether i should lower it and use more trim.

Any suggestions would be great
Thanks

[Props4u2]

What boat are you running?

[firekracker50]

Well ur probably not going to be familiar with the hull. But i though a general rule of thumb on allisons would apply.

The Boat is a Stratos 20XL Velocity (900# Kevlar Hull Weight). It was built by al stienson who worked for paul allison for 10 yrs.

The pad is very similar to an allison's but...
The allison pad is open air beween the edge of the pad and the first strakes just a few inches to each side of the pad.
My stratos is the same profile as the allison pad, but the pad continues and is solid to the edge and rolls into the firsts strakes. So the pad is all in all a couple inches wider on each side of the pad. So it lifts with weight better than an allison, but does have slightly more drag in the water.
Driving the boat it is very similar to an allison but it doesnt tilt to one side and ride there. You constantly have to battle to keep it on the center of the rounded pad that i described.

I have a 10" Offsetter Jackplate. And a Mod Merc 2.5 (285HP) with 15" Single Ram Mid, and a 1.87 Sporty lower. I am running a 28" Hoss Cut Chopper by Hydromotive.

[Props4u2]

If that's the same model Stratos built 5 or 6 years ago I must say it was the worse handling boat I have ever driven, you had to use much more trim than I was comfortable with to make it take a set. It would porpoise and get the rub rail wet in a 20 to 30 mph sweeping turn. Enough on that. Usually when the rear wants to act like it's on banana peelings the engine is too low and the prop is trying to walk to the surface or you're not useing enough positive trim so the water is hitting the lower unit at the wrong angle which makes the unit act like a ski and try to come to the surface. You could try adding weight to the front of the boat which in turn will allow you to use more positive trim to see if that's the problem.
The above is just my opinion, test at your own risk and be careful.

[firekracker50]

Thanks fir the reply.
My boat was the prototype built prior to the ASX boats that you are talking about. THose boats were 1450lbs.
My rigis 900# Hull weight and is entirely kevlar, there is no fiberglass or wood. My boat is the only one of its kind. Its called the 20XL Velocity. I dont know why they never produced it. The techs from stratos told me they had it over 100MPH with an evinrude on it. But i dont know that i believe that. I dont see how the gearcase didnt blowout at that speed.

I dont know how my hull or handling compares to the ASX. I have never driven one.

If i use hardly any negative trim the motor almost drowns, cant breath and the holeshot is horrid. If i trim up to about level trim it comes right out of the hole. The motor will turn up RPMs coming out of the hole as fast as the motor will when out of the water hooked to a garden hose. But the motor does lag around the 3500RPM range for a half or 1 sec even when on the hose. And then ramps right up.
So i put a pin in the highest hole in the mid so that when trimmed all the way down its barely below level trim.
Also my motor was set 2" below pad. I raised it to 1.5" below.

This seems deep to me because my bullet ran 2.5" above with a TXP-OT4. But i dont know. I just started at 2" below because my buddies allison is set at 1.5" below. So i thought i would start there and work up.

I was going to run the boat tonight but i has some water temp issues monday night so i was going to replace the thermostats with 1/8" fender washer. But i didnt get them installed untill 1hr before dark. The thermostats dont begin opening till about 170deg and dont full open will close to 180deg. And one never fully opens. I think i need new thermostats.

I really appreciate all the help!
I'll run the boat over the next few days and see what i find out.
Again thank you so much for the advice.

[Props4u2]

Yep, the ASX is the one I was talking about. Getting old is no fun!

Good luck and be careful.

[Darth VMAX]

I thought you sold this boat and got a Cobra? Or do you have both of them?

[firekracker50]

Yeah i have both. I sold my Bullet. I have owned allot of boats in the last few years.
I am selling the Stratos as much as i am going to regret it. But i just cant aford to keep 2 boats.

[firekracker50]

I took it up a half inch. Went for a run and it handled much better the first run. Not nearly the porpusing and went right to 85 and was climbing. But wanted to fall off pad real bad. And i didnt feel like the nose as flying really high. Maybe it wil just feel different and not run as high with this motor.

But the second run i took the boat would never stop porpusing. Upand down on the trim hd no effect. I would give gas and let off gas and it just kep porpusing al the way to 75MPH and then i gave up. It was getting too dark anyways.

[Slow Hand]

"If that's the same model Stratos built 5 or 6 years ago I must say it was the worse handling boat I have ever driven, you had to use much more trim than I was comfortable with to make it take a set. It would porpoise and get the rub rail wet in a 20 to 30 mph sweeping turn."

Ouch! I love the way my ASX handles!

[Props4u2]

Slow Hand,
If it works for you that's all that matters.