Bones, There is a non adjustable bolt on motor mount that appears to be rock solid, extremely strong and bolted down well. However, I've not looked to see about the backing plate. Funny though... When I frequented the Potter Forum, there was discussion about leaving the motor attached and several people chimmed in to tell horror stories of seperated seams, large cracks, etc. Guess there are more differences than I thought. I read an article in Good Old Boat magazine that stated... It's better to have a smaller engine running at 3/4 throttle that to have a larger enging running at half throttle. Small gas outboard engines are designed to be rev'd a bit and will load up and run hotter at slower speeds. I'd think the 4HP would be just a little small for the 23? Then again if you're not fighting currents, it's probably just right. The current OB on my M-17 is a 2-stroke 6HP. California has most of it's better lakes on a 2-stroke ban, so when I get to lake use, I'll be looking at a 4-stroke to replace the current outboard. I'm just beginning to start a short list on replacements and weight will be one of the deciding factors. Bill M-17 SF Bay