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Engine Mounting on Bracket

3K views 18 replies 8 participants last post by  Lazerbrains 
#1 · (Edited)
Hi,

First, thanks to all who have responded to previous posts on fixing my O'Day Tempest. All the information and advice has been greatly appreciated.

I am currently considering how to strengthen the setup I have for mounting my Tohatsu 6hp 4 Stroke engine on the mounting bracket. Three pictures are attached.

The previous owner said that, although the Tempest has a well for the outboard engine, he used the bracket because the propeller and lower unit would get fouled-up if left in the water. I have also read that using the bracket avoids the fumes and grime and reduces drag by not having a propeller in the water under sail. The problems I've read about brackets is that they cause the boat to porpoise more in the chop and it is hard to operate the engine so far off the back of the boat (I'll need extensions for both the throttle and shift lever or a remote control).

Two changes I'd like to make about the current setup:

1) Replacing the board the engine attaches to. I don't know how old it is and I believe it would be best just to put on a solid new piece of wood. I have read suggestions to use a piece of Douglas Fir (2" thick, 1 1/2?), and I've also seen suggestions for two pieces of 3/4 inch plywood glued together. What's the best wood? And then for treatment, should I give it the usual West Epoxy layer?

2) Related to the board, the clamps sit a few inches above the top of the bracket. Would there be an advantage to use a slightly smaller piece of wood to bring the clamps closer to the bracket? I thought that would be a bit more stable.

3) On the inside of the boat, two strips of wood are used for the backing. Obviously, I need to replace the wood and the bolts, nuts and washers. My question is, would there be an advantage (or any problems) with using a single square piece of wood rather than the two strips? I thought a single piece would be stronger. There also seems to be a circular plastic pads between the wood and the hull. What is that?

Thanks for any responses to the above, and any other suggestions you may have on my bracket setup.

Alan
 
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#2 · (Edited)
I'd use plywood layers over a solid wood - epoxy sealed - for a new board if it's DIY, or the newer plastic/molded ones if new.

Lowering the board might make it awkward to tighten clamps.. Check that first.

There may be too much curvature in the transom for a single backing plate, but you can try that too. Consider going to a metal or perhaps G10 instead of wood.. It'll be forever then.

Agree to some extent about the issues of using an in-cockpit well, but your boat would be way prettier if you did ;)
 
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#3 ·
Ron,
Thank you for your response. I hope to have it completed in a few days although now I've been working on a stall at low idle problem on my engine. I do have thoughts about using the well as it's tough to operate off the back but main worry is about the fouling and the possibility of wrecking the engine. May gather more info. on that issue and perhaps try it.
Thanks again,
Alan
 
#5 ·
A couple of thoughts on the outboard well. On my boat the previous owner had glassed over the outboard well and added a bracket the same as yours (same motor too).

I found it difficult to downright dangerous to operate the outboard motor when coming into a slip, backing up, etc as I had to lean way over the transom. Furthermore, the engine cavitated easily in any type of chop or waves. I contemplated for awhile adding the control cables/lever setup which will cost you around $600. Decided against it and finally recut the hole in the well and use the boat as it was designed. Now backing up or entering the slip, grabbing a mooring, anchoring, etc, is easy as pie. Also, with the motor in the well, it works as a "stern thruster' making it even easier to backup in tight spots. I leave it in the well when sailing and have noticed no significant loss of speed, certainly not as much as a standard inboard prop would give you. I have been pulling it out of the well when done sailing as the Tohatsu isn't that heavy, but last month I bought some Petit antifouling paint in a spray can and sprayed the lower unit and plan on leaving it in all summer as an experiment to see how it does. I also changed the zinc at the same time. If you already have the outboard well, I suggest you try it first and see how you like it. Those motors certainly spoil the look of your boat. Motor is also harder to steal in the well. Just another opinion.
 
#6 ·
Lazerbrains,
Thanks for the suggestions about leaving the motor in the well as I am certainly considering it.

I had the same experience when I took the boat out in chop, trying to sit on top of the well and use the motor. Nearly went overboard. If I continue to use the bracket, I will definitely get a tiller extension and have also seen some DIY gear shifters online (a piece of PVC pipe attached to the shifter which is then guided by an attachment bolted to the motor cover with a hole in the attachment which guides the pipe. Seems to do the job.)

The Petit paint is a new idea. Did you have to tape over any areas of the lower unit to keep the paint off those areas (the intake valve or where the prop meets the rest of the engine) or just spray the whole lower unit that is below the waterline?

Thanks,
Alan
 
#7 ·
Hi Alan -

I took off the prop and sprayed it separately. I taped off the intake and the shaft, and sprayed the entire bottom. I then did a light spray inside the intake - just enough to give it a light coat. I have a buddy who suggested this - he has kept his motor in the well for 10 years this way with no problems - he just recoats with the Petit when it wears off, and pulls the motor out twice a year for servicing.
 
