My Outrageous STV Project

[cali kid]

Just finishing my 3 litre STV project. I was not sure if the boat could handle the big motor, but so far so good. I've only got 3 hours on the motor so i'm keeping it under 5500rpm. She runs from 80 past 100 pretty quick. Got a couple pics to share if anyone is interested.

[cali kid]

Should be. Will dyno it after I get a little more time on it .

[RBT]

3.4?
What did you do?

[cali kid]

3.4?
What did you do?
Stroker crank,.40 overbore,porting,carbon reeds,high compression,light flyweel,bigbore intake,special reedplate,56psi. fuel,special injectors,drystack,exhaust tuner,balanced,1.62 sporty,34" lighting et.and more.

[afr]

subscribed

[Instigator]

subscribed
ditto

[RB in NM]

Who did your motor work and what about fuel management? Interesting...........

[2.5_stoker]

cool project...cant wait to hear the dyno numbers

[cali kid]

Who did your motor work and what about fuel management? Interesting...........The ECU is motorola 555 from a 496 ho v8.Basiclly a core.Eric Simon did the program.The VST is from an early Opi as well as the hi pressure pump.I modified the vst to flow fuel from the float tank directly to the pump chamber.Lo pressure is holley red in the boat.The fuel rail is modified stock efi merc.The pressure reg and injectors are from Marren in Conn.All the fittings and hose are Areoquip socketless 6 AN.I did all the motor work myself.

[dnr78]

looks this should be insane
im watchin

[afr]

lets see its stance sitting in the water got any pics of it wet

[RussF]

looks this should be insane
im watchin

:eek:

[cali kid]

lets see its stance sitting in the water got any pics of it wetIt doesn't set much lower than it did with the BP on it.We took a Flip camera with us over the week end.I'll try to put some of it on here.

[cali kid]

I ran the boat over the weekend.Got a Livorsi 120 GPS tattle tale speedo. Very close to pegging it with a 200 pound passenger. Ran around 115 solo and got a scary speed wobble. It's stable with 2 people. Still have the rubber mounts in it.Got solids coming this week. Using sea star pro steering,feels pretty tight. Any thoughts or suggestions? Thanks

[Fl Boy in ILL]

Yes be very careful and wear a good jacket

[hydrostream1]

I would like to see it in the water,looks a 20 in mid.I just bought a stv,I'm thinking of putting my 300xs on it off my cougar,just to try it.

[njj502]

Scribed

[afr]

I ran the boat over the weekend.Got a Livorsi 120 GPS tattle tale speedo. Very close to pegging it with a 200 pound passenger. Ran around 115 solo and got a scary speed wobble. It's stable with 2 people. Still have the rubber mounts in it.Got solids coming this week. Using sea star pro steering,feels pretty tight. Any thoughts or suggestions? Thanks
sweet watch your ass whats with the rider

[STV_Keith]

Ran around 115 solo and got a scary speed wobble. It's stable with 2 people.

Did it start dipping sponsons left to right...kinda like a chine walk? The boat is setup with starboard side steer, right? Next time, lean your body (above the seat) over towards the center of the boat. My PCS does this at about 103-105 and leaning over moves enough weight towards the center for it to stabilze. Doesn't do it with a passenger.

[cali kid]

Did it start dipping sponsons left to right...kinda like a chine walk? The boat is setup with starboard side steer, right? Next time, lean your body (above the seat) over towards the center of the boat. My PCS does this at about 103-105 and leaning over moves enough weight towards the center for it to stabilze. Doesn't do it with a passenger.Yea we got the same boat.Exactly like a chine walk.Do you stay towards the center through out your run? ~ Randy

[cali kid]

Yea 20" mid.You might like it.What stv you got? ~ Randy

[cali kid]

As requested, here are a couple more pictures of the STV.

[keane]

It doesn't sit as low as I thought it might. Mine sits that low with a 280 and 6 inches of setback.

[afr]

It doesn't sit as low as I thought it might. Mine sits that low with a 280 and 6 inches of setback.
lloks good i thought it would be way way lower then that
i want to put a 3 liter on my hst when i get it ready

[Hoss Marine Propellers]

Subscribed..... Yeah Baby!!!!!

[cali kid]

Thanks guys. Thats with 28 gallons hi test. I ran it with a Hydromotive Quad IV 28" over the 4th. Acceleration is " Staggering" Still I'm shure there is a better prop. ~ Randy

[WATERWINGS]

subscribed also....

[STV_Keith]

Yea we got the same boat.Exactly like a chine walk.Do you stay towards the center through out your run? ~ Randy

Once I hit 100, I usually move over in anticipation, and stay there 'til the end of that run if I'm solo.

[21tinymessere]

subscribed also!!

[Hoss Marine Propellers]

Stroker crank,.40 overbore,porting,carbon reeds,high compression,light flyweel,bigbore intake,special reedplate,56psi. fuel,special injectors,drystack,exhaust tuner,balanced,1.62 sporty,34" lighting et.and more.


