How tight is tight?

Jay-

Very through post! Good thinking!

Here's an addition to consider:

When I bought my Yamaha 90 EFI aback in 2005, Gunther's Outboards in Sebastapol, Ca., offered to add an aluminum plate across the two top motor mount bolts that is about 3 x 12" x 3/8" thick. This spreads the load out nicely, possibly better than large washers. If I had it to do again, I'd add one at the bottom mounting set of bolts, too.

The plate had "Gunther' Outboards" cast into it in raised lettering, but for the $15 cost was cheaper than making my own, considering the various costs of collecting the material and time involved.

Two plates could be used, as one set of bolts are inside the top of the splash well, and the lower set down under it. Otherwise, one big plate would be nice.

Making your own plates out of aluminum would be a very easy job, since it, including most of it's alloys, are relatively soft, and easy to shape and machine.

Joe. :teeth :thup
 
I would be reluctant to use 5200 for setting the outboard bolts. It can be difficult to remove if necessary for service or movement if you need to move it up or down.

Aircraft self locking nuts are a broad category. Some folks use S S Nylox. I prefer a fine thread (1/2x 20 vs 1/2x13), and Cat 8 SS bolts/nuts, if you want a medium loctite that is appropriate, a second nut of SS, Nylox nuts would give additional security if you didn't want to go with Loctite. My personal preference is with a bolt with a bit more meat in the thread area than the Nylox as a primary nut.

Certainly 2" fender washers or an aluminum plate is advisable.
 
I would not use 5200 unless you plan on having the motor on that boat for the remainder of its life. witch in most cases wont be the case 4200 all the way, save yourself or the next owner the headache whenever the boat gets repowered.
 
Joe’s idea of using aluminum plat instead of washers is great, most steel suppliers of a scrap yard were you can obtain plate aluminum at a discount; I’d use 3/8th minimum. If you have a sidearm grinder it works great for cutting the plat, Home depot has wheels made for cutting aluminum and used for dressing up the edges.

Using the same lock nuts is probable fine; the 5200 will act as a thread locker. I like the quick set 5200 because it’s not as permanent as the slow cure, have not had problems with loosening previous applications were 5200 quick set was applies. Granted it takes a little more effort, I just sleep better at night knowing the motor is secure and has little chance of moving of the transom.
 
Not to be a spoilsport or anything, but, has anyone actually had an engine fall off or come perilously loose? Can't say I've ever seen it in my 26 yrs of outboard mechanics....We're not counting kickers here...Aloha, Steve.
 
Actually there are stories of motors falling off--you have to be a regular reader of "The Hull Truth" to find some of these. Certainly bolts loosening is relitatively common. Even more common--unfortunately--is the rot in transoms. There are a number of cases where the only culprit was the mounting bolt holes (I have first hand experience with that about 20 years ago with a Grady White).

As for transoms breaking, I also have first hand experience with that--happened to be a "space age plastic" on a 12 foot inflatable--which I ended up hand holding at 20 knots...until we got the dinghy to the boat, dropped my wife off on the first pass, and then she had a line to loop over the outboard on the second pass, so it didn't go in the water when I stopped it. (Exciting afternoon)

Breausaw makes a very interesting comment--that is that the Fast Cure (not quick set) 5200 is not as permeant the regular cure 5200. I am not so sure about the permanency (which may take into effect UV resistance etc), but there is a definite difference in the shear strength of failure with a SS fitting. (3M technical data bulletins). The mode of failure is in adhesion (no cohesion as it is with wood), and a 1" overlap with SS shows regular cure 5200 @ 352 PSI failure, the Fast cure 5200 at 197 PSI failure. Interesting Fast Cure 4200 fails at 138 PSI with SS, and only 38 PSI with Aluminum. Even more interesting is the newer 3M 4000 UV resistant adhesive/sealant, and it is very close to 5200--not as weak a bond as 4200!

Thank you for the information, and motivating me to examine the data sheets on the various adhesives. These numbers have implication in everything we bed on the boat--and leads me to believe that the 4000 is probably the best semi permeant deck fitting adhesive. Incidently gel coat adhesion is better than raw fiberglass and about the same as clean SS. Woods have far better adhesion to these products than do metals or fiberglass--almost double--and fail in cohesion, rather than adhesion.

In any case, it is best practice to route out the hull holes, and put in thickened epoxy to avoid any core problems.
 
jkidd":3j6lqcf5 said:
... is it possible that there are 2 layers. When I look in a hole it looks like balsa and then a layer of something else?
Click to expand...

I just happened upon this thread (searching for something else) and thought I'd comment, as I've just been over-drilling and filling holes in my transom (2002 22 Cruiser). Couple of observations:

1) The core in my transom seems to be balsa (thankfully dry and I aim to keep it that way!).

2) Not sure which tube/area you were drilling, but the upper part of the transom appears to have two layers - I was drilling from outside the boat and so it took me a minute to figure out why. I was over-drilling the holes for the upper swim-platform mounting fasteners and the order was outside fiberglass - balsa core - fiberglass - something - fiberglass. The "something" seemed to be a hard type of filler (e.g. something that started out as a paste and then set up rock hard). A bit of investigation showed that the "second layer" was the molded fiberglass motor-well, and the filler was between the inside fiberglass layer of the transom and the back of the motor-well molding. Following that logic, there were no "extra layers" in the transom below the motor-well molding.

Not sure if you were drilling at motor-well height, but if so, that may have been what you were seeing? (Of course that's not to say there may not be variations or other things in other parts of the transom either.)

Sunbeam :hot
 
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