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Results from speed test with new Express Tube......

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goldnrod24

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Got out on the water yesterday with a GPS device.

Here are the results.............

2 -25" tubes, Merc 115 4 stroke, stock alum. prop 13 pitch, driver alone, 1/2 tank fuel, top up but stowed = 28 mph on GPS at 6400 rpm.

With Express Tube, 15 pitch prop, driver and one passenger, 1/2 tank fuel, top up but stowed = 28 mph on GPS at about 6100 rpm.

Now, I will say that I never expected this boat to become a speed devil and I went with the Express Tube to increase passenger capacity (I gained 2 additional legal passengers) and gain a better ride. Both of these expectations have been exceeded.

The speed thing still puzzles me though since I have the nose cones well out of the water. Spray from the tubes at speed is coming off the tubes at the helm (about halfway back). I am able to trim up way further than before, too.

So, the motor is one hole down from the top. A buddy who has ridden on the boat since the Express Tube was added thinks the lever effect of more flotation in the bow has driven the motor deeper into the water. He thinks it's now too low. I think I'll raise the motor to the top hole and re-test.

All inputs welcome!
 
Did you stay with an aluminum prop or go to SS?
 
Do your outer tubes have strakes on them?  I got 35 mph with a Black Max prop and 30 mph (but a lot more torque) from a Spit Fire on my 115.  Both were 15 inch pitch.
 
No strakes on the outside tubes.
 
Your numbers say adding the Express doesn't get you extra top end speed because the additional weight of the third tube negates that gain.  But, looks like you used two different props, so it is hard to make that claim with certainty.  Did you happen to try the same prop before and after the Express was added?

You got the benefits that you bought the Express for, so it was very worth it!
 
kaydano said:
Your numbers say adding the Express doesn't get you extra top end speed because the additional weight of the third tube negates that gain.  But, looks like you used two different props, so it is hard to make that claim with certainty.  Did you happen to try the same prop before and after the Express was added?

You got the benefits that you bought the Express for, so it was very worth it!
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I did run the boat with the ET and the 13 pitch prop. It spun too high of rpms and cavitated too much to my liking.
 
As we have spoken GoldenRod, I am more interested in increased passanger capacity and the quality of the ride rather than WOT speed.  Flat out question - Are you happy you spent the money?
 
Last edited by a moderator:
Link said:
As we have spoken GoldenRod, I am more interested in increased passanger capacity and the quality of the ride rather than WOT speed.  Flat out question - Are you happy you spent the money?
Click to expand...
Mark, I am happier than a pig in poop!
 
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