Jack Plate for shallower running

[Aaron Lariscy]

I am curious if I can use a jack plate to get my outboard to run a little shallower, as it sits now the cavitation plate is 2 inches below the bottom of the boat. From what I have read for every 2 inches you move the motor back you can move it up one inch so if I were to make a jack plate that moved the motor back 2 inches I could move the motor up 3 inches correct. 2 for how much it is already low and another inch because I am two inches back. The whole reasoning is I run some pretty shallow creeks fishing and every inch counts. Boat is a 1232 and motor is a 7.5 mercury.

 

[Pappy]

Jack plates are being used sucessfully on small boats that need to run shallow. Never mind the theory of every two inches back you can move one inch up. That certainly wouldn't work on some of the Gil style brackets that are up to 36" back.....18" up would put the complete gearcase above water! Wish that old Wives' tale would go away. Anyway, you want to check and see where your water intakes are and make sure you do not bring them much above the bottom of the boat. In general you can start with your cavitation plate around 1.5 - 2" above the bottom of the boat measured with the cavitation plate parallel to the bottom, not trimmed in or out. That will get you in the ballpark. Bobs marine has a nice adjustable plate for not too much money if you want to go the easy route. Check to make sure you are pumping plenty of water all through your speed range and keep in mind that you may have to do some prop modifications the higher you go.

 

[Aaron Lariscy]

Ok I understand what you are saying on my merc the pickup is in the bottom of the cavatation plate just above the prop, now in the creek I won't hardly ever get above 1/4 throttle because the motor is plenty powerful so water pickup won't be an issue but in the river or lake in might be...

 

[Pappy]

You may still be good to go. On my vintage Johnson and Evinrudes the water comes in below the cav plate behind the propeller as well. Water is fed through the leading edge of a combination exhaust/water intake. My engines will run at this height with no issues. The slow overall speeds produced allow the water coming off the bottom of the boat to quickly ramp upward toward static waterline height which is an advantage for you.

 

[Aaron Lariscy]

10-4, I am going to start getting plans together for my jackplate. Yesterday I noticed a crack in my swivel bracket, I pushed on the prop while it was up and it broke and fell on the ground! Luckily a local guy had the parts to fix it and I got it fixed up this afternoon.

 

[BaitCaster]

I had my boat out this weekend for the first time since installing my mini-jacker. The cavitation plate now sits about an inch above the underside of the hull. I have no problems when running slow. At WOT the cav plate runs just below the water surface (it was pretty scary leaning over the transom trying to get a look!). I picked up about 1 - 2 mph at WOT with the jack plate. Not bad.

 

[jellio5]

I had my boat out this weekend for the first time since installing my mini-jacker. The cavitation plate now sits about an inch above the underside of the hull. I have no problems when running slow. At WOT the cav plate runs just below the water surface (it was pretty scary leaning over the transom trying to get a look!). I picked up about 1 - 2 mph at WOT with the jack plate. Not bad.

Where did you get that I want one.

 

[BaitCaster]

I had my boat out this weekend for the first time since installing my mini-jacker. The cavitation plate now sits about an inch above the underside of the hull. I have no problems when running slow. At WOT the cav plate runs just below the water surface (it was pretty scary leaning over the transom trying to get a look!). I picked up about 1 - 2 mph at WOT with the jack plate. Not bad.

Where did you get that I want one.

BassPro - https://www.basspro.com/MiniJacker-for-Clampon-Outboards/product/8782/-421340

 

[Pappy]

Baitcaster - Now you need to either shim the engine up a little or drill the next holes that are located 1" below the ones in use, raise it to the new holes and see what you get! Nice job! And.......although scarce, see if you can find an old 2-blade Michigan AJC417 for that old Evinrude 18. That prop is usually worth another 1-2mph. Let me know if you find two....I am currently borrowing one. With my '57 Johnson 18 I picked up an additional 1.2mph over a cupped production 3-blade aluminum and need an additional 2mph to hit the 30 mark in my 15.5' Gheenoe Classic. Haven't jacked this one up yet. Sold my plate with my 13' Gheenoe.

 

[Aaron Lariscy]

Hows this look for a home made jack plate, just mocking it up for now but it has the cav plate about an half inch above the bottom of the boat. One thing that bothers me is my transom seems kinda flimsy is there anyway I can brace it up some?

Sorry about the picture quality took them with my phone and the sun was at a bad spot. I really want to brace the transom up some ideas would be great. It might not be an issue right now but later down the road I don't what to have trouble.