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Author Topic:   Another twist on jackplates.....users please comment.
Bigshot posted 01-08-2002 03:33 PM ET (US)   Profile for Bigshot   Send Email to Bigshot  
I am going to be installing my 70hp Evinzuki 4 stroke on my Montauk this weekend. I have debated the jackplate idea and am a little cautious about hanging 342lbs 5-6" further aft.

Question is this...who has added one and what kind of performance "gains" did you get. For example: 70hp w/o bracket 1" above transom 17" prop=36.2mph. Same setup on 6" bracket=38.4mph, etc.

Any input from personal experiences?

lhg posted 01-08-2002 04:08 PM ET (US)     Profile for lhg    
I think I would do it, and I think you will like it. The weight offset will not be a problem, but be sure your cable steering can accomodate the offset. The reason I am hesitating, is that with 70HP, you're not quite at the speed where a performance/surfacing prop can be run, and where the flexibility of being able to "play with", and often change, engine running height makes sense . Generally, these props are for boats that run over 42, which would mean a 90 or 100HP engine. But there are some aftermarket props like "Stiletto" that you can use.

So your main benefit will be a slightly better ride, as the offset creates, in effect, a longer hull length and will lift the bow a little, getting the waves farther under the hull. Plus, increased running height should reduce lower unit drag, giving a few MPH gain. The ability to experiment, alone to me, makes it a worthwhile investment of $250.

Looking at the Cetacea page showing the two major styles of jack plates, I prefer the sleeker looking Springfield Marine (1/2" anodized alum)(Cabelas) or Rite Height (black painted aluminum) models shown, to the CMC model. The CMC is very wide looking on the transom because of it's concealed bolting design. Don't buy one of the old fashioned two piece models. You want the large center lift shaft.

noswah posted 01-08-2002 06:20 PM ET (US)     Profile for noswah  Send Email to noswah     

Big Shot, If you do a lot of fishing I think you'll want a Jack Plate as it allows you to fish in the shallow or skinny water. It also improves lots of other things.

To quote from CMC's brochure;

The power lift jack plate can improve the performance of virtually any type of outboard. The power lift gives you the ability to adjust your motor down for better hole shots or up for more top end speed. in order for your outboard to operate at it's full potenial and efficiency it should be adjusted at different speeds, water conditions, and loads in your boat. The Power lift or jack plate will put the motor back 5 1/2 inchs allowing the prop to run in cleaner water giving the prop a better bite and eliminating prop slippage.

Maybe Ihg knows something the rest of us don't, but this is the number one selling transom jack in the world, bar none. They have been making them since 1956.

Plus there are no hydraulic tanks or line in your boat it's all self contained in the unit. It is 40% more powerful and much more dependable than electro-mechanical transom jacks on the market.

lhg posted 01-08-2002 07:04 PM ET (US)     Profile for lhg    
I guess I missed the point that we are talking about HYDRAULIC jack plates here.
I was talking about the MANUAL ones.

The CMC units I'm sure are excellent, either hydraulically or manually operated. That is the buyers choice, and if I was buying a hydraulic one, I would buy CMC's. But it is also why the CMC MANUAL jack plate is a lot wider in size than it needs to be. It is the same "shell" that houses the hydraulic components of the hydraulic unit.

So that is why I like the MANUAL units by Springfield or Rite Hite. It is purely visual, but they were designed to be MANUAL. A prospective buyer of a jackplate should look at Cetacea page 41, and our Reference section on Brackets, and see which design they like the looks of best. I prefer the look of the smaller units. They are all of EQUAL quality, although the Springfield unit has a larger diameter center threaded shaft, and cost a little more to buy.

marc monreal posted 01-08-2002 10:45 PM ET (US)     Profile for marc monreal  Send Email to marc monreal     
Bigshot, I installed the 6" springfield Jackplate on my 78 Montauk and can't be happier. So far my top end has increased by about 21/2 to almost 4 mph depending on what prop I'm using. At this point I,m still experimenting with motor height and will post the resuts when I get more data. Like Igh, I went for the Sprinfield model because of the way it looks and is constructed. The one I have is brushed aluminum in color and looks really cool . As for the weight I wouldn't be to concerned. A friend of mine put a 90 zuki on his Montauk with the same Jack plate and is also very happy, however he enountered quite a bit of torque steer. Since adding hydraulic steering he hasn't had any further problems. Hope this helps. Regards, Marc
Flipper posted 01-08-2002 11:03 PM ET (US)     Profile for Flipper  Send Email to Flipper     
Bigshot: My 15 with 90 Merc w/o bracket 1" above transom, 26" prop : 50 m.p.h. average (with passenger).The same setup and weight with a 5 1/2" setback and 3 1/2" above transom: 55 m.p.h. average. The G.P.S. readings varied depending on where we were on the river each day ("bottom speed")!
I'm happy with this rig; one thing to look out for is, if you have hydraulic steering, make sure you have clearance between the cylinder and the jack plate when you tilt your motor all the way up.
Bigshot posted 01-09-2002 10:40 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Debating on it still but manual is probably they way I am going. I do not want a hydraulic because then I will be needing a low water pickup. Are you guys running low water pickups?
noswah posted 01-09-2002 11:17 AM ET (US)     Profile for noswah  Send Email to noswah     

Bigshot, If your only interested in top speed you can run a surface prop like a Cleaver. Most people DO NOT run a low water pickup on a hydraulic jack plate.

