Motor not running right

I have a 1989 25 hp Johnson that I recently did a 30 hp conversion on. I did some work for a guy and he traded me this motor and said it just needed a tune up. I checked compression and other major things and decided I would take it. Since I only had a few hours welding/fabricating for him I think I got a good deal. I took the carb off to rebuild it and it was boogered up pretty good. Someone had tried to rebuild it before and used the wrong tool to take out the jet and stripped the ears off, the lead shot had been pounded down in the carb, and the flap was bent somehow. I found an older 30 hp johnson that had the bigger intake and carb and did the swap after rebuilding that carb. The motor runs great at WOT and at idle, but when I come down from WOT to a slower speed, it seems to pop, sneeze, snort and blow about mid throttle when the bow is up in the air some. Could this just be the wrong float setting. I set it like I have always set one on my older (mid 70's) Evinrude. It seems to be getting too much of something in that particular throttle position ONLY on deceleration. It accelerates just fine. Any ideas?

Ok did you do the carb and intake swap to make it a 30hp? And what year motor did you get the parts from? If you just threw a 30hp carb on it without the larger volume intake then you could be getting to much fuel to air mix. The lead shots you are speaking of are welch plugs/freeze plugs I am assuming, and them being pounded flat or indented is normal. Did you do a complete carb rebuild....including replacing the welch plugs, slow speed idle packing etc.? Float should be parallel to carb body when upside down, that is the correct float adjustment on that motor.

Also being sure it has the correct link and sync could very well be your problem, or even proper slow speed idle adjustment. Do you have the OEM manual for your motor?

I did the carb and intake to make it a 30. The intake and carb came off of a mid 80s motor and has the slow speed idle on the front (long needle valve with black end). The original carb was ruined the best I could tell. I do not have a manual of any kind. I followed the steps I found on here for the link and sync. The float is parallel to the body. I am familiar with rebuilding these carbs, my old one was close to the same. All welch plugs were removed before cleaning and replaced afterwards. I read on another forum that they could be leaking if I didnt get them seated right. Any thoughts?

yes they could be leaking if not seated correctly. I usually set them with the rounded blunt end of a ratchet extension, using it like a punch to indent and seat then well. One good whack usually does the trick.

Do you have good plugs? What is your fuel mix ratio you are running? Did you set slow speed idle adjustment while engine was in the water, on the boat, in gear at lowest idle? And did you check reeds when you did conversion, and did you replace intake manifold gasket, carb gasket and reed plate gasket when you did conversion?

Normally a sneeze or cough is caused by a lean condition. You should also check your reed valves. Hope this helps.