Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: 70 HP Johnson Engine mounting process

Posted by Kayaken on 06/24/19 - 7:50 AM
#1

Let me preface with "I'm new to boats!". So I have found immense value in this forum and guidance.

I'm getting to the home stretch of a restoration of a 15' whaler. I'd like to re-install the motor that has been sitting in my garage on an engine stand for over 4 years while it waited for the hull to be prepared. i'm finally there! Yay!

So my main questions are about using the 4200 3M adhesive and process.

1. I noticed that there are 4 holes at the top of the engine bracket and a long slot at the bottom of the bracket. Which hole does the bolt go through on the top?

2. Do I need to put any 4200 on the back of the bracket where it meets the transom? For example, do I squeeze a line of adhesive around the back of the holes to create an o-ring seal?

3. Focusing on the top hole, I've read that I should coat the bolt when I slide it through the top bracket holes and as well as the washer on the inside. Once the bolt is through the transom and through the correct top hole, do I then coat the washer, slide that on, then screw on the nylon insert nut?

4. For the bottom slotted hole on the motor, do I follow the same steps as above with putting adhesive on the bolt and washer, slide it through the transom, then through the motor bracket, and tightening up the nylon insert nut? Where I'm stumped is how do I prevent water from getting into the transom since the motor bracket is a slot? Should I be filling up the slot with adhesive or creating a fillet with the adhesive where the bolt exits the transom hole?

Thanks in advance!
Ken

Posted by Phil T on 06/24/19 - 10:00 AM
#2

First thing is....

Put the tube of 3M 4200 down and slowly step away. There is no appropriate use of this adhesive on the boat unless you are fabricating something.

You should be using a marine sealant. Life Caulk's Boat Seal is one brand. If unsure, look on the packaging for the word adhesive. If it says that, put it back, that is not it.

Review this article: http://www.whalercentral.com/articles...cle_id=106

Review this drawing: http://www.whalercentral.com/articles...icle_id=82

Go ahead and measure the existing 4 holes on your transom and let us know what they are.

Once we know the above, we can tell you which holes to use or if you should redrill the lower 2 holes.

Also - What is the make/model and size of the prop on the engine. Look for a model # on the outside or inside of the hub.


Posted by Kayaken on 06/29/19 - 6:13 PM
#3

Measured the holes and the top two holes are 12 7/8” apart and the second lower set of holes are 6” lower and are 10 3/4” apart.

The model of the motor and is a Johnson model number J70PLEEE. Not sure how to determine the diameter of the motor. Is there a way to measure it?

I’ll attach a couple of pictures of the motor bracket holes in my next reply.

Thanks for the assistance.

Posted by Phil T on 06/29/19 - 6:40 PM
#4

K -

The holes are for using the "blind" holes. The modern BIA pattern uses the slots in the bracket for the lower holes. This allows the motor to be raised or lowered without having to re-drill.

If you use the blind holes (your bottom holes) your engine will be mounted at the lowest possible position.

The recommendation is to fill in the holes using plugs (not dowels) and epoxy and gelcoat and redrill the holes at the "green" location in the diagram.

Occasionally owners will avoid filling in the old holes by buying/installing a jackplate. The cost is ~$ 300 and adds stern weight which can exacerbate porpoising.


Posted by wlagarde on 07/02/19 - 2:07 PM
#5

Here is an example of the process on a 1976 Sport 15: http://www.whalercentral.com/userphot...lbum_id=64