Should I fabricate a jack plate for my boat?

[mr-asa]

I’ve got a ’56 Evinrude Fastwin on my boat, which has a 15" transom. The Fastwin is somewhere between a long shaft and a short shaft motor. I was wondering if I could raise up the motor a couple of inches and have a slightly more efficient setup for my boat, or would it not be worth the time?

[dan-in-tn]

Your Fastwin should either be a 15" or 20" motor? Did you mean your boat is somewhere between a short or long shaft transom? Otherwise I would be confused. IF you feel brave and the boat lends itself to it, a 2X6 or 8 can be put on the transom upright temporarily to mount the motor for a run. That way you could vary the depth of the engine and see how transom height effects performance. Otherwise building a plate could be a waste. It is true that moving the motor back will help, but on small boats that usually causes other problems (floating deep in the stern, waking over on deceleration, etc). All usual disclaimers apply about how to properly attach the board temporarily!

Dan in TN

[Mumbles]

The classic Johnnyrude shorties all hang a bit low in the water on a standard 15" transom. The A/V plate will be about three inches below the bottom of the hull. The OMC engineers might have designed them this way to allow for boats with keels which would introduce air into the prop.

[chinewalker]

You usually have an inch or so of play you can work with by shimming the motor up with a block of 1×2 or even a wooden yard stick cut into 10-inch chunks to act as "rev sticks". Make sure your clamp pads are still secure on the transom after each incremental height change…

[mr-asa]

quote t2stroke:

Your Fastwin should either be a 15" or 20" motor? Did you mean your boat is somewhere between a short or long shaft transom? Otherwise I would be confused. IF you feel brave and the boat lends itself to it, a 2X6 or 8 can be put on the transom upright temporarily to mount the motor for a run. That way you could vary the depth of the engine and see how transom height effects performance. Otherwise building a plate could be a waste. It is true that moving the motor back will help, but on small boats that usually causes other problems (floating deep in the stern, waking over on deceleration, etc). All usual disclaimers apply about how to properly attach the board temporarily!

Dan in TN

I think Mumbles explained it decently, but just to make sure everything is clear my Fastwin sits a little bit lower than any of my other motors except for my Gale 12D10 which has the same mid-length height.

Chinewalker, that’s a decent suggestion.

[johnyrude200]

An easy (and permanent) way to solve this, is to just buy some angle iron and place an appropriate 2×10/2×12 between them. Run 4-6 carriage bolts through the holes in the angle iron (you may have to drill out the angle iron) through your transom and that sucker will be strong as ever. If you’re just after 1-5" of flexible adjustment, those holes will interchange based on how you adjust your setup.

I had to do this last season on a pontoon boat that no matter what I did, either I had prop slippage, or water splashing back into the floor of the boat when at high throttle. Never really found a perfect solution, but after 10-12 different settings, I found something I could live with.

I’ve tried putting shims under the steering/mounting bracket, but with the older motors that usually don’t have a through-stern bolt pattern (particularly small ones), I’ve always gotten nervous that they might end up at the bottom of the lake. Doesn’t take much for a loose motor to take a swim….

[wiscoboater]

I’m assuming your speaking of your 12′ aluminum boat? You could fabricate a wooden motor plate ( I think your boat has one now) that bolts over your existing plate. That way you could remove or install it as needed. Make the new one a few inches taller and see how it runs. Use 3/4" ply laminated together with epoxy for a total of 1.5" and seal it well with a water proof finish. You would also have the added benefit of a bit more set back on the mount.

[mr-asa]

Wannabe, you nailed the exact plan I had if I do decide to do this.

Johnyrude, I always connect a clevis connected to a 1/4" steel cable to my motors to prevent them from taking a swim. I’ve seen it happen once to another member, once was enough for me.

[vintin]

Or bolt on a T.H. Marine Hi Jacker on that transom and enjoy the ability to make fine adjustments, switch motors, etc. Be sure when installing that you plan the spacing ahead for future motor mountings. Only drill that precious transom once! Rated to 150hp. Do it, you’ll be glad you did.

http://www.starmarinedepot.com/th-marin … gQodmrcCgQ

[mini-motors]

I once made an extension to accommodate a long shaft Honda, which was almost 10 inches longer than my transom. It worked just fine, but now that I want to use a normal sized motor, I’m left with some honkin’ holes to deal with. So if you do something, I’d advise thinking ahead on the chance that you might want to undo it someday.

What is the harm if it’s a couple inches low? The case with my Honda was a bit more than that, and it was a bit more HP than the boat called for, so I know why I did it.

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