do i need a jack plate?!

[muddyfishin]

hi, today i finally test drove my 16' mckee craft that has been a 2 year project, now that she is all done i hit the lake and everything was going great, engine fired up right away everytime, drove great and all that good stuff, so the time came to open her up on the lake and i could feel she was going to fly by 1/4 throttle,, that was until i planed out and looked back and alot of water was deflecting off the leg of the engine and filling the boat lol.. it is a long shaft motor and the prop sits kinda deep under the hull.. any help info and input appreciated

 

[Scott Danforth]

ok, so you have a 20" shaft motor on what size transom? 15" or 20" if you have a long shaft motor on a short shaft transom, your best bet is sell the motor and buy what you need.

 

[matt167]

agreed, sounds like it runs a 15" shaft.. short shaft outboards are getting uncommon but it's the right way to do it. Depending on what brand of motor you have, you might be able to swap lower units from a dead similar engine

 

[muddyfishin]

i measured the center of transom from top to bottom at 20", the motor i measured from the seam at the top of the lower unit to the base of the exhaust housing adapter plate is also about 20.. i do have a couple of inches to move the motor up with the transom bracket holes.. selling the motor is the last thing i want to do, if there is any other remedies, id like to try them first

 

[Scott Danforth]

your anti-ventilation plate should be about even with the bottom of the hull.

so stand back about 20 feet farther than you think, and take a picture of the bottom of your hull and the motor from the side with the anti-vent plate parallel to the bottom.

then take a straight-edge and hold it up to the bottom of the boat so we can see where it lands on the lower. that picture can be within a few feet.

 

[GA_Boater]

Move the motor higher. On my boat if I use the lowest position my splashwell gets a free wash job like yours. Two holes up made all the difference.

 

[muddyfishin]

okay im going to upload some pics in a minute, but off the bat i can say, that ihave about 2 1/4" of movement to play with on the transome plate to exisiting holes, the anit ventilation plate i assume is the higher edge just above the cavitation plate? im not too sure on that.. i have a hyrda foil but not installed yet, but that mounts to the cavitation plate correct? anyways the higher plate is exactly 4 inches below the bottom of hull pics coming

 

[muddyfishin]

[No message]

 

[GA_Boater]

Remeasure the transom. From the top of the transom where the motor clamps to the lowest part of the V. The anti-ventilation plate is the large one, not the small one above it.

I'm pretty sure you have a 15" transom and a 20" motor. Too deep in the water will the cause the splashing you're seeing. Mine works because it's a 20" motor on a 20" transom.

 

[muddyfishin]

from top of transom to the the lowest part of the v, (center bottom of hull) is 19 ",, so if the lower plate is to be same height as the bottom of hull, i need to come up 6 inches.. so i assuume jack plate is the way to go? or should i at least try to move up the transom bracket to the lowest hole first

 

[GA_Boater]

Then you have a 25" motor. Did the motor come with the boat? How is the transom?

 

[muddyfishin]

motor did not come with boat, i bought boat in 2018 and motor shortly after. tear down and rebuild on both, and in the past i had a feeling this would come to haunt me.. but that time is here and i need to find a solution.. i reallly dont wanna sell the motor so that is last last last option for me ive got alot of blood sweat and money in her. im thinking the cmc manual jack plate will give me enough adjustment.. oh and the transom is solidd..

 

[Texasmark]

Agree with the above.....your engine mid section is 5" too long for your transom engine mounting position to the bottom of the boat. If you don't want t sell the engine, get yourself an adjustable Jack Plate that attaches to the transom. Ensure that it has at least a 6" lifting range. When you install it, per the accompanied instructions, you will need to raise the engine mounting surface an additional 1" due to the setback.

Easiest way to check that is to use your straight edge again like you did in your second picture. The Anti-ventilation plate on the engine is the flat plate just above the prop. In your Jack Plate setup, set the AV plate 1" ABOVE the TOP of your straight edge for starters. Reason for the added inch is as you set the engine to the rear of the rear of the boat hull, the water level coming from under the boat has started to rise back to the surface level prior to the boat driving through the water and displacing it. Without compensation for that you will be doing some of what you are doing now.....running too much of the LU in the slip stream.

Trial and error on the height for the final tweak....what works best for you.

A manually adjustable plate isn't all that expensive and will work for your applications. Hydraulic are for high performance boats running over 50 mph. (opinion)

 

[ahicks]

If you aren't looking for perfection, maybe just wanting to see if what you have can be made "serviceable" (no shame there coming from this camp) raise the motor as high as you can and give it a try.

Another option might be to buy a junk 20" motor for next to nothing, and swap out the parts you need.

 

[Scott Danforth]

agreed..... your motor is 5" longer than it needs to be.