Mini Jacker or Transom Elevator?

[lester]

So I have been ravaging the posts on this subject and was just leaning towards building TD's transom elevator idea (thanks for the diagram), but found these two separate posts by TD that when quickly read, almost seem to contradict. Hopefully he can clear this up for me (I'm thinking he is refering to "his" jack plate in the second quote). Anyways does anyone have experience with both and have any advice? Thanks.

did you use my plan? picture of your boat and motor will help..if built right transom elevator is stronger than a mini jacker.

the jack plate is actually stronger that the elevator.

As an aside, do we have any engineers/physics gurus that can tell me how to calculate the amount of force created by offsetting the motor back 5" off the transom? I already understand that a long lever arm is created by this offset, but I want to know the force production increase by this offset.

 

[marquette]

Re: Mini Jacker or Transom Elevator?

i put a mini jacker on the back of a small fiberglass boat last summer. i hung a Johnson 28SPL on it. the mini jacker in itself is a very solid unit cast and machined from 1 piece of aluminim. however the plate and bolt pattern to fasten it to the hull is no larger than the bolt pattern of a 40hp. it doesn't spread the weight and flex out over much of the transom. i wasn't worried because i had just rebuilt the transom and knew it was sound. without knowing the condition of the transom i might have been worried about setting the motor back and like you say having the lever effect on the transom. TD's transom elevator design spreads the weight and torque out over more of the transom and doesn't set the motor back to give a lever effect. in my opinion his design would be less stressful on the boat. neither one is going to break under normal or even moderatly rough use. if you hit a sunken concrete pier doing 40mph the transom and lower unit are going to give before either the mini jacker or the transom elevator.

 

[tashasdaddy]

Re: Mini Jacker or Transom Elevator?

out of context it does sound contradictory. this is a manufactured transom elevator, that i would never put anything bigger than a 5 hp on, even though it is rated for a 40 hp. http://www.iboats.com/Transom_Elevators/dm/*******.473703934--**********.098980867--view_id.40157 it is only 14 inches wide, and does not distribute the load on the transom

for larger motors a true Jack plate is better if you look at my home made jack plate, it disperses the load, as a standard motor would mount on the transom. and puts the load on the whole height of the transom. look at this picture, you will see the yellow that is where the jackplate is mounted to the transon. with a metal backing plate on the inside.

 

[lester]

Re: Mini Jacker or Transom Elevator?

Thanks for all of help guys.

TD, just to get this right and clear the air:
in quote 1:

did you use my plan? picture of your boat and motor will help..if built right transom elevator is stronger than a mini jacker.

-TD was referring to his homemade transom elevator design compared to a TH Mini Jacker

in quote 2:

the jack plate is actually stronger that the elevator.

-TD was referring to the difference between his homemade jack plate and the transom elevator sold here on Iboats

TD, please correct me if I am wrong on this one. I am in no way trying to discredit you or your advice, just trying to get it all straight as the terms jack plate and elevator are generic and wasn't sure exactly what was being referenced.

 

[tashasdaddy]

Re: Mini Jacker or Transom Elevator?

you are correct in that context. Jack plates are usually used with BIG motors, made of heavier material. such as these. http://www.iboats.com/Jack_Plates_M...3703934--**********.482279908--view_id.217144

 

[Frank Acampora]

Re: Mini Jacker or Transom Elevator?

And the leverage of the jackplate comes from setting the engine back 5 or so inches off the transom. It is not increased leverage torquing the transom. If you consider the transom (or the last couple of feet of the hull bottom) of a boat sitting in the water as a fulcrum, the weight of the engine is further back. AHA! Thus: a Jackplate TENDS to give more bow lift--gets more hull out of the water---very desirable on a racing or high speed hull.