Hey guys, help me out! I am having a new 15x8 aluminum 3/4 deck boat built. I am putting a 6.0 LS new build, bored 20 over, worked 317 heads, comp cam, and converted to a Quickfuel carb! I have a steal on either a Stinger 2.09 or an Ox Box 2.88. I can not decide which is a better choice for my boat. I plan on running a wide 3 blade prop. HELP! Oh yea, I am new to this forum and the airboat world! I accidentally posted this in the wrong forum earlier. :scratch: :scratch: :scratch: :banghead: :banghead: :banghead:
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Ugh! Box dilemma! HELP!
- Thread starter Beebo
- Start date
CarMotorBarge
Well-known member
What are the cam specs? What engine RPM do you plan to run at WOT? Are you stroking the engine? Are you using a wide blade or a super wide blade?
The engine isn't stroked and I plan on running an 82" JR or 82" JX. I plan on WOT around 5800-6000, but would like cruise RPM around 3000 or less. I'll do my best at reading this cam card, lol! Intake HYD .610 Exhaust HYD .617, duration @ .050 intake 223 exhaust 231, and a lobe separation of 112. Hope that makes since. Thanks again guys!
SWAMPHUNTER45
Well-known member
2.55 or 2.68 would be my choice
Aeon
Well-known member
2.09 is under and 2.88 is over. You won't have enough hp to spin the jx with the 2.09. At 5100 rpm the prop will be maxed out but to even get it that high you will have to take all the pitch out. With the 2.88 at 6k the prop is only at 2085 rpm. Leaving quite a bit of thrust.
2.55 or 2.68 but don't think either way you will have enough thump for a jx and not sure about the jr. As long as the motor is out i would put a stroker kit in it with fordged parts
2.55 or 2.68 but don't think either way you will have enough thump for a jx and not sure about the jr. As long as the motor is out i would put a stroker kit in it with fordged parts
SWAMPHUNTER45
Well-known member
To important of a component to make a poor decision. You would regret not matching the engine and prop to the optimum ratio drive.
In selecting the three components you first determine your engines operational range in rpm. You then select the prop and verify its operational range. You then work the math to determine the best ratio.
Example:
Engine peak 5700-6000
Prop range 2150-2300
Ratio:
2.55 X 2150 = 5482 engine rpm
2.68 X 2300 = 6164 engine rpm
This should allow you to consult with your engine builder and prop rep. and make a wise decision on the best ratio. If your using a wider blade and you seek to choke it back the 2.68 may prove to be better. If you have a lighter rig and seek a lower cruise rpm the 2.55 may be a better choice.
In either case my opinion is both would work better than your previously mentioned discounted ratios.
Hope it helps
In selecting the three components you first determine your engines operational range in rpm. You then select the prop and verify its operational range. You then work the math to determine the best ratio.
Example:
Engine peak 5700-6000
Prop range 2150-2300
Ratio:
2.55 X 2150 = 5482 engine rpm
2.68 X 2300 = 6164 engine rpm
This should allow you to consult with your engine builder and prop rep. and make a wise decision on the best ratio. If your using a wider blade and you seek to choke it back the 2.68 may prove to be better. If you have a lighter rig and seek a lower cruise rpm the 2.55 may be a better choice.
In either case my opinion is both would work better than your previously mentioned discounted ratios.
Hope it helps
SWAMPHUNTER45
Well-known member
Stinger and Ox offer a 2.55
Good luck with the build and let us know how things turn out.
Good luck with the build and let us know how things turn out.
CarMotorBarge
Well-known member
For that boat, motor, and cam combo, I would go with the 3 blade JX and 2.88 ratio. Here is why:
1. The 15x8 boat isn't particularly small. The 3 blade JX will push better than the JR. The JX is more of a tractor blade while the JR is sportier.
2. With that cam spec, you will make good HSP to over 6K RPMs.
3. The JX needs to spin about 2,100 RPMs at the prop. A 2.09 ratio would give you about 4,400 engine RPMs. This is way to low. A 2.88 ratio will give you 6,050 engine RPMs. This fits well with the cam spec. You will also have the flexibility to add or take out a little pitch because you will still be within the cam specs.
I doubt you will cruise at 3K RPMs with this combo. However, I wouldn't worry about that. Cruising 3200 to 3600 with the 2.88 ratio isn't hard on the motor. The 2.88 puts less load on the motor. It is better to put more RPM and less load on the engine.
Also I wouldn't assume that fuel mileage will be worse with the 2.88. The engine is actually more efficient at higher cruise RPMs. RPM is only one of several factors that effect fuel mileage.
