Im running the etec 115 ...... unrestored it is heavy .... I think after the transom is raised it will be great !!! but I am still having issues with propping and my mechanics thoughts on rpm I should be able to achieve ... currently I can only turn up 5400 - 5500..... turning a 15 x 17 old 3 blade ... I think I am going to drop to a 14 3/4 x 15 4 blade in the near future...

My mercs 115 4s pushes my 20 pretty well

I just installed trim tabs on my 18 complete resto I have a 150 etec running 3500 rpm at 34 mph and 4.6 mpg

Marks 1971 20 with the Zuke 140 4 stroke was by far the best riding 20 I have been on. No wet feet. My 73 20' with 2 stroke 175hp was way too much power.

Btw: that's me at the helm :p
Check it out --------》http://www.classicseacraft.com/marks20/index.html

I just bought a 150 Etec for my '83 center console. It's a little longer than a Potter and already has a 25" transom. I was looking at the 115, but the 150 was only 26# heavier and is arguably the "sweet spot" in the Etec line and the price was right.
As soon as I finished the raised deck on my Gheenoe, I'll install the 150 and post some results.