Got my jack plate installed!

[Gfunk]

Tearing my boat apart for a paint job and took the opportunity to install the jackplate to fix my 25" motor on a 20" transom problem. Looks pretty high but when we checked it with a straight edge, the cavitation plate was even with the bottom of the boat.
Also, by the time we got it on there, I did the push on the motor test to see if the transom would move and of course, it did, just ever so slightly though, so it looks like we'll be doing the transom next winter. It will get converted to a 25" transom at that point. BTW, without the jackplate the transom was solid, but with all the added leverage, I was able to move it a bit. So I'd rather be safe than sorry.
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[tsubaki]

Being the setback you have, keep in mind it might need to be higher if the performance don't pan out.
Gotta run it and see!

[randlemanboater]

Nice work.

One inch up for every foot back so you should probably be 3//4 of an inch above the boat bottom with the cav plate.

[Destroyer]

Originally Posted by Gfunk

BTW, without the jackplate the transom was solid, but with all the added leverage, I was able to move it a bit. So I'd rather be safe than sorry.

Well, even the Empire State building moves in the wind. Doesn't mean it's not solid. Point is, you have added extra leverage which can put additional pressure on the transom. Even the most solid transom will flex under the right conditions. As Archemedes once said, "Give me a lever long enough, and a point to anchor it and I'll move the world". And of course what he meant was that as you increase the length of of a lever you also increase the force it can exert against whatever it's anchored to, providing the fulcrum point stays the same. So in your case, by increasing the length of the engine, you've also increased the amount of force your engine can exert against your transom. That doesn't mean that you have a bad transom that needs to be replaced.

[jasoncooperpcola]

I second what Destroyer said. Did you know there is a quarter inch gap between the actual transom core and the surface your motor bolts hit? its packed full of putty or it is supposed to be. If you are really worried about it add in some backing plates.

[Gfunk]

Thanks for the words of encouragement. I thought the same thing, probably just me being paranoid. It really was pretty solid before the jack plate. The bolt holes appear to be solid , no putty or anything. Given its age, this has been my number one worry though. Glad to have educated opinions weigh in on it.
Going to run it in the spring then monkey with the adjustment. Still have a 21" prop on, so I know I'm looking at a new one, I was just waiting till the plate was on to buy it. I was getting about 4800 rpms and about 38 mph before the plate, so pretty sure this will help break the 40 mph barrier pretty easy.

[RidgeRunner]

I wouldn't advise running the motor WOT for very long if it will only achieve 4800 rpm. That is a little low and potentially harmful to the internals on a 2-stroke. (pre-detonation)
I would try a 17p prop if going Mirage or maybe a 19p if smaller in diameter. Your MPH and MPG should increase.
My friend Lawrence installed a 30" Yamaha OX66 on a 25" transom height Parker Cuddy Cabin. That was 5 years ago and it had major movement in the form of transom flex from the very beginning. I think you will be OK for a season or two based on your description.

[Gfunk]

A buddy and I started early this morning and by 4:00 we had the bottom sanded and painted up to the water line and even had enough time to paint the trailer. I used devthane 379 in gloss black, great stuff, used it on several boats already with great results.
I asked a few of my trusty operators to lift the boat onto press stands, handy guys to have around and took the worry of me dropping off my hands.
Going to give the paint a few days to dry, and they'll come back and put it back on the trailer for me, then it's off to another friend of mine who will paint it inside and out. Going with fighting lady yellow from the rail down to the water line with some black stripes and off white on the inside. That is unless my wife gets her way and we go with light blue.

[Gfunk]

Not sure why.......
Think I figured it out.....

[RidgeRunner]

Nice job, keep it up.
Somewhere along the line I purchased some Fighting Lady Yellow. It never made it onto mine.
Oh I have no clue about the one at a time pics.