Jack plate on a 14' Jon Boat

[doodlebug]

Hi folks, new person here with a question. I've got an open Jon Boat with a short transom that I want to run a 20 horse Merc with a long shaft. The person I bought the boat from had rigged up a piece of wood to elevate the motor. It was real flimsy and dangerous I thought. I've been looking at a mini jack plate to install and mount the motor on that would raise the motor 3 inches. By my calculations that would put the cavitation plate about an inch above the bottom of the boat. Do you folks think that would be ok? Appreciate your recommendations and any ideas you might want to provide. Thanks

 

[Blake]

How much is the setback on the jack plate?

 

[doodlebug]

It has a 4 inch set back.

 

[lckstckn2smknbrls]

I'm using a mini-jacker with a short shaft 1983 25 hp Mariner on a 1971 Wards Sea King 1436 jon with a 16" transom. Even though it's a short shaft motor it's longer than 16". With the 4" set back I have the anti-ventilation plate about 2" above the bottom of the hull.

 

[Blake]

The rule of thumb is that you can raise the vent plate 1" above the bottom of the hull for every 2" of setback. So you should be fine. But it all depends on water pressure and or if the motor starts cavitating due to being too high.

 

[doodlebug]

I think I'm going to give the mini-jacker a try. I've read some reviews and most people seem to like them a lot. First thing I've got to do though is try to patch all of those blasted holes in the transom. It must have 20 screw or bolt holes in it.

 

[riverbud55]

Did some research when I built my jack plate and found that people had problems with more/excessive bow rise on small tiller boats when they added a jack plate with much of any setback,,, moving the motor back moves it further from the center of the boat putting more load on the rear, then add that your body has to reach further back to reach the tiller just adds more weight to the rear, also depending on how long the handle is on your tiller and your boats seat location may make a little harder to reach,,,,,, may be bs but made sense at the time and still does to a point, ,,, any thoughts?????
here is what I did on my G3 with a 15'' transom with a long shaft e tec

 

[turbotodd]

Did some research when I built my jack plate and found that people had problems with more/excessive bow rise on small tiller boats when they added a jack plate with much of any setback,,, moving the motor back moves it further from the center of the boat putting more load on the rear, then add that your body has to reach further back to reach the tiller just adds more weight to the rear, also depending on how long the handle is on your tiller and your boats seat location may make a little harder to reach,,,,,, may be bs but made sense at the time and still does to a point, ,,, any thoughts?????
here is what I did on my G3 with a 15'' transom with a long shaft e tec

CMC PT35 or PT130 will help drastically with this. It really serves several purposes. One, and it's intended purpose, is to add tilt and trim. The secondary effect is that it moves the motor back 5.5". Normally with the setback, yes, you'll see some more bow rise. But the ability to trim solves this; as you can move the trim pin on your motor to it's lowest setting (some guys remove it totally) and then that gives you more "tuck" (negative trim), which helps get the boat on plane quickly. Once it's planed, trim it out until speed increase stops or porpoising starts. When trimming out with the CMC (or panther, etc), as the CMC is lifting, it's also moving the motor upward a little, which kind of gives it a jack plate effect. It is not at all uncommon, with a typical duck boat around here (1542-1548-1553 with 25hp) to gain between 3 and 8 mph with the CMC alone as long as it's set up correctly.

I have run a manual jack plate before on my other boat; and that is one of the things I too noticed. Lot more bow rise but I don't have the ability to trim while under way. If you have trim, that problem disappears for the most part.

My next boat mod will be trim...whether it be a CMC or Panter or whatever brand, or it be a new motor. It will have trim/tilt eventually. I'm getting too old and lazy to manually tilt that big heavy 4 stroke motor. I can kick it in reverse with the tilt unlocked and that works but only if I have the space. Sometimes theres areas where I can't do that, like, say, a stump or log is right behind the motor which would hit while the boat is backing up slightly.

I saw one, don't remember the brand, but it had tilt/trim AND a jackplate built together, made for smaller motors. That peaked my interest until I saw the price tag :O

 

[riverbud55]

Did some research when I built my jack plate and found that people had problems with more/excessive bow rise on small tiller boats when they added a jack plate with much of any setback,,, moving the motor back moves it further from the center of the boat putting more load on the rear, then add that your body has to reach further back to reach the tiller just adds more weight to the rear, also depending on how long the handle is on your tiller and your boats seat location may make a little harder to reach,,,,,, may be bs but made sense at the time and still does to a point, ,,, any thoughts?????
here is what I did on my G3 with a 15'' transom with a long shaft e tec

CMC PT35 or PT130 will help drastically with this. It really serves several purposes. One, and it's intended purpose, is to add tilt and trim. The secondary effect is that it moves the motor back 5.5". Normally with the setback, yes, you'll see some more bow rise. But the ability to trim solves this; as you can move the trim pin on your motor to it's lowest setting (some guys remove it totally) and then that gives you more "tuck" (negative trim), which helps get the boat on plane quickly. Once it's planed, trim it out until speed increase stops or porpoising starts. When trimming out with the CMC (or panther, etc), as the CMC is lifting, it's also moving the motor upward a little, which kind of gives it a jack plate effect. It is not at all uncommon, with a typical duck boat around here (1542-1548-1553 with 25hp) to gain between 3 and 8 mph with the CMC alone as long as it's set up correctly.