I suggest stroking the motor. Also have you upgraded the valve springs and push rods? You have a higher lift cam.
1. The 15x8 boat isn't particularly small. The 3 blade JX will push better than the JR. The JX is more of a tractor blade while the JR is sportier.
2. With that cam spec, you will make good HSP to over 6K RPMs.
3. The JX needs to spin about 2,100 RPMs at the prop. A 2.09 ratio would give you about 4,400 engine RPMs. This is way to low. A 2.88 ratio will give you 6,050 engine RPMs. This fits well with the cam spec. You will also have the flexibility to add or take out a little pitch because you will still be within the cam specs.
I doubt you will cruise at 3K RPMs with this combo. However, I wouldn't worry about that. Cruising 3200 to 3600 with the 2.88 ratio isn't hard on the motor. The 2.88 puts less load on the motor. It is better to put more RPM and less load on the engine.
Also I wouldn't assume that fuel mileage will be worse with the 2.88. The engine is actually more efficient at higher cruise RPMs. RPM is only one of several factors that effect fuel mileage.
I suggest stroking the motor. Also have you upgraded the valve springs and push rods? You have a higher lift cam.
CarMotorBarge
Well-known member
That motor with a proper tune should make around 500 HSP pretty easy. Estimating 425 HSP is low.
Also I would not go with the 2.55. It isn't enough gear ratio. The prop speed will be too high. 2.68 at the minimum.
Also I would not go with the 2.55. It isn't enough gear ratio. The prop speed will be too high. 2.68 at the minimum.
SWAMPHUNTER45
Well-known member
2.68 drives are a very common ratio for SBC and LS. All the companies offer a 2.68 ratio.
If considering Sensenich give Darrin a call he has a large data base with years of experience and can give solid advice on a specific combination. He may steer you to the 2.88 worth a call to discuss it with him.
Use all the analytical data you can get in making a decision. Do the math, talk to the prop folks and your engine builder. In the end when you get two or three ratios that look good it's what make you happy for the type of riding you want to do, your satisfaction is what matters.
If considering Sensenich give Darrin a call he has a large data base with years of experience and can give solid advice on a specific combination. He may steer you to the 2.88 worth a call to discuss it with him.
Use all the analytical data you can get in making a decision. Do the math, talk to the prop folks and your engine builder. In the end when you get two or three ratios that look good it's what make you happy for the type of riding you want to do, your satisfaction is what matters.
CarMotorBarge
Well-known member
Beebo said:
A little more RPM at cruise isn't necessarily bad for longevity. A higher gear ratio takes load off the motor and decreases the chances of detonation. Both of these help with longevity.
I have run a 2.68 and a 2.88 with a 4 blade R. The power requirements of a 4 blade R are very similar to a 3 blade JX. I cruise at higher RPMs with the 2.88 than the 2.68, but the 2.88 makes more thrust and gets a little better fuel mileage.
However if you end up going with a 3 blade JR, I would recommend a 2.68 because you need to get the prop RPMs higher to get similar thrust.
Did you put cast or forged pistons in the engine? Cast pistons are more brittle and less resistant to detonation than forged. Also did you upgrade the rods and rod bolts? I would also recommend running recessed spark plugs to decrease the chances of detonation.
CarMotorBarge
Well-known member
Sounds like you have a nice engine. Hope you enjoy it. 8)
One Eyed Gator
Well-known member
I definitely would not go with the 2.09. I can't comment on the 2.88 never had one.
I run a 6.0 iron block stock bottom end with a much lower lift cam but a little more duration (GM ASA Cam), has 706 heads worked with 2.00" stock valves ( heads bump the lq4 stock compression to around 10.5 )with matched springs and better pushrods. Motor is pushed a 79-1/2" 3 bld R at 14.5 degrees through a 2.68 stinger turns 5,500 and cruises at 3,200 and loaded for fishing 3 guys it like 3,400.
Boat is a 98' 14x7-6 beat-up old alumitec with stainless rigged front driver double rear.
Runs fairly well for a budget build.
Good luck
I run a 6.0 iron block stock bottom end with a much lower lift cam but a little more duration (GM ASA Cam), has 706 heads worked with 2.00" stock valves ( heads bump the lq4 stock compression to around 10.5 )with matched springs and better pushrods. Motor is pushed a 79-1/2" 3 bld R at 14.5 degrees through a 2.68 stinger turns 5,500 and cruises at 3,200 and loaded for fishing 3 guys it like 3,400.
Boat is a 98' 14x7-6 beat-up old alumitec with stainless rigged front driver double rear.
Runs fairly well for a budget build.
Good luck
