View Full Version : How DoI build a Jack Plate

Oz Dude
12-16-2008, 08:07 PM
So I was thinking that as I have a week off over Christmas and a mate of mine needs a jack plate for his new motor (3.0L Merc), I would see if we could fabricate one for him.

At the moment due to the worthless Aussie dollar, anything from the USA is worth big, big money, and as he only wants a manual plate, I'm thinking it won't be too hard when I have another mate that has a proper workshop.

The only plans I've been able to find so far are for a small motor. Does anyone know where I can find plans for a 500lb Merc jack plate??


12-18-2008, 04:46 AM
hey oz
good to see fellow aussies on this site
i was lookin into this myself,i wanted(still do) to build 1 for my 2.5
couldnt really find much except a heap on the lil' stuff.seen heaps of pics of
them,i would be thinkin that you'd just up the size of material you were to use
like 3/8 or 1/2 stuff out of ali angle with good stainless bolts (wouldnt use high tensile as they would be more inclined to just snap instead of bend if something were to go bad)
am interested in seeing wot pops up here

Oz Dude
12-18-2008, 04:55 AM
Hey Stiletto,

Hmmm, thought someone would have given some direction by now. I guess jack plates are cheap enough to buy in the USA verses here where they're big $$$.

We've got pictures of several different styles. Might still have a play over Xmas. See how we go.

Nice and warm where you are I bet! We having a week of it right now...


Warby Motorsport
12-18-2008, 06:09 PM

The Aussie dollar is bad news for getting stuff out of the States at the moment, it was good for a while nearly equal value, I have been getting small and Light stuff shipped out here, But a jacking plate would be a big Australian dollar Item,

I think one could be made, I would prefer Hi Tensile bolts, as I have had Stainless bolts stretch and fail at 100MPH plus on a rudder bracket, grade 8 high tensile you would not have an issue


Oz Dude
12-18-2008, 07:11 PM
Hi Dave - thanks for your input.

It must have been, ummm, "fun" having a rudder failure on the wrong side of 100mph... :eek:

HT Bolts it is!


Warby Motorsport
12-18-2008, 07:40 PM
Hi Oz,

at 120mph actually, in a blown hydroplane, the rudder needed more lay back on the leading edge, so a rudder design problem, the boat just spun out no major problem, BUT the Hi Tensile bolts held that time, the back of the boat didn't, I had lost the rudder in a test run previously, the bolts where stainless, they stretched like chewing gum,

I had always used Stainless bolts everywhere on boats, But after that I always put Hi tensile, Grade 8 bolts on rudders skegs etc etc


Oz Dude
12-18-2008, 08:00 PM
Hi Oz,

at 120mph actually, the boat just spun out no major problem,

Dave - that's a pretty big "brown pants" statement to make :thumbsup:

Seriously, as long as it was all good and not costly then well done!

Friends of mine used to own a Drag Hydro. At one meet, the river had weed running with the tide below the surface undetected. At 160mph and accelerating, the boat stopped responding to steering and slowly veered to the right. Ther driver got off the gas and, still at 90mph was standing up in the boat leaning down left on the steering with everything he had. The boat finally responded at about 60mph and he missed a wharf by about 10ft.

Not as dramatic as spinning at 120 but I can relate.

Oz :cheers:

Warby Motorsport
12-18-2008, 08:09 PM
Hi Oz,

I think any loss of steering is a bad feeling in all boats,

in a Drag hydro would be worse, as they don't like to turn at any speed!!


Oz Dude
12-18-2008, 09:02 PM
Yeah, I suppose at least your boat is designed to turn!

You in Sydney??


Warby Motorsport
12-18-2008, 09:12 PM
Yeah, I work here


Oz Dude
12-18-2008, 09:19 PM
Where's "here"?

I'm at Beecroft.


Warby Motorsport
12-18-2008, 11:36 PM
Sydney, Rockdale

Oz Dude
12-18-2008, 11:48 PM
Ok. I have friends that live at Kangaroo Point - not too far away...

Hope you have a great Christmas!

Warby Motorsport
12-19-2008, 01:31 AM
Thanks OZ,

All the best to you and your family over Christmas


12-25-2008, 06:18 PM
I am thinking of building a jack plate as well, they are too exspensive for me too and I live in the states!

I was thinking of getting 4 feet of aluminum angle, drilling holes is no pproblem but cutting the slits for adjustment might be a little tricky... any suggestions will be appreciated

Oz Dude
12-25-2008, 11:54 PM
bajaboy13 - if you look in the Metal Fabtication forum you'll find the thread where the guy made his own jack plate for a 50hp motor. It has good instructions re cutting etc. This may help you.

We've decided that we're going to rough one up out of steel first which is easy to weld and change as we need. Once we've got it right, we'll move to alloy and get the pieces milled for a professional finish.

Good luck with yours - post pics!!


12-26-2008, 09:00 AM
sweet I found the one on the GW and found this http://www.dillon-racing.com/jackplate/index.htm I probably wont be able to get at it till a while bc of school but I will keep posted!

Oz Dude
12-28-2008, 03:15 AM
That's the one - remember those plans are only for a small motor though!


12-28-2008, 09:04 AM
yeh needs to be a little beefed up for my tower of power!

02-02-2009, 11:37 AM
I have build mine myself.. Its adjustable to 4 diffrent heights..


02-10-2009, 04:02 PM
if you can find some 4"X4 or 6" angle in 1/2 inch alumunum and cut it into 2 pieces at about 18" long you can bolt the angles together to make a channel and a 2 piece plate, then to make it a one piece plate weld the 2 sections of channel together with a tye bar.. I can buy aluminum by the pound and have been thinking about building a 10" fixed plate for my fissin boat out of it... as it is 4"x6" angle 5/8 thick and long enough to make a 2 piece plate..

vista 88
04-16-2009, 07:47 PM
better just to buy one...so many cheap ones on the market now and you can mod it if needed

Thomas H
04-17-2009, 05:48 PM
the thread just below this one called Anyone build their own setback bracket, post #10 may give you some cool ideas.

11-21-2010, 09:14 PM
222293222292222291I went to Bob's Machine shop, near my home, here in Tampa, Fla. Steven,gave us a tour of the facility, and it is really high tech.All cnc machines,numerous tests on every component,the pumps are tested on 1000 lbs of weight.
We bought an Extreme Series, 4 in. setback, and had them install it. We have a 300 HP Suzuki, and here are a few photos of how it's made.

03-26-2011, 11:31 PM
I made mine out of 4x4 aluminum angle. It only holds up a 1500 inline . I wanted something with only 4 inches of set back so I just built it myself. Its manual and I have to use a car jack under the motor to adjust it. But it works for me.

Not sure if this pic shows it well or not.

03-27-2011, 07:03 AM
here is a link