I have run a manual jack plate before on my other boat; and that is one of the things I too noticed. Lot more bow rise but I don't have the ability to trim while under way. If you have trim, that problem disappears for the most part.

My next boat mod will be trim...whether it be a CMC or Panter or whatever brand, or it be a new motor. It will have trim/tilt eventually. I'm getting too old and lazy to manually tilt that big heavy 4 stroke motor. I can kick it in reverse with the tilt unlocked and that works but only if I have the space. Sometimes theres areas where I can't do that, like, say, a stump or log is right behind the motor which would hit while the boat is backing up slightly.

I saw one, don't remember the brand, but it had tilt/trim AND a jackplate built together, made for smaller motors. That peaked my interest until I saw the price tag :O

ya here you on no power tilt/trim, had 1 boat without and it will be the last,, the little etec has a true power trim , for the most part the 25 hp n less have power tilt and not trim, one of the biggest reasons got the etec,,,, ???? so is the gain in mph gained by the set back or being able to trim???? understand triming out and unsticking the boat is going to give speed,,,, trim out my tin bass boat with a 75 hp bet the thing picks up 10 mph+,,,, mite just try a 4 or 5 inch tube or C channel for a spacer and then raise the engine a few inches,,,, fish n a marsh that 95 % of the water is less then 2' could be a little help also

 

[Flatbottomhick]

This is what i did on my 15' G3, 5" of lift and works geat. Cost me 40$ with the stainless hardware.Works great. I have added some more holes for a little more adjusting, but at 5" it is perfect.

 

[onthewater102]

I've been trying to build my own combination jack plate & tilt trim but the hydraulics involved push the cost to the point that it's really not saving much money over that already available design. The only difference is I'd be planning on using 3/8" aluminum angle so it could handle a 60hp whereas the out of the box combo unit I think is only rated to 40 or 50 hp.

 

[jy951]

Seems like out would be much easier to just sell your motor and buy a short shaft.

I would think adding the mini jack would cause extra stress inn your transom.

 

[lovedr79]

you should be fine.

 

[Flatbottomhick]

I used 3/8 angle for my 20hp jack plate. Very straight forward.

 

[onthewater102]

all the factory jackplates use 1/4" for up to 40~50hp so 3/8" is more than enough

 

[Stumpalump]

I've been trying to build my own combination jack plate & tilt trim but the hydraulics involved push the cost to the point that it's really not saving much money over that already available design. The only difference is I'd be planning on using 3/8" aluminum angle so it could handle a 60hp whereas the out of the box combo unit I think is only rated to 40 or 50 hp.

Here is the Jack plate and trim combo you and Turbotodd were referring too.
https://www.bobsmachine.com/Combo-Tilt-Jack-Clamp-on-or-BIA-50HP-100-106016.htm
It's rated for a 50 four stroke but a 60 two stroke weighs less. I called and asked and of course they stick to their recomended 50 hp. I will end up with one and have been searching the dealers ect for a sale or a deal to justify the cost. They must sell them overseas to be getting $1750 for them. The only deal I found was they offered a bandanna and filet knife with every order on Black Friday. My trim is getting worse and I need just do it but that's more than I spent on the whole boat! Manual jack plates are fine for top end only but my boat is used for so much more than just fishing or going fast. I want to raise it way up in the rocky no wake shallow rivers above the AZ lakes. If anybody finds this a little cheaper please please let me know. I'll buy it, try it and report back.

 

[lovedr79]

$1700? i am in the wrong business

 

[onthewater102]

The linear guide rail and carriers are ~$250, another $250 for the hydraulic valve, $150 ea ($300 total) for the hydraulic cylinders, $400 for the pump & reservoir plus the aluminum, hardware, tooling & misc other parts (switches, hosing etc.)

try & build it and you're looking at being in the neighborhood of $1500 easily - a turnkey solution is really appealing.

If I recall correctly the Bob's design uses 1/4" aluminum for the mounting brackets & plate which is likely where the HP restriction comes from. That's not to say it wouldn't work with a 60HP motor - but I don't know that I'd be comfortable with it if the engineers that designed it are saying not to use it in that application. Hitting some rough water and lose your engine @ full throttle sounds awfully dangerous to me.

 

[Hanr3]

WOW!!!! $1700 is more than twice what it costs to buy a tilt and trim kit.
https://www.basspro.com/CMC-Power-Tilt-and-Trim/product/1137/

Buy the tilt and trim kit, save yourself some money, it performs like a jack plate but has the added features of tilt and trim. That jack plate will only raise and lower the motor vertically. Won't do a dang thing for tilt or trim. My boat came with a jack plate, told the previous owner he could keep it. Saved me $500. One of these days I'll be buying that CNC tilt and trim unit. Oh, by the way, it's rated for up to 130hp motor too...

 

[onthewater102]

Add the price of your tilt & trim to a hydraulic jack plate and compare apples to apples - sure a civic is cheaper than a ferrari - but what is the point in the comparison?

Running shallow I used the jack plate on my fiberglass boat just about every time I took the boat out. I'd definitely want to have both if given the option. Having them operate off one hydraulic pump saves weight in a light boat - and isn't that the point to these little tinny's anyway?