What kind of RPM are you wanting/planning to turn the motor?????? :confused:
That way, we can all figure up a "theoretical" speed !!!!!!!! 1.62 gear with 34" pitch !!!!!!
Engine should definitely have the guts/torque to swing a big wheel!
Look forward to seeing some impressive numbers!.......

ps. I think everyone that subscribed, including myself, is living vicariously through you right now..... we all what to see how fast "WE" can run in your boat !!!!!!!!!! hehe :eek: :D

[cali kid]

What kind of RPM are you wanting/planning to turn the motor?????? :confused:
That way, we can all figure up a "theoretical" speed !!!!!!!! 1.62 gear with 34" pitch !!!!!!
Engine should definitely have the guts/torque to swing a big wheel!
Look forward to seeing some impressive numbers!.......

ps. I think everyone that subscribed, including myself, is living vicariously through you right now..... we all what to see how fast "WE" can run in your boat !!!!!!!!!! hehe :eek: :D 7200 Peak power.What kind of speed we lookin? Maybe I'll buy one of your Props.What have you got? or suggest ~ Randy

[Hoss Marine Propellers]

7200 Peak power.What kind of speed we lookin? Maybe I'll buy one of your Props.What have you got? or suggest ~ Randy

OK... here we go.... this gets discussed quite often... It's just theoretical & not a real number (Because of alot of reasons- errors?)

7200 rpm with 1.62 gears & 34" pitch prop = theoretical speed, no slip of 143 mph.
5% slip = 136 mph
10% slip = 128.7 mph

Just gives you a range of speeds to look at .........
When you get running that fast, "drag" is terrible and translates into slip........
Increase HP to overcome drag or reduce "slippage" to run more efficient & faster.

If the 34" doesn't seem to be enough, we've been know to have built a few 35"s & one 36" pitch Triton, back in the day????
Just the thought of one revolution and moving 3 feet in the water? WOW!!!!

[cali kid]

Hey Tim,Thanks for your calculation.I'm pretty shure the boat is capable of high 130s.I don't have the set up right enough to try those speeds yet.Blow over is not an option! The 34 seems to make alot of bow lift.I think I might be looking for something that doesn't lift the boat so much.Maybe a cleaver style.What do you think? ~ Randy

[Hoss Marine Propellers]

Hey Tim,Thanks for your calculation.I'm pretty shure the boat is capable of high 130s.I don't have the set up right enough to try those speeds yet.Blow over is not an option! The 34 seems to make alot of bow lift.I think I might be looking for something that doesn't lift the boat so much.Maybe a cleaver style.What do you think? ~ Randy

I agree with "capable of high 130's" statement.

When people say "cleaver style", what they are really saying is a lower rake prop..... Most cleavers are lower rake compared to a chopper style which is considered high rake....... low rake is stern lift & high rake is bow lift..... so, if you have too much bow lift, either go to a lower rake prop, typically a cleaver (or Hoss Triton 1), or raise the engine & surface the prop which keeps the prop from having the "leverage" to lift the bow...... When you start dialing it in, be very carefull.... the prop still needs to "bite" to keep pushing the boat forward..... You don't want too much torque on the steering wheel, which makes you "crab" the gearcase slightly instead of forward thrust .... You also do NOT want to "blowout"!!

When you get close to getting it dialed in, there are so many little things that need to be addressed????

[MercNuts]

No way I'm running high 130's with a stock gearcase & skeg. I cant imagine what blowout would be like at high 130's and that would be nothing compared to losing a skeg. If you have that kind of power and plan on using it time to step up to a number 4 Speedmaster.

[milkdud]

An over the hub cleaver would my first choice. It will try to lift the rear of the boat up and make it lighter on the water and let the natural aerodynamics of the boat create the lift.

Your way out of my league, have fun be safe.

MercNuts. How fast has a stock lower unit been pushed?

Conrad

[Adam McKeon]

I had a similar set up and can tell you my rig did NOT like a cleaver of 3 or 4 blades... Crabbed like hell, broke loose a few times on the big end, and very flighty. As Tim said, you need bite to hold everything together. I will say this, I spent ALOT of money dialing in that prop that did work. Mainly from hitting the stock limiter over and over again. I did not have as much HP as you may have so I only got mid 120's but I thought that was very fair for a new motor with warranty :) Interested in your Dyno findings...

[cali kid]

No way I'm running high 130's with a stock gearcase & skeg. I cant imagine what blowout would be like at high 130's and that would be nothing compared to losing a skeg. If you have that kind of power and plan on using it time to step up to a number 4 Speedmaster. Is a fat shaft sportmaster considered a stock gearcase? The skeg and torque tab are massive.

