Mercruiser...Do I plug the Hole?

[bigeasy1]

Island,
I would cover the hole.I have the Mercruiser cutout pattern for all the Mercruiser drives,and would gladly make a copy and send it to you.
It's a full size paper pattern,and gives you all the bolt placement markings,along with the driveshaft centerline markings for the placement of the pattern.It also gives you all the X dimensions and transom angle measurements.It covers all the alpha and bravo drives.

I replaced the transom in my Tsunami I/O recently,and did it from the inside.I used marine plywood,and bedded it to the outer skin, and covered the hole.I did lay up two layers of 1708 to the face of the outer skin,to beef it up a bit before i put the core in.

After it cured,i glassed over the new plywood on the inside with a few layers of 1708 and tabbed it all into the hull. inside.
Remember,the transom thickness has to be between 2 to 2-1/8" according to mercruiser specs.

Here's a few pics of the old and new transom and old and new engine beds.

*******If you want that pattern just send me a message,and i'll get it out to you.******

The pics are
#1- original transom and engine beds
#2- fabricating the new transom
#3- installing the new transom
#4- laying up layers of 1708 on inside
#5- finished glass work
#6- done and gelcoated