If you install a water pressure gauge you won't need the low water pickup. You should have a plug in the head of your engine to hook one to.

JBCornwell posted 01-09-2002 11:49 AM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Ahoy, Bigshot. As you know, I have a fixed jackplate mounting my Suzi 70 to my Montauk. It has a 4" setback.

Like you, I used it because I didn't want to go with blind bolting the engine to the transom.

I have not raised the engine (yet) and do not have a low water pickup. I do have a Sport 300 hydrafoil on it.

It comes on plane so smoothly I have to watch the spray to see the contact area reduce. It will reach 38mph (gps) @ 5800rpm with me alone and a full, 28 gallon tank, using a SS, 18" prop. If I trim it out a little more I am into porpoising.

With 3 aboard and a full load of gear it wont exceed 35 without porpoising, but will cruise at 30 (5000rpm) very smoothly.

I intend to experiment with a 1" or 2" raise and a 17" aluminum prop.

One important item we have not discussed before: My son's 2000 Montauk has a Merc 90 2 stroke, no setback. It is about 2-3mph faster (19"prop) but pounds much worse than mine, which planes with the bow about 4-6 degrees higher. The difference is dramatic in choppy water.

Hope all this helps you make a good decision.

Red sky at night. . .
JB :)

Whalerdan posted 01-09-2002 12:16 PM ET (US)     Profile for Whalerdan  Send Email to Whalerdan     
Your son's boat with a mercury 90 2 stroke is only 2-3 mph faster than your suzuki 70 four stroke? How can that be?
JBCornwell posted 01-09-2002 02:11 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
I don't really know, Whalerdan. With the 19" prop he tops at 38-39mph (GPS) with three aboard and a full tank. Mine, with identical load and a 18" prop starts to porpoise at 35-36 and seems to want to go faster, but is unable to remain stable. I call my top 35 with a full load and his 38 with a full load.

I rigged my boat, the Whaler dealer rigged his, but I don't find fault with his rigging.

Red sky at night. . .
JB :)

JBCornwell posted 01-09-2002 02:26 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Hmmm. Now that I think a bit more about it, WhalerDan, it could be because of the 4" setback and the smaller contact area of my boat at plane.

Additionally, we need to take "horsepower" with a bit of salt. Speed of a planing hull is a matter of how much torque is on the right prop, prop efficiency and contact area.

Too much credit is given to advertized "horsepower" ratings.

I don't make any claims about comparative horsepower ratings, but clearly the combination of factors my boat offers are almost as fast (on MUCH less fuel) as his.

BTW, he HATES it and has threatened to go to a Suzirude (I guess this year it will be a Johnnyuki).

Red sky at night. . .
JB :)

Bigshot posted 01-09-2002 02:48 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
You are right JB. My bud's 23 SeaCraft had 130 yamahas running 19"SS wheels. He ran 42-43 and cruised at about 30. He just installed 115 Zukis which added over 100lbs and is running aluminum props and only lost 1 mph on each end even though he dropped 30hp. The funny thing is he dropped 4-5GPH and at 1000rpm's burns less than 1GPH on both engines compared to over 2gph.
Whalerdan posted 01-09-2002 03:23 PM ET (US)     Profile for Whalerdan  Send Email to Whalerdan     
Maybe it has to do with the horsepower vs rpm chart. I wonder what rpm the 90 produces 90 horsepower, and what rpm the 70 produces 70?
One would think that the max horsepower would be at max operating rpm(ie approx 5500rpm).
dfmcintyre posted 01-09-2002 04:52 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
Bigshot -

I used the manual, but adjustable CNC unit on my Outrage with a 200 Yamaha. I debated on going the hydralic or the "semi" adjustable before settling on what I'd call the manual adjustable. It's the one with the jackscrew in it. I wanted to be able to ajust it, without having to use a chainfall, but didn't want to go with a hydralic on either.

I liked the choice. Painted it the hull color, which was great until the paint started to fail. Am planning on having it powder coated this spring, before going in the water.

CNC sent me a set of decals for free to reapply after the paint job.

Best - Don

lhg posted 01-09-2002 05:38 PM ET (US)     Profile for lhg    
JB- Clark Roberts has indicated that his 17' Whaler, with a jackplate, Merc 90 and high five prop, would turn 50MPH. Your son's boat must not be rigged for max speed at all.
He should set that Merc 90 back, lift it up a little, and get a Laser II prop for it. I think someone on this site is trying to sell a 20" pitch Laser. Also, a friend has Montauk with a 90hp inline 6 Merc on it, and it will do 47 without a jackplate, engine all the way down on the transom.