#8 · (Edited)
3) On the inside of the boat, two strips of wood are used for the backing. Obviously, I need to replace the wood and the bolts, nuts and washers. My question is, would there be an advantage (or any problems) with using a single square piece of wood rather than the two strips? I thought a single piece would be stronger. There also seems to be a circular plastic pads between the wood and the hull. What is that?

Thanks for any responses to the above, and any other suggestions you may have on my bracket setup.

Alan
My Tohatsu 6 hp 25 inch shaft is mounted on a 12 x 12 piece of 1/4 inch thick stainless steel, with multiple washers.

I have removed my ladder on the port side and put in anew mounting for a back up Torqeedo 1003. Even though the Tohatsu is 60 lb and the Torqeedo half that, I have still mounted it on a plate of 12 x 12 G-10, with two 1.25 by 8 inch steel plates on top of that. I have no wish having a $2000 motor falling off the back because it ripped out.

You might need to look to see if you have water leakage into your wood core between the fiberglass on the transom if its not solid Fiberglas.

I drilled it out wider than the bolt holes, taped it in the back and roto-routed into the core, and then put west epoxy into that area first. The I put a core plug of epoxy + filler(West system) into it again, and drilled through that. I used polyurethane adhesive on the G-10 backing and in a circle around the holes and used Picture hook screws to squeeze it tight. Once the back piece set. I champfered the holes on the outside. I Squeezed in 5200 adhesive sealant on the other side of the hole so that it was tight. I put the real SS bolts into it and I used Butyl tape around the edges of the hole and tightened the bolts. I then used a dull knife to edge the butyl tape.

The Torqeedo is only for the potential of having the Tohatsu die(had it happen with a Honda 5 HP 4 cycle) and don't wish to EVER have a repeat of that. Its not mounted except when needed---which I hope is never. While I have the potential for hobby horsing with a 60 lb engine back there, I do not sail on a lake, I am in near ocean, with a 3-4 knot tide and occasional large seas. When I need power, I NEED POWER.
 
#11 ·
Don't over think this, it's not rocket science!
Mine has had a heavier outboard on a bracket for over 40 years, just a couple pieces of what looks like oak 1x3 glassed in very similar to whats in one of your pics.
No cracks or any other issues on the transom. Last 10 years it's been a heavy 4 stroke 9.9 hanging back there. Boat gets sailed hard in some big waves with that 4 stroke tilted up so in theory the forces being applied to the transom are a multiple of the motor weight when dropping off 2 meter + waves.
The transom is one of the strongest parts of your boat!
Just make sure you seal up the through holes with some butyl tape, and do epoxy the holes if it is a cored transom to prevent water damage.
The motor board on mine has been replaced with what looks like a slab of 2" thick or so HDPE plastic.
Nice little boat you have but keep in mind what it's REALLY going to be used for, not exactly a heavy weather boat that is going to see hurricane type forces. There is strong and safe, then there is overkill to the point of absurdity!
 
#13 ·
Most "bracket mounts" were/are a poor compromise even when new. The reasons have been well stated by other posters.
The well installation worked great on a lot of smaller sailboats in the 70's, keeping the prop deep in the water, making steering a lot easier due to thrust against the rudder like an inboard powered boat, and allowing the use of a "short shaft" OB.

For best performance you just have to lift the motor out and store it under a cockpit seat. Cal 20's did this. Or just live with some drag under sail, much like having a fixed prop on a larger sail boat with an IB engine.

Added bonus feature is that such a cockpit design is hugely self-bailing.

Usually best to live with the compromise. Way safer than trying lean out over a transom.

Trivia: one historic feature that made this type of installation more palatable was that all of the small OB engines were two strokes. A 4 hp two stroke single or twin was really easy to lift out for more competitive sailing, back in the day. Modern four strokes keep getting lighter and the newest electric OB engines are nice too.

Loren
 
#14 ·
For best performance you just have to lift the motor out and store it under a cockpit seat. Cal 20's did this. Or just live with some drag under sail, much like having a fixed prop on a larger sail boat with an IB engine.

Added bonus feature is that such a cockpit design is hugely self-bailing.
Depends a lot where you sail. If you are on a quiet lake then its one thing. If you sail in a bay that has 3 knot tides, its something else altogether.
 
#18 ·
Hi Lazerbrains,
To your question, the outboard does not stick up higher than the hatch. The hatch will close on top of the motor but I keep it up so it's easy to reach the throttle and gear shift. Often, once I get out of harbor, I'll disconnect the gas line, flip the trottle back and close the hatch until it's time to restart the engine and drop the sails when I'm heading back to my mooring. I've been out 7 or so times now and it's working well and very easy to operate.
 
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