Jack plate on a 16' flat bottom boat?

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k5ride

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Joined
Feb 19, 2010
Messages
8
I have an 80' Fisher Marine 16' flat bottom with an 81' Johnson 25hp with a 15" lower unit. I was wondering if I could benefit at all from using a jack plate on this set up?
 
K

Kobie

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Jan 10, 2009
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Re: Jack plate on a 16' flat bottom boat?

How fast are you running? Your money is probably better spent upgrading the prop to a stainless then a jack plate.
 
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mpsyamaha

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Jun 8, 2007
Messages
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Re: Jack plate on a 16' flat bottom boat?

where is the ventilation plate in reference to the bottom of the hull at now? i had a flat bottom 16ft carolina skiff with a 30hp and it performed best with the motor set 1" above the bottom of the hull.
 
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k5ride

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Feb 19, 2010
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Re: Jack plate on a 16' flat bottom boat?

Kobie, not sure how fast I'm going. I plan to take the gps and find out. If i had to guess I would say 30 or so. I don't run a stainless in the river due to rocks. I'd rather break a prop than break something in the lower unit lol.

mpsyamaha, it was sitting about a inch below the hull, that's just how the motor always mounted. I used a strip of 1" wood to move it up and make it level with the bottom. I'm going to see how it works as soon as I can get to the river.
 
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bob johnson

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Feb 25, 2009
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Re: Jack plate on a 16' flat bottom boat?

k5ride said:
I have an 80' Fisher Marine 16' flat bottom with an 81' Johnson 25hp with a 15" lower unit. I was wondering if I could benefit at all from using a jack plate on this set up?
Click to expand...

what do you want to do, that is limiting what you can do now???

there are several reasons for a jackplate..

one of the reason i bought a jack plate was to be able to motor level under decent speed in very shallow water...

I dont need to plane out...just go faster than maybe 5 mph

with a regular motor you have to trim, which angles the motor..problem is as soon as you ask for just a little power it drives you back into the bottom!!

a jack plate can be araised keeping the same trim and when you give it that little more gas... the transom doesnt try to dive!!

bob
 
M

mpsyamaha

Chief Petty Officer
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Jun 8, 2007
Messages
400
Re: Jack plate on a 16' flat bottom boat?

my guess is that you will see better performance with you newly raised motor.

30mph is haulin *** in that little boat. just for reference, my previously mentioned skiff only did 27 on gps with a very light load. it cruised at about 20mph.
 
L

lckstckn2smknbrls

Lieutenant Junior Grade
Joined
Sep 18, 2008
Messages
1,114
Re: Jack plate on a 16' flat bottom boat?

I have a mini jacker on a 1436 jon with a 83 mariner 25hp short shaft motor.
The river I'm on is shallow and I wanted to get the motor as high as I could. With motor on the transom the ventilation plate was 2.5 inches below the hull. With the set back from the mini jacker I have the ventilation plate 2 inches above the bottom of the hull this is with a 1" wood spacer. No GPS speed yet but it's fast.
I got the mini jacker new on Ebay for $42.00 total.
 
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lckstckn2smknbrls

Lieutenant Junior Grade
Joined
Sep 18, 2008
Messages
1,114
Re: Jack plate on a 16' flat bottom boat?

I have the TH Marine "Mini Jacker" jack plate. It's a one piece cast aluminum and wood unit rated to 35hp. You can build a jack plate yourself from aluminum angle and wood. There are plans on the net.
 
K

k5ride

Cadet
Joined
Feb 19, 2010
Messages
8
Re: Jack plate on a 16' flat bottom boat?

Well did some testing today. I installed a new 9 1/4 x 11 prop and with the engine spaced up 1" it started to suck air as soon as I took off. Got rid of the spacer and it worked fine. Going by my GPS top speed up stream was 31 - 32 mph and down stream was 35mph.

I'd like to find a plate that has adjustable trim so I can get it dead on, which is hard to do using the stock pin adjustment.
 
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k5ride

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Feb 19, 2010
Messages
8
Re: Jack plate on a 16' flat bottom boat?

That's exactly what I was looking for! Thanks ddrieck!
 
D

ddaigle

Petty Officer 1st Class
Joined
Feb 9, 2004
Messages
332
Re: Jack plate on a 16' flat bottom boat?

I have been through this process. The problem is small outboard props have little cup to them so they have to be deep underwater to work. The best solution I found was get a lower pitch prop and then add cup to it which increases the bite and the pitch. About 6 in. of set back with a jackplate also helps quite a bit. With a heavily cupped prop and setback I was able to run higher than my water pickup would work so be careful. I have a solution for this problem also. Bobs machine sells a transom mounted water pickup for high performance boats. I modified a live well screen to fit it to keep weeds out. With my present set up I can jack the bottom of my prop higher than the bottom of my boat and run through weedy mud flats in about 4 inches of water. This is on my 18 footer with a 70hp and a 4 blade supercup prop.
 
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