The ride improved immensely on my 18 Outrage when I installed the twin engines on the Springfield Marine 10" setback jackplates. I think it rides better than any other 18 Outrage I have been in. Consider this application for yours.

I would definitely believe that your 17' Whaler rides better than your son's because of the jack plate.

JBCornwell posted 01-09-2002 06:00 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
I agree, his boat is not rigged for max top speed. He had a 21" aluminum prop on it at one time, and it would do 42-43 but wouldn't pull his harem up fast enough on skis. That's why he put the 19" on it. It will now pull up to three nubiles at a time, though not at breakneck speeds.

My Montauk, "Sunshine III" is a fishing boat, soon to be joined by the infamous "Bent Boat" Outrage. She is rigged with fishing as her main mission. A 1" or 2" raise would give us access to skinnier water, and maybe increase her range a bit, too.

His boats main mission is play and entertainment of non-golfing clients, with fishing as a secondary use.

Red sky at night. . .
JB :)

Bigshot posted 01-10-2002 10:32 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
My mechanic says no plate...adds stress and will make it squat more. I am still debating, have until saturday to decide.
Wild Turkey posted 01-10-2002 11:24 AM ET (US)     Profile for Wild Turkey  Send Email to Wild Turkey     
Hey Bigshot.... Isn't the squat what you want? It reduces the contact area of the hull at plane. This reduction and allowing the prop to run in "cleaner" water is the performance boost. Also it think the squat might help the ride in a chop.
Are you worried about the extra weight of the 4-stroke compounded by the setback? i.e. hull stress
Bigshot posted 01-10-2002 01:26 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Yup! I am mainly worried about the porpoising factor. I have never used "doelfins" on Whalers and do not want to start now. What worries me is what JB said about the porpoising, wonder if that happens w/o plate.

Anybody ever run a Montauk w/o plate and then add one to the same engine? If so what do you think?

noswah posted 01-10-2002 06:05 PM ET (US)     Profile for noswah  Send Email to noswah     
Go to

and you'll learn more than you want to know about jack plates.

lhg posted 01-10-2002 06:52 PM ET (US)     Profile for lhg    
Porpoising is only related to trim angle. Trim in to normal operating range and it will not porpoise, unless the engine has inadequate tuck-in range.

Triming out, to increase bow lift and speed, is the least desireable way to accomplish this. By setting the engine back, and lifting it up a little, and using a bow lifting prop, you accomplish the same thing, but with the engine prop thrust more parallel to the water surface. If you look at the racing outboard rigs, none of them run trimmed out. Prop thrust is lost that way because of the force vector.

Bigshot, take a chance on the $250 investment. You can always remove it and sell it on this site. But you won't.

Bigshot posted 01-11-2002 10:56 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Ok! I will try and get to this place in Venice today. They have them $150 out the door. Polished alum, they are the ones on E-Bay. Do a search under Jack plates and you will see it for $134.95.
Bigshot posted 01-11-2002 04:05 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Got it during lunch. It is a Vance polished alum. 6" setback with I think 4 or 5" of lift. He also threw in an alum plate that goes inside the well connecting the bolts. Like the one with BW engraved on it in Cetacea. I then bought the big tubing that covers the cables etc from the hole to the engine(clean it up a bit). I also bought anodized Gaffrig red bezels for my Tach, speedo and hour meter which are also new. Putting in new rocker switches for the bilge pump, lights and acces. So it should be pretty nice(and neat)looking when I am done this weekend. Thanks for all the help and I will let you know how it works out.
lhg posted 01-11-2002 04:11 PM ET (US)     Profile for lhg    
Send Jimh some pictures so we can see it.
Flipper posted 01-11-2002 09:11 PM ET (US)     Profile for Flipper  Send Email to Flipper     
Welcome to the dark side! ;-)
bdb posted 01-13-2002 09:45 AM ET (US)     Profile for bdb  Send Email to bdb     

What is the name and location of the outfit in Venice you purchased that stuff from?


Bigshot posted 01-14-2002 10:48 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Actually in Osprey. Called Binder's Marine. Right on Tamiami trail(820 south?). I also bought a thick alum plate that connects the 2 sides of the plate theoretically making it a one piece plate. Makes it much stiffer, was worried the 2 sides might flex. No chance now. Looks awesome!

Got everything done except mounting controls. I thought I could use adapters on my universal cables(morse). NOPE! Gotta use OMC only so no boating yet. I mounted an hour meter where my old keyswitch was(red bezel too) and put in 2 Perko flush lights on the console sides for night illumination(Miami Vice effect). My full Mills cover is done and ready to be fitted(had it modified to fit around bow rail). Other than that she is done. Just needs a good bath and buff. Jimh do you want pics?

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