XTB-21 with 150 Pro-max looking for more.

[aaronmt]

My buddy has 89 xtb that were setting up, and looking for a bit more. He has a 96 150 promax ,svs system with a 10" cmc ,25 trophy and a bout 3/4" below the pad.It ran a very impressive 74.1 gps mph. We will be changing out the cmc for a 14" rapid jack and possibly a 26 chopper. What prop height should we go for? Has anyone ever got neer 80 with a 150 on these? This is a strong 150 but a 150 none the less. Aaron

 

[msethsmile]

A slight hassle, but change the stock tuner, which is a joke, to a 41914c merc. Also, the timing on a 150pm is 19 degrees, IMO also a joke. Standard 2.5 is 25 degrees @ WOT. I don't know that particular Allison but have owned that motor.

 

[aaronmt]

I beileve the tuner has been changed and we will varify the timeing .Any more ideas guys?

 

[ally2dextreme]

My buddy has 89 xtb that were setting up, and looking for a bit more. He has a 96 150 promax ,svs system with a 10" cmc ,25 trophy and a bout 3/4" below the pad.It ran a very impressive 74.1 gps mph. We will be changing out the cmc for a 14" rapid jack and possibly a 26 chopper. What prop height should we go for? Has anyone ever got neer 80 with a 150 on these? This is a strong 150 but a 150 none the less. Aaron

make sure you brace the rapid jack like the allison plate is and you could mill your heads for more power...i ran 83 with my 2.4 150 on my xb with a 30 hoss triton at even with the pad

 

[Fishforcash]

Cut your heads to 35CC and use .75MM Mercury HiPo gaskets. This should put your compression in the 140s and will still run on 93 octane pump fuel.

I wouldnt go any farther with the motor. For the price of a SVS and a ACU you would buy a 225 drop on powerhead.

 

[aaronmt]

Ya we agree totally , he has a acu as well as the svs. The plans are to do a promax , were just trying to see just how fast this lil 150 can push it. Any ideas on prop height with 14" setback.

 

[HO]

aaron,
The prop height will definitely depend on the prop. As you know, not all props are created equal...espescially when it comes to running a high engine. Depending on the pad condition (stock, blueprinted, no lip), with 14 in of setback you should theoretically be able to get water pressure pretty high on the jack. My XTB never really liked anything over even with the pad no matter how much horsepower, prop, or setback I had on the back. I could never find a prop to carry the front when I went higher than even.

My stock 2.4L 200 ran 83 with 3" setback and a worked over 28 (A5) chopper. I would think your 150 has more than a stock 2.4L 200.

 

[Fishforcash]

What gearcase?

Cone?

 

[aaronmt]

The only reason we put the svs on was becouse he had it laying around.The lower unit is a cle 1.87. Havent got the acu dialed in so it was faster with the stock computer.

 

[msethsmile]

Confusius: There is no such thing as a bad prop, only a bad application.

Part II: There is one thing better than cubes...and that's more cubes.

I've always had luck w/ mazco re3's and Hoss Triton 1's (but not on an xtb). I'm not sure a stock cle is the way to go on an Allison.

 

[Fishforcash]

I think it would run its best number with a stock torquemaster. Install the Merc SS scoops over the holes and it will run up higher. It should hold up to 80 easy and carry a load much better.

I bet the CLE is slowing you down because you dont have the torque to carry the bow at high propshaft heights.

 

[catfish123]

Get the motor up a little bit. 1/4 inch below to even and you should see some better numbers. Matt