I adapted an EJ22 into my houseboat. Made my own adapter from 1/2 aluminum plate to bolt up to an OMC outdrive with GM pattern.
First, I got the plate drilled and bolted to the Subaru. Then made an a crank adapter for the OMC drive yoke from aluminum plates bolted together, then turned round.
I then made a plate that would bolt to the crank adapter (GM pattern) with a 1" wide wing about 15" long off one side.
Then I cut the heads off some 3/8" bolts and turned the ends to a sharp point. I did the same with 2 dowels.
I went to the junkyard and found a GM 4cyl. with the correct pattern and set it up with the rear facing up.
I bolted my plate to the crank, threaded the sharpened studs into each of the bellhousing bolt holes, and rotated the engine around till the wing was over the point, and gave it a bop with a hammer.
This gave me a perfect punch mark exactly from the center of the crank for each set of bolt holes and dowels.
Then I took straight and diagonal measurements between all the stud points.
Then I drilled a tiny hole through each of the punch marks on my plate wing, just big enough to get the tip of a scribe through.
I mounted that on the EJ and then scribed a small arc on the adapter plate in the general location of each hole while rotating the crank, thereby keeping all the perfect distance from center.
I then laid out the exact centers with the other measurements, cross checking.
It may not be machine shop perfect, but if not its damn close! Close enough for a marine outdrive anyway.
This really worked very well. The EJ22 was close enough to the 140 HP that was originally in there, that the prop was fine.
But... the bigger problem is the exhaust. Nobody makes a marine, water-jacketed manifold for a Subaru. You will have to make your own.
I got by with a fabricated y-pipe that just ran up and over the transom with a muffler on the end. I heavily wrapped the whole thing to keep from burning a hole through the bottom of the boat. But it still got too hot, even with no engine cover, to go over 1/4 throttle for more than just short bursts.
I bought a stainless turbo header that I was planning to weld a water jacket around. But I ended up just recently taking the whole works out because I really needed the interior space it was taking up.
For the time being, I have a Honda outboard mounted, but a custom EJ outboard is on the drawing board!
Edit: the only place the starter would fit with my outdrive was all the way on the bottom. I could not access it easily, so I rebuilt it before installing!
Edited by Subaru Scott, 19 August 2017 - 01:10 PM.