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Help !! - Jack plate or other method?

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knowles876 View Drop Down
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    Posted: 05/10/2017 at 2:28pm
I have a 26ft 2004 Odyssey 2502L with a Mercury 125.  I bought it last year and everything looks almost new.  It was well kept.

The issue I'm having is that I want to trim up the bow because the bow is pushing a lot of water.  I trim up just with a few bumps on the electric trim and the RPMs jump because the prop seems to be coming out of the water. (15pitch 13.75).  The motor is mounted on its lowest points.

Would a jack plate work to lower the motor, or use a setback, or some other means?  At the best I can set the trim, I get about 23MPH (GPS)

Any ideas?
Knowles876
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darrklim2 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darrklim2 Quote  Post ReplyReply Direct Link To This Post Posted: 05/10/2017 at 6:42pm
Do you have any pictures of the motor height right now in relation to the toons and transom?

from this angle

 

And this angle


Darren
Deer Creek, Minnesota, USA
78 Lund Mr. Pike
87 Sun Patio Sunliner DLX
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knowles876 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote knowles876 Quote  Post ReplyReply Direct Link To This Post Posted: 05/11/2017 at 3:05pm
It may take a couple of days but I will post some as soon as I can.  The boat is in a slip at a dock (in the water)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jakerichards1 Quote  Post ReplyReply Direct Link To This Post Posted: 05/14/2017 at 2:34pm
Hello. Having had much experience with a large 2 tube pontoon such as yours your speed is not far off from perfect world scenario. Jack plates are not designed to lower your motor, only raise it. You have 2 holes left on your motor mount; you could try lowering it and see if there is a difference. Then raise it all the way and see if it's any better.

I have a 28' with 23" round tubes and had a 90hp 2-smoke Johnson. 23 was best ever. And would ski at 21-22. Best prop was an 11x14 with motor all the way up and a bolt on anti cavitation fin. I forget the model but it was white and 300 in the model number. I did that to limit the occasional blow out(major slip) for no reason and I could turn greater angle at speed before blow out. Like when tubing.

The one thing I learned is that trim angle on a large boat has no effect on bow lift. The lever is too long. It does however majorly effect prop bite. Most pontoons run fully trimmed in/down.

It looks like your boat sits really deep in the water based on water marks on your tubes. That is either way loaded or full of water. That would really mess up speed and how the bow plows through water. If the back really is that low and everything is ok then lowering the motor will make it likely to take water into the cowl.

I would look for ways to add bouancy like a water glide or center tube with motor mount.

To make the front handle better, as is, maybe consider a better design deflector fin on the sides of the tube and or underskinning so the water flows better under the boat. Have you ever looked under the front at speed to see what the water is doing. Choppy days won't tell you much. Moderately calm water will let you observe what the water is doing and possible improvement opportunities.

My 28 full of people and dogs sits 1/2 submerged in the rear and about 1/4 bow. At speed the front bottom of tube is just at water surface.

This season is a new test for me because I just added a 27.5'eliptical center tube and a johnyrude 175. The tube is a brand new bennington 32"x26" oval with a 300hp motor mount. First test in the fall was wrong prop blow out at 26mph at 4000rpm but no loss of speed when turning. And I it banked!!! First observations was an even 5" higher in the water than before as measured on outer tubes. I mention this because the my goal of 30mph on an old boat is requiring double the power and 75% more bouancy.
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