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Author Topic:   Mounting 25-inch-shaft Engines on 20-inch High Transom
peteinsf posted 07-07-2015 07:54 PM ET (US)   Profile for peteinsf   Send Email to peteinsf  
Here is my solution to mounting a pair of 25-inch-shaft engines on a 20-inch-high notched transom: two sets of CMC vertical adaptor plates. CMC-50012-5-INCH-verticle-extension-for-jack-plates-transoms-500.jpg

Prime and paint.

Add one custom cut and bent aluminum plate with counter sunk mounting and drilled to match upper drive bolts. A2D42DB0-7290-405F-BC8B-1C40F98B17E8.jpg E27D945E-5C0B-4B78-B9DF-0A3902BC9BFD.jpg 36DE51B5-9E14-45FC-B3E6-31EC19263521_1.jpg 954882E0-4EDD-4EC3-8650-FE27B6E355A9.jpg 0BCE6B74-BFA7-499F-9378-F72B6E3CF736.jpg

Caulk and add motors.

Pete (motors next)

Jeff posted 07-07-2015 10:25 PM ET (US)     Profile for Jeff  Send Email to Jeff     
Damn. That is stupid simple and perfect.
contender posted 07-07-2015 11:33 PM ET (US)     Profile for contender  Send Email to contender     
I hope you are not planning on using any type of hydraulic steering. These type of set backs (fixed) will not allow the motors to tilt up all the way. Your rams will hit the transom tilting all the way up.
peteinsf posted 07-08-2015 12:38 AM ET (US)     Profile for peteinsf  Send Email to peteinsf     
Hi Contender--I am not sure I understand the concern--not that I don't have a design problem. The top of the transom is 5-inch below the top of the filler plate.

The two steering rams are directly attached to the steering tubes across the front of each of the motors and are not attached to any part of the hull.

The CMC vertical bracket is less than 1/2-inch thick at the transom face and the filler plate is a sheet of plate aluminum.

I am not clear on what will hit the transom and where.


Jeff posted 07-08-2015 10:04 AM ET (US)     Profile for Jeff  Send Email to Jeff     
I agree with Pete, I don't see how a 5-inch riser plate is going to prevent tilt range and cause interference.

With set-back plates and hydraulic steering, it is common place to use side mount steering rams to overcome tilt interference. Scan_Pic0078_zps2f4272bc.jpg.html?sort=6&o=14 ETEC250Transom640x475.jpg

russellbailey posted 07-08-2015 03:46 PM ET (US)     Profile for russellbailey  Send Email to russellbailey     
That looks nice and clean and simpler than the hi-rise jackplates I had to use to get my setup to work.

contender posted 07-08-2015 09:13 PM ET (US)     Profile for contender  Send Email to contender     
Pete--what happened to me: I was re-doing my 17 (older 16'7") about two years ago, I purchased a 4-inch aluminum set back and attached it to the transom as you did. I purchased a new Teleflex Hydraulic Steering System for the Evinrude engine, with the ram center mounting to the steering arm on the engine. After the mount it looked great, I then used the tilt, the ram hit the transom and would not let me tilt the engine all the way up. I removed the setback and sold it to another person on this site, I advised him the same and he said he was not using the Hydraulic Steering. Maybe it will work for you good luck.
peteinsf posted 07-09-2015 09:02 AM ET (US)     Profile for peteinsf  Send Email to peteinsf     
Hi Contender,

Thanks for the clarification, it would be interesting to know what model of bracket you had. I think I will be OK in that the "CMC Vertical 5 inch adapter" plates move the motor back less than a ½ inch. In addition there is less to hit since the transom transitions into to a thin plate.


msl posted 07-09-2015 11:49 AM ET (US)     Profile for msl  Send Email to msl     

Contender is right on with his statement. I just had my transom raised 5 inches to go away from jack plates on my 25 outrage. I have new Baystar steering and it is very tight with motors trimmed up. I can get my port trimmed all the way up and my starboard motor is tight within 1/4". I am afraid to trim the starboard up 100%, my port is the slave on the steering. Being that it is only 1/2" set back you might be fine.

What motors will you be mounting on the transom?

Jeff posted 07-09-2015 03:15 PM ET (US)     Profile for Jeff  Send Email to Jeff     
What Pete is doing is only raising the transom 5". The extensions he has are not Jack Plates / Set Backs. They are keeping the motors mounted to and inline with the transom. They are just moving them up.....not up and back.

Just like this...

There should be no interference problems with steering components.

contender posted 07-10-2015 07:47 PM ET (US)     Profile for contender  Send Email to contender     
Jeff you are using the regular cable steering in your picture, This type of steering will not interfear with the transom, Using Hydralic steering the ram will hit on tilting the engine all the way.

Pete I think it was a CMC plate, but its been so long ago Im not 100%

peteinsf posted 07-11-2015 12:33 AM ET (US)     Profile for peteinsf  Send Email to peteinsf     
I finished the steering rams today and will post some pictures tomorrow.

Looks good on the clearance although I can not test the tilt since the battery cables to the outboard are not yet installed.

As a note, I switched from a single ram with a tie-bar to one for ram for each motor.

With that cool addition and going to counter rotation motors (had a pair of standard rotation units before) I am hoping she will steer like a Caddy vs the '49 Chevy pickup.

We will see...

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