86 Johnson 15 hp disappointing power at WOT

So I finally got a chance to test the motor after carb clean and rebuild, along with lower unit service and new spark plugs. I've been really anxious to test the performance since this is my first outboard. It started fine with just a few pulls but needs a tad bit of throttle to run at idle.

I couldnt wait to test the top end speed but was kind of disappointed when I topped out at 11 mph. The boat is a 14 ft. Alweld so a little on the heavy side. I had another person weighing 150 lbs. A trolling motor, battery, and 15 lbs. anchor, so roughly 385 lbs. In the boat. Is thisnormal?

The compression is 115 on each cylinder. While I know very little about outboards, it seems like it may ne running a little rich. After about a 20 minute cruise, I took a look at the spark plugs, and here is how they look. Is this normal for 2 stroke after only 20 minutes? Something just doesn't seem right. I'm trying to be patient, but after a month of ownership I'm getting ready to enjoy this boat and stop tinkering. Any advice would be great.

Two stroke plugs look nasty like that yes. Sounds like the boat never got up onto plane. What hole is the pin in on the outboard? Try it lower and ditch the passenger and weight to at least see if it's running right and gets on plane. You should be 20 ish mph.

ya most likely need a smaller pitch prop prolly a 6 1/2 or 7 ....

Thanks for the tips guys. Will give it a whirl and see if it helps. I am thinking the problem may be engine related. It is hard to describe but it almost seems like the engine isn't fully opening up. Almost like a ridding mower set to turtle speed instead of rabbit. Not sure if there is anything that can be adjusted, but again it just feels and sounds like the engine isn't fully opening up.

Really fighting the urge to take it to a shop.

With the motor off see if the choke and throttle open all the way. Do you know what your rpm's are at wot?

Tried trim setting on lowest and second lowest position with no change. Motor, trolling motor, battery, and myself were all in the back of the boat. 150 lbs. passenger and 15 lbs anchor in the center.

Choke opens and closes fully using adjustment knob but throttle seems to only open around 80% using throttle (i can open it fully by grabbing the roller and pulling it forward)

Hope this helps you guys help me. I bought this motor used and was told it had been sitting in a garage for couple of years. Carb was filthy so I rebuilt it. Replaced spark plugs just because.

I noticed a screw on what looks like a cam that meets the throttle roller. It was backed out fully. Tightening it seems to extend part of the cam that meets a roller on the throttle body.

It honestly seems that if the cam could advance further, the throttle would open more, but I see no way to do this.

Still trying to learn what everything is called so bare with me. Totally new to all this