I am in the process of replacing the rotted stringers, floor and transom on my Baja 190ES with mercruiser set up.I will be running a 5.7 alpha one set up. Nothing fancy. It will even have the exhaust routed via outdrive. See the pic for my motor mount design. If I can upload it.
Motor mount design for mercruiser set up. I have been critiqued fairly hard on another forum for this. I do not like the idea of lag bolts just screwed into the top of the stringers. Later on they get loose due to vibration and torque. Plus there is no shear as the lags are holding from the top. My design will add strength and reliability. I will locate the engine coupler just as you would with using lags and the alignment bar. People are saying I will lose my adjustability. I have challenged their comments and they have no sound answer to support their comments.

Lags didn't make sense to me but aside from an offshore style Mount I couldn't find anyone doing otherwise.  I didn't want to reinvent the wheel

Lags didn't make sense to me but aside from an offshore style Mount I couldn't find anyone doing otherwise.  I didn't want to reinvent the wheel

I figured you would respond. I was hoping you would see this and maybe get an idea. I love to re-invent the wheel cause the boat builders are not always right. Look at all the rotted stringers, decks and transoms out there. Tons and tons of them. This is because boat builders used junk wood products and inferior glassing process and the biggest fopar is the foam under the deck that soaked up the water rots everything as well as clogs the drains in the hull. My boat will be twice as strong and three times lighter than it ever has when I am done. I don't want any problems with the stringer/engine mounts hence the design I am going to use. I will post them when I get to it here.
T.J.

I figured you would respond. I was hoping you would see this and maybe get an idea. I love to re-invent the wheel cause the boat builders are not always right. Look at all the rotted stringers, decks and transoms out there. Tons and tons of them. This is because boat builders used junk wood products and inferior glassing process and the biggest fopar is the foam under the deck that soaked up the water rots everything as well as clogs the drains in the hull. My boat will be twice as strong and three times lighter than it ever has when I am done. I don't want any problems with the stringer/engine mounts hence the design I am going to use. I will post them when I get to it here.
T.J.

i totally understand.  i have the 2 "pods" that are separate from the stringers themselves that the motor sits on and the mounts get lag bolted into those.  the top cap is like a 1" thick piece of plywood with a crapload of fiberglass on top and sides.  when i was replacing floor and transom i drilled a couple test holes in the top cap and low and i got solid wood so i didnt feel like replacing them. 

from your description and pictures it looks like yours sit directly on the stringers.  i could totally understand wanting to reinforce that area as the size lag bolt used is at least 3/8 of the total stringer size.  i think your plated stringer deal with the sunken threaded holes is a great idea.  i dont see why you'd lose any adjustability in the front mounts by doing it your way as long as your mounts are located in the right spots.  if anything you'll get more adjustability and reliability as loosening the lag bolts to move the motor side/side for alignment eventually will elongate the holes themselves and then once they're loose the motor will move and throw off alignment.