dbulich:
You need to be a little careful adding (gas) engine mounts to the fishing rod holders on either the AI/TI. Not really the intent of the design, as they are only supported on the deck and free to do what they want down below (no support from below). Of course it can be done and many of us have done it (some more extreme than others LOL).
Basically the engine mounts are very simple and can be built in a couple hours in your garage with just PVC and 1/2 aluminum or SS rod, and some pressure treated 2x4 wood.
Something like this works:
You can also add a bridge over the top from PVC to let the sail control line run on like this:
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This gets the sail control line off the back seaters neck (my wives biggest pet peave), but does negatively affect the sails performance a little. It's your choice (suggest making it removable just in case you don't like it).
The holes for the alum rod are just drilled thru the 1 1/2" PVC and shoved thru, I then shoved some wadding into the tubes and filled with either epoxy or fiberglass resin to make everything strong enough (you can see the resin in this pic):
Make sure you use pressure treated 2x4 for the mounting boards (my first set were just regular pine and only lasted a month), I just drilled 1/2" holes in the ends of the board, poured some marine epoxy into the holes then jammed the alum rods into the holes (they will never come out). I then vacuum impregnated the 2x4's with West Systems epoxy that I thinned down to water consistency with denatured alcohol). Basically you put the board into a baggie dripping with the thinned resin then suck all the air out of the baggie with a vacuum, this impregnates the wood forever making it like 3 times stronger and will never rot (this step is optional and way over redundant), just as easy to just brush the thinned epoxy on and call it good enough.
Now the motor mount you just made is only a place holder for the motor, it can't withstand any rotational stress from the motor at all so you have to brace the thing by other means to withstand the rotational stress caused by the motor. I ended up using spectra string (that grey rudder line you can get from Hobie), I use that stuff on everything, and it literally lasts forever a can withstand about 400 lbs of force without stretching or breaking (amazing stuff).
This pic shows the spectra re-enforcement lines going from the motor shaft to the fittings in the hull just behind the motors (formerly for the twist and stow bungy (no longer used)).
That little tiny grey line believe it or not is 4 1/2 yrs old with way over 6000 sailing miles on it and it still going strong (literally it the same exact piece of spectra string I installed originally on my TI back in spring 2010). That little string is all that is needed to counteract the rotational forces from the motor. I also have safety clips and lines on the motor in several places to make sure the motor cannot fall off and get lost (I've lost about a half dozen engines that way (used to race on the mississippi and would hit stumps at high speed all the time many years ago so now I'm anal about loosing my motors)).
There are quite a few motor mount designs that are way better than mine that guys have posted on these forums, I call mine a po mans mount (costs about $15-$20 bucks to make and 2-3 hrs of time in your garage with a hack saw and drill).
Here is a pic of my original motor mount I made the first evening I owned my first TI (after me and wife got caught out at sea when the wind died and the tide was going out on the first day we owned the boat( I got a free ticket from her to buy a motor (LOL), hint: a sure fire way to snooker wife into the motor you wanted to get anyway LOL), that darn motor mount sufficed until I recently built a dual motor mount recently, it's now hanging in the garage as a backup (still works fine):
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Of course the original motor mount is all rusted out (I used 3/8 dia mild steel (not recommended)) but 4 1/2 years and a gazzilian miles later it's still going strong.
Unless your planning on going seriously offshore (ocean) and/or long distances, or you sail mostly in very low winds (like me), I'd can the motor (they are a bit of a pain). or keep it strictly as a safety back (what mine are really for, because we go way offshore scuba diving a lot).
I'm not recommending the dual motor setup, it was a lot of money with few rewards, the boat still only goes about 10-12 mph at WOT (without sails up) and that's about it, if you wanted to go faster you would need twin 5hp motors (or more), and there is no way the AI or the TI could withstand that much weight and torque, even a 60 lb single 5hp motor would be too much for the boat ( IMO), my 2.3hp Honda's weight 27 lbs ea) and that's about max, it's well balanced so I can run without the AMA's, but why would you want to..... If you want to go fast just get an inflatable ( like a zodiac) with a 25hp electric start Merc and a proper steering console (I've see a lot of those around, and they would fit in my garage and on my trailer just like what I have now probably for less money), just bein honest.
Bob