[cali kid]

Can you tell me more about your boat and motor? What prop and pitch did you end up with? Thanks ~ Randy

[STV_Keith]

Might want to consider a low-rake round ear. I'm partial to the Mazco RE-3's myself. The 27's and 29 I have are all about 15-17* of rake so not as much bow lift, but lots of blade area at the tip for good bite and slip numbers. At 112mph, my PCS turning 8700rpm through 1.87 gears with a 27 Mazco RE-3 is putting up a slip of about 6%.

[cali kid]

Might want to consider a low-rake round ear. I'm partial to the Mazco RE-3's myself. The 27's and 29 I have are all about 15-17* of rake so not as much bow lift, but lots of blade area at the tip for good bite and slip numbers. At 112mph, my PCS turning 8700rpm through 1.87 gears with a 27 Mazco RE-3 is putting up a slip of about 6%. Thanks for the suggestion.I was running a 28 Mazco RE-3 With the BP I had on the boat before this motor.Too bad it wont work with the fat shaft.I'll start looking. ~ Randy

[milkdud]

I had a similar set up and can tell you my rig did NOT like a cleaver of 3 or 4 blades... Crabbed like hell, broke loose a few times on the big end, and very flighty.

Adam how was a cleaver make you flighty? A cleaver should naturally be less flighty.

I can understand it walking the rear of the boat around crabbing, but your going to get that with most props unless you address it.

FYI I have not forgotten about SML. Are you back in SML late this year again?

Thanks
Conrad

[cali kid]

As requested, here are a couple more pictures of the STV.
I,m bumping this post for the pics

[ProComp]

I,m bumping this post for the pics

how about some performance feedback?

[cali kid]

I recently Installed a Hydromotive QV OT 31" pitch on the boat. The scary bow lift is gone, and I'm carefully pushing the envelope. It's just a river rocket, I'm not into drag racing. The acceleration is phenomenal to say the least. I'm running it over the weekend, I'll see if I can get my go pro to work and post some video. Thanks for the interest.

[AZMIDLYF]

subbed

[R.grover]

Did you dyno it yet?

[cali kid]

Did you dyno it yet?
No, the closest dyno is about 100 miles away. Have not had a chance yet.

[capteliminator]

Sweet boat cali kid!!! Be safe and keep us updated on your performance!!!

[whipper]

Did it start dipping sponsons left to right...kinda like a chine walk? The boat is setup with starboard side steer, right? Next time, lean your body (above the seat) over towards the center of the boat. My PCS does this at about 103-105 and leaning over moves enough weight towards the center for it to stabilze. Doesn't do it with a passenger.

Awesome project be safe as im sure you realize.;) Im not a tunnel driver but to me this would indicate the need to balance the hull port with a 30-40 lb shot bag when running solo. What i did for balancing my Allison was move my seat base side ways. now I have port/ left to starboard/right ability for weight transfer. I mounted it were I always drive so no need for fore and aft since im the only one driving her anyway. Solo I move the seat to the port and with a passenger I simply slide the seat the other way. At first it was a little weird having the wheel slightly over but now I actually dont even notice it. Quick way to see if you need to balance the hull solo is just add 40lbs in the port gunnel and take her for a dig. Couple of dumbbells like a 20 and two 10,s. that way you can take out 10 or both 10,s if 20 works? If that works you can get the lead shot bags made up in the desired weight once ya know what works.

Just a suggestion because hanging over to one side wouldn't appeal to me at 120. haha Any way thats what all the Allison boats need to do that arnt Center Steer to get the balance right. Its very critical at speed to prevent chine walk. When ya get the ballance right even Allisons are way easier to drive. haha Guys will use what they have on board to off set as much as possible to minimize the added weight. So battery over on the port side as much as possible ect.. Sick setup Calikid!! Im drowling!!:cheers:

[cali kid]

Awesome project be safe as im sure you realize.;) Im not a tunnel driver but to me this would indicate the need to balance the hull port with a 30-40 lb shot bag when running solo. What i did for balancing my Allison was move my seat base side ways. now I have port/ left to starboard/right ability for weight transfer. I mounted it were I always drive so no need for fore and aft since im the only one driving her anyway. Solo I move the seat to the port and with a passenger I simply slide the seat the other way. At first it was a little weird having the wheel slightly over but now I actually dont even notice it. Quick way to see if you need to balance the hull solo is just add 40lbs in the port gunnel and take her for a dig. Couple of dumbbells like a 20 and two 10,s. that way you can take out 10 or both 10,s if 20 works? If that works you can get the lead shot bags made up in the desired weight once ya know what works.

Just a suggestion because hanging over to one side wouldn't appeal to me at 120. haha Any way thats what all the Allison boats need to do that arnt Center Steer to get the balance right. Its very critical at speed to prevent chine walk. When ya get the ballance right even Allisons are way easier to drive. haha Guys will use what they have on board to off set as much as possible to minimize the added weight. So battery over on the port side as much as possible ect.. Sick setup Calikid!! Im drowling!!:cheers:
Thanks for the input. I'm using a heavy group 27 battery on the port side now. Really helped stabilize the ride. Appreciate the comments.