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Express Tube retrofit - raised my motor one hole, still no speed increase

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goldnrod24

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Some of you are following my Express Tube retrofit. Earlier, I posted how much I love the improved ride of a planing hull, but that my top speed, even with a different prop (13 to 15 pitch), is exactly the same as before the install.

A buddy observed that it seems the motor is too deep in the water. Saturday, I raised it one hole (now in the 3rd hole from the top). I can tell that there's some performance improvement, but it is just on the border of cavitating (in fact, I have to trim down to execute a turn) so no more raising for me.

Speed remains at 28.

Top rpms at WOT is 6100. The max upper range, according the the Merc manual is 62-6400. It revved too high with the 13 pitch prop. I'm not aware of a 14 pitch prop and I'm not especially interested in having one of my props re-pitched.

The final test for me is how the boat performs loaded with passengers. I'm not looking for speed, just to be sure it doesn't cavitate with the bow loaded down with people.

I know this isn't a high performance boat, but I sure was hoping to hit 30 mph with the new setup.
 
14 pitch would be an Enertia.
 
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Yikes!
 
I can hit 30 GPS with mine pretty easily.  Motor mounted all the way down (top hole).  It's perfect IMO.  I can have 11 people on board with coolers and dogs and still hit 20 WOT, and be able to cruise at 15 in the low 4k RPM range.  I've pulled a tube with 7 on board and am still able to pull at around 21-23, the boat doesn't even feel the tube.  It's in for the 20 hour service now, can't wait to pick it back up tomorrow!
 
McZiggy said:
I can hit 30 GPS with mine pretty easily.  Motor mounted all the way down (top hole).  It's perfect IMO.  I can have 11 people on board with coolers and dogs and still hit 20 WOT, and be able to cruise at 15 in the low 4k RPM range.  I've pulled a tube with 7 on board and am still able to pull at around 21-23, the boat doesn't even feel the tube.  It's in for the 20 hour service now, can't wait to pick it back up tomorrow!
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What pitch/type prop are you running?
 
There always seems to be quite a difference in WOT between the S and the R models.  Goldenrod, I just had my toons clean and with the two toons my WOT is 26
 
goldnrod24 said:
What pitch/type prop are you running?
Click to expand...
I've got the Yamaha Pontoon Performance SS prop. 14x13.  In 2' white caps with the bimini down and about 380lb in people we ran 29.5 at 5600 rpm this past weekend.  20mph wind gusts.
 
Link said:
There always seems to be quite a difference in WOT between the S and the R models.  Goldenrod, I just had my toons clean and with the two toons my WOT is 26
Click to expand...
I do wonder what the weight difference is between an S and R model.
 
There's a difference in weight.  You can read the specs online.

And the Enertia prop is probably the best addition to get yourself to your goal.  JacosMarine.com sells them for $469.
 
Bamaman said:
There's a difference in weight.  You can read the specs online.

And the Enertia prop is probably the best addition to get yourself to your goal.  JacosMarine.com sells them for $469.
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According to the 2014 brochure: Both 22' boats w/o motor

R Series with Express = 2384#

S Series with Express = 2456#

Hmmm.....
 
Now that surprises me, was it the same floorplan?
 
On the water now for the first time bymyself. 31.3 at 5800 rpm. With the stupid bumpers down, whoops!
 
goldnrod24 said:
According to the 2014 brochure: Both 22' boats w/o motor

R Series with Express = 2384#

S Series with Express = 2456#

Hmmm.....
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OK, I dug deeper. According to the specs for each boat, here are the weights without the express tube retrofit. Since both of our boats are so equipped, the weight of the 3rd tube and shields will not affect the weight differential. Also, I had to use the 2375 RL specs since BM no longer builds the 2275RL boat (again, little differences as my boat has the extended rear platform and is nearly the same length as the 2375).

2375RL = 2700# (rounded)

21SLX   = 1900# (rounded)

So, is it possible that there really is as much as an 800# weight differential between these 2 boats? If so, that may explain what the best I can do is 28 mph. However, that does NOT explain that my pre- and post-retrofit speed numbers are identical.
 
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