Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: 1984 Outrage 18 Center of Buoyancy

Posted by BruceT on 10/30/15 - 9:33 PM
#1

I am planning to install a jack plate on my Outrage, but not sure which make and what set back to use. I see that I can go from 4" up to 12". Since this will move the center of buoyancy toward the stern, I also plan to move the two batteries into the console as an offset. I don't want to do this using Kentucky windage so I am looking for some reference to the center of buoyancy for the boat, from which to calculate. Where can I find that information?

Also what experience has anyone had when installing a jack plate, right now I am thinking of the SeaStar with a 4" set back (minimum rearward movement). The motor is a 150 HP HPDI, two stroke Yamaha, which weighs in at 500#.
Thx
Bruce

Posted by JRP on 10/31/15 - 8:33 AM
#2

My 19 Outrage II (same hull as your Outrage 18, but different interior configuration) is fitted with a 6" set-back bracket with a Yamaha 150 2-stroke (430 lbs plus about 25 lbs for oil tank reservoir in stern locker). It was rigged like this when I purchased it, so I can't give you any insight into "before and after."

It seems to work well enough as configured. The Detwiler bracket allows the engine height to be more finely adjusted, since you aren't limited to mounting-hole increments (it is a sliding track system.) Mine seems to be raised up pretty darn high but I have never fiddled with it.

My impression is that the boat squats a fair bit with the engine hanging so far aft, unsupported by the buoyancy of the hull. So my suggstions would be to go with a 4" set-back bracket, to limit stern squat.

If you find line drawings that show the fore-and-aft center of buoyancy, please let us know.

Posted by Phil T on 10/31/15 - 11:37 AM
#3

For those, like me, that don't know, here is the definition of "Kentucky Windage"

Kentucky Windage is the practice of applying a horizontal adjustment of the point of aim for wind (windage) without the use of any physical or mechanical adjustments on the weapon.


cf: http://www.urbandictionary.com/define...%20Windage

While I live in Kentucky, I moved her 3 years ago from Maine.

Posted by BruceT on 10/31/15 - 1:56 PM
#4

Thx JRP, I will post any data I obtain. If I use center of gravity calculations, i.e., weigh x moment and divide total moments by total weighs I get a movement forward of appropriately 1 foot, with the 4" see back. I agree with you that the stern squats on the Outrage a little already, so I can see where yours would a little more so with the 6" set back

Posted by BruceT on 10/31/15 - 2:06 PM
#5

Phil,
Thanks for the reference, I used the term in the more general sense of what I think is the more common definition, namely a guess without any calculations. The term also has its roots in the Kentucky long riflemen, which ironically came from Pennsylvania.

Posted by Marko888 on 10/31/15 - 5:09 PM
#6

When I replaced my 1985 Johnson 150 with Suzuki DF140a, I moved my single G27 battery to the console. The engine weights are very close. I could feel the CG was a bit further forward than it had been prior to the battery move.

Ive also run my 18 with the old 150 and 100# kicker on the transom. Adding the kicker greatly diminished the boats handling, which is why I chose a light engine (407#) and battery move. I think my boat would handle the kicker just fine now.

With a 500# engine, I would also suggest less will be more, and would choose the 4" setback, and batteries moved to the console.

Posted by tedious on 11/01/15 - 3:24 AM
#7

Bruce, can you clarify why you're looking to install a jackplate? That's a very heavy motor, and if you are just looking to get into shallower water, I would recommend keeping the motor as close to boat as possible.

Also, I think Kentucky windage is the only way to go here - at this point in their lives, all Outrage 18s have different weight distribution so one person's experience won't match another's.

Tim

Posted by gchuba on 11/01/15 - 6:45 AM
#8

I have a 22' 1979 Revenge that I operated with a 6" mechanical jack plate. I found my trim tabs (which came with the boat) to really aid with my ride. I highly recommend reading articles from Continuous Wave: "Standard Transoms and Brackets" and "Engine Setback Brackets" (the articles have highlighted blue print that sends you to accompanying information). I have since installed a 10" Bobs Machine Hydraulic Jack Plate which I have yet to operate. The 10" setback freed up my entire deck

I was able to re use my cable steering with the 6" offset . I would have kept the arrangement except I have a low cut transom which, with the motor now completely clear, I could install a removable splash board. You will need to tweak the weight distribution. I did send a jack plate back to the manufacturer. Even though it was "rated" correctly the the quality of materials used did not stack up against the Bob's or Springfield. I bead blasted the Springfield plate and had it type III anodized if you are interested.

To help balance the offset my two batteries are now forward, my fishing lead is forward, and my anchor now has chain to go with the line (stored at the bow of the boat).

My installations were to free up deck space. Raising the motor manually for shallow excursions not feasible and think hydraulic. Really think about your reasons for the installation. I found out that my installation was a "...far cry from mounting it and boating into the sunset....".

Garris

Phil....I always thought the term was "...Kentucky Vindage..." in reference to back woods hootch

Edited by gchuba on 11/01/15 - 6:58 AM