Monday, February 24, 2014

A Little Too Secure.

Included with the purchase of my Leopard 38 catamaran was a dinghy with a motor.  The dinghy wasn't in the greatest shape (in fact one hole appears to have been "fixed" use the term loosely...with some sort of caulk like sealant that looks like bird poo) but it does hold air for at least a little while.  The motor, if it works, is a 2 stroke 15hp Yamaha...something definitely worth keeping if it runs or can be revived.  When I took possession of the boat, the motor was mounted on the dinghy and both were hoisted in the davits.  The weight imbalance was causing the davit bar to bend down on the motor side, so it was time to remove the motor from the dinghy.

You can see how the davit bends in this old picture.

The previous owner was apparently worried a great deal about someone stealing the dinghy motor and bought a fancy lock to lock it onto the dinghy in addition to his Master Cable Lock.  The Stazo lock is a big hollow square piece of stainless steel that fits over one of the clamping arms of the motor and prevents the clamp from being set free.  I rummaged around and found the key to the lock and gave it a try.  Of course, as is my usual luck, the lock would not budge.  I sprayed some penetrating oil into the lock...and a stream of rusty oil came out.  This does not look good.  Who would make a lock for an outboard motor where the lock cylinder would rust?

Stock photo - Mine was far more rusted.

The next several days I would spray some penetrating oil into the lock and try the key...and each time the lock would not budge. A fellow boater in the marina had a die grinder and some cut-off blades, so we decided that we would take the brute force approach and cut the lock off the dinghy.  It took two cutoff blades but we were finally able to remove the lock.  Underneath the lock I found a prime example of dissimilar metal corrosion as the stainless steel lock had corroded a hole through the aluminum motor mount on the transom of the dinghy.  I had wondered why that mounting plate had looked so corroded. It is true that aluminum doesn't rust (because rust is defined as iron oxide), but aluminum certainly does corrode. The entire motor mount was rather corroded and had warped to the point that, even with the lock off and the clamps backed off all the way, we were having a hard time removing the motor from the mount.  Cleaning out the (aluminum oxide) corrosion from behind the plate we were finally able to get enough clearance to remove the motor.

Trying to remove the motor from the corroded mount.

The motor is now resting comfortably on the pushpit railing mount and I have a new replace the corroded engine mounting plate on the dinghy.

Corrosion hole from the lock.

I was able to find a small, used piece of StarBoard (high density polyethylene plastic) at Sailors Exchange for a few dollars that I figure would work well as a replacement for the corroded mount.  I cut it to shape, drilled and countersunk the mounting screw holes, and viola, good as new...well...OK...not so pretty...but good enough for this dinghy.  No point throwing too much money at it when this should work for the remaining life of the dinghy.

Maybe not pretty, but a functional mount.

And below is part of the pile of aluminum oxide left behind after the replacement.  Too bad there isn't a sandpaper plant they would like to have it (your bit of trivia for today...some sandpaper uses aluminum oxide as the abrasive grit).

A lot of aluminum "rust" in the bottom of the dinghy when we were done.
Of course, in true boat project fashion, while working with the dinghy I found another problem.  The davit winch that spins nicely when free, squeaks under load and I also noticed the plastic stripper for the self-tailer is broken (after it tried jamming the davit line under the tab on the winch), so winch servicing is now added to "the list".  The dinghy and motor can now be separated and the davits look happier without the motors weight on them, so task completed.


  1. You definitely need to lock the motor to the dinghy. We use a Master Lock in the turning clamps and we have to spray the inside of the lock once a week with WD40 or something similar.

    S/V Kintala

    1. Oh, don't get me wrong, I do intend to lock them up. But I hope to find something a bit less complicated and prone to failure. The amount of corrosion was impressive...the pictures don't really do it justice.

      Do you have metal handles on the clamps? Our are plastic and I can't imagine just running a lock through them would be much of a deterrent.

  2. Don't you like dinghys and the related fun?
    Here's my approach

    1. If you can make one that will fold up like a transformer into a 5 pound briefcase, it would be perfect. ;-)

  3. Where did you grind--all the way around the stainless box?

    1. Hi Ted. It's been a while, but if memory serves, we cut near the opening you see at the top where the motor mount sticks out. That way there was less cutting to do...but you have to be careful about the mount and the screw handles.