Excellent.... you just went up to the base of the backstay chainplate. Any though of reinforcing that area near the rub rail? How about the trim angle, are you able to get the shaft perpendicular without interference with the rudder?
Yes, I only needed to go up to the chainplate. I'm using an adjustable split backstay so I don't need any reinforcing but i'm fairing in the transom area where I cut with epoxy. I'm perpendicular with the motor shaft but I have a 1/2 inch thick backing plate (hardwood) on the motor mount at the transom. You can see it in the second picture.
Thanks.... really a nice job. My dock neighbors C27 modified his opening for a Yamaha 9.9... but he cut down also... I guess he wanted the hatch cover to function normally... which I think was a mistake.... because he can't get the motor trimmed exactly vertical and that is way more important than the hatch cover.
I've wanted to upgrade my wonderful Tohatsu 2 stroke, but could never justify the change unless I could take advantage of a power trim feature. For all these years I've simply removed the cowling to kick the motor up into the opening and store with a canvas cover. Got so used to it that the modification went way down on the to do list.... but now you've inspired me with what I think is an excellent solution. I have a single backstay setup, so I considered bracing the chainplate with a horizontal piece that would distribute the load a bit.... However, with your somewhat arched cut I think that must not even be necessary.
My next task is to compare the Tohatsu and Yamaha's dimensions..... the Tohatsu would be my first choice if they are the same..... no slight to Yamaha, just my preference. Anyway, thanks a lot for posting your project.
I mainly did this modification to get the motor completely out of the water when sailing. The drag was bothering me and since I sail only in the Ocean I wanted the motor tucked up and in as far as possible with the cowling on. The hatch functions normally and there is plywood core in the hatch cover so I have no problem standing on the modified hatch (200lb). Also nobody sits in that area anyway. i'm making a soft cover with snaps to go over the hole.