jack plates, etc...

[lark2004]

I'm in the middle of rebuilding an old nobrand fibreglass boat, 15ft long, medium deadrise, that will be powered by an old 1968 evinrude 40hp with selectric shift. <br /><br />I am wondering how much benifit I would get from fitting the outboard onto some type of pod or jackplate. I see alot of threads mentioning setup, and can't seem to get any idea how much setback I should use. I know that the height of the engine is more or less trial and error, but the set back doesn't seem to be something that would be easy to adjust.<br />Any ideas?

 

[WillyBWright]

Re: jack plates, etc...

Jackplates are for high performance boats with big motors. I don't remember ever seeing one on anything with less than a V-6. It allows the gearcase to come farther out of the water which means less drag and more speed. For that you need to use a prop that's able to run partially out of the water. With your boat, the prop has to stay well under the water's surface. I'm afraid that you'd be wasting your time and money, and it would probably severely diminish performance on such a setup.

 

[lark2004]

Re: jack plates, etc...

cool, thanks for clearing that up, No-one seemed to mention much about what type of boat it suited. Thats one less thing I have to think about now

 

[WillyBWright]

Re: jack plates, etc...

One thing that might get you another bit of speed is trim tabs. You don't have to get big expensive ones, just the smallest manually adjustable ones available. They help push the bow down which lifts the back of the boat a bit on take-off, and you can trim the motor out another notch where you'd be porpoising without them. That gets you antoher 2-4kph. There are manually adjustable ones that would suit you best, plastic non-adjustable ones that would help too, but don't bother with the spring-loaded ones. A Whaletail might help with holeshot, but will slow you down, so don't bother with those either.

 

[lark2004]

Re: jack plates, etc...

yeah, I didn't like the idea of those foils and such that bolt onto the cavitation plate, but the trim tabs sound like a good idea, will have a look at shop for them. When you say manualy adjustable, How are they adjusted? is it like a hydraulic control that you can use from the helm?

 

[walleyehed]

Re: jack plates, etc...

Jackplates are for high performance boats with big motors. I don't remember ever seeing one on anything with less than a V-6.

Ouch!!!<br />Don't tell Dhadley that...he'll think the gained performance we've seen on the smaller rigs, was all in our heads.....

 

[Dhadley]

Re: jack plates, etc...

Bummer! <br /><br />Cant believe we've been doing it wrong all these years. Heck, we used a fin and a jackplate on the Allison with both the V4's. <br /><br />Does this mean I have to send back all the trophies? Can we at least keep the speed records?<br /><br />Kenny -- good thing you changed to a V6.

 

[WillyBWright]

Re: jack plates, etc...

I never said there were no exceptions, I just said I haven't seen any. Got any pictures? And I'll bet those foils were clear of the water once the boat planed, right? I didn't know Allison made a 15' family runabout. <br /><br />The manually adjustable tabs I mentioned are adjusted by a screw on the tab. Hydraulic tabs are awfully expensive and they'd be way too big for that boat. I have a pair made by Tempo-Curtis. I haven't seen them in any catalogs for awhile. I have seen something called Smart Tabs that look like a good possibility.

 

[lark2004]

Re: jack plates, etc...

ok, will look into it, thanks for the help

 

[lark2004]

Re: jack plates, etc...

How expensive are the manually adjustable tabs in the States? they seem to be about $800.00 over here in Australia. I might look into making a set if I have to, other wise I will just live with the boat the way it is.

 

[BillP]

Re: jack plates, etc...

Manually adjustable tabs are EASY to make. I made them for an 18' flat bottom ski boat with a 110 Merc and used SS continuous hinge, 1/4" thick 2024 aluminum sheet and bronze turnbuckles. Cheaper materials will work too.

 

[phatmanmike]

Re: jack plates, etc...

i simply dont see how a jackplate could EVER be a BAD idea.... ive seen em on boats with 2 and 3 cylinders, and they work excellent.<br /><br />but then again, what di I know

 

[phatmanmike]

Re: jack plates, etc...

the manually adjustable tabs are around 100 dollars up to about 200 dollars here in the states. have a buddy here in the state mail you a set and you could save a lot of cheese

 

[WillyBWright]

Re: jack plates, etc...

You have to keep his boat and motor in mind. It's an old 15' fiberglass runabout with an old 40Hp Evinrude. The prop style and water pump intake won't tolerate much raising of the motor on the transom without sucking air. It'll also add weight to the back end, magnify the weight of the motor by moving it out beyond the transom, and you really don't want to do either. On many newer packages, jackplates do a marvelous job. On lark2004's, it would be a bad choice in just about every category I can think of. There is something called a Mini-Jackplate that would be the only one I could endorse. It doesn't weigh much and it won't move the motor very far back. It's also the cheapest one, but I doubt it would give any better hole shot or speed than just planting the motor on the transom.<br /><br />The expensive tabs are probably hydraulic. I wouldn't spend that kind of money on that boat. I definately like the home-made option.

 

[tee-boy]

Re: jack plates, etc...

Performance is a general word and does not only apply to speed and acceleration. Jack plates are often used on the Southern coast to allow for running in shallow water. The reduced drag thing is just a positive externality from our view point.

 

[lark2004]

Re: jack plates, etc...

Ok thanks for the input guys, Gunna make my own tabs.

 

[kfa4303]

Re: jack plates, etc...

I use a jackplate/transom riser on my '66 20 hp Johnson and it works great. You'll also see lots of folks in my neck of the woods use them on small motors as low as 5 hp. We use them to get into super skinny water, but they also help reduce/eliminate porpoising and other performance issues. Check out microskiffs.com and/or Bob's machine shop.om for examples.