CONTINUOUSWAVE

I acquired a Johnson 6-HP long shaft which I have stripped and rebuilt over the winter and plan to use as an auxiliary engine for my classic Montauk. I will be taking the 6-HP engine on and off [the MONTAUK] regularly. I want to minimise damage [to the hull and transom of the MONTAUK]. I may use adhesive treadmaster patches [to minimise damage to the hull]

Give suggestions on what to use to protect the hull.

Bend thin sheet metal to a U-shape that straddles the transom in the area where the auxiliary engine will mount.

jimh wrote:Bend thin sheet metal to a U-shape that straddles the transom in the area where the auxiliary engine will mount.

I think that is better than the adhesive patches tho OP mentioned but I would make it Stainless Steel or slightly thicker aluminum.

I would add a rubber material on the inside of the sheet metal U that Jim describes to protect the gelcoat.

To find an inexpensive source of thin and somewhat flexible sheet metal, visit a big box store and look in the kitchen accessories department for a baking sheet. Use that metal. Cut with a metal shear or tin-snips. Use a piece of wood as a metal forming brake. Visit a local vocational high school and ask the shop class teacher to help you bend the metal. Or just buy one of many transom protectors on the market.

The struggle here is protecting the gelcoat and allowing the outboard clamping bracket and screw clamps to produce enough "bite" to provide sufficient grip for a secure mounting.

My concern with introducing sheet metal is it tends to disperse the clamping force and some outboard clamping brackets have "teeth" that grip into the gelcoat. The sheet metal acts as a slip material since it is not bonded to the gelcoat. I would be more inclined to use the adhesive non-skid strips and apply those, making a secure bond between the adhesive and the gelcoat and these would also allow the outboard clamping bracket to have a "bite" into the non-skid material, while protecting the gelcoat.

Example of a outboard clamping bracket.


As a kid my small boat had a 1971 6hp Johnson and over time the rubber sheet we used to protect the transom became loose because the water acted like a lubricant and after a quick turn, the motor clamping bracket "walked" up the transom and scared me since I felt this movement through the tiller handle and I backed off the throttle. I was able to remove the lock on the transom screw clamps and adjust the motor back into place and ever since that time, I'm not a fan of material between the outboard clamping bracket and transom that is not bonded to the gelcoat and offers increased surface energy (friction).

D-

Like Phil said if you are worried about those grip ridges, include a high density rubber >1/8" (not foam) on the inside of your metal "U". This rubber will have enough friction between gel coat and sheet metal to keep it from sliding. I used this on my old Achilles for 20 years without the OB sliding.

If you will be using your auxiliary engine regularly, mount a permanent bracket--either fixed or adjustable and available from several vendors.

Or make your own.

Most brackets I have seen are mounted to the transom. The on-off and fastening and clamping is done to a block of replaceable wood or similar material.

The two-cylinder two-stroke Johnson 6-HP is a near indestructible workhorse with full gearshift F-N-R.

Being mounted to an auxiliary engine bracket also might make linking steering [to the main engine] easier.

[This URL points to a $110 bracket]
https://www.anchoring.com//products/sta ... gIKvvD_BwE

Thanks for everyone's input. I am very reluctant to drill holes to mount an auxiliary bracket. I think a rubber transom pad (shown below) looks like the best option.

What is the purpose of the U-shape notch in the rubber transom bracket shown above?

Mattwarner wrote:Thanks for everyone's input. I am very reluctant to drill holes to mount an auxiliary bracket. I think a rubber transom pad {shown below) looks like the best option.
transom.jpg

I agree as under-layment for a SS or ALuminum bend piece of sheet metal to disperse the force of the 2 motor mounting screws. This rubber protector will eventually get cut by the discs of the screws and the mounting back itself especially if you have some vibration (which you will have)
Again I recommend you bend (or have bend) a metal type "U" that fits over the transom saver pictured, therefor protecting the boat as well as the rubber from weather and cutting.

I was offered top money for the little Johnson 6-HP engine [whose method of being mounted on the transom so as to not damage the gel cost has been the focus of this entire discussion]. I decided to sell it.

My technical service fee is in the post.