Speeds from First run in new 18 hp Copperhead SD yesterday.

That's very solid. What type of boat (length and beam) were you running?

I've got a 15" War Eagle with a 27 prodrive. It's a great boat but the configuration has issues. Namely, the narrow beam and short length causes the heavy engine to draft pretty deep. In fact, the entire boat drafts too deep. I've been thinking about getting a 18hp Copperhead since it is so much lighter just to compare. I've been told my performance would stay the same but it's hard to imagine I could drop 9hp and keep the same speed....

Go to the shop in Covington. Gil and his son Josh will put an 18HP on your boat and take you on a test run in tchefuncte. They said they ran a 12HP faster than one of the traditional mud buddy's. I dont doubt it.
My boat rides smooth on the water and leaves hardly no wake when running. The 18 hp copper head is 135lbs I believe.

Worth a free test drive atleast. They took me out on a saturday too fwiw.

I got a paint job (125) and clutch(300) added on. Then Gil took 200 off due to my intense negotiating tactics.
After taxes I paid 4490.80. Still cheaper than all the other surface drives around.
Spending the money doesnt hurt as bad knowing I can call Gil anytime with issues and he will anxiously resolve them.
Not trying to sound all homer cause I just bought the thing but these guys are good old fashioned hard working americans.
Hell, they even offered me a beer while doing the paperwork.
I would seriously look into calling them and going for a test drive with the motor on your boat.