I have a new to me Johnson 1975 25HP, 25R75B. I am unfamiliar with these older engines. So I come to you experts for guidance. History of the engine. The engine looks immaculate... however... the engine sat in at shop after work completed, tune up. Maybe a year or so, shop owner was unable to get in touch with past owner did not pay and moved away who knows. I paid the bill plus very little, and there loss became my gain and another headache. So here's my potential problem, it fires up idles kind of rough. I cleaned carb out, idles better. The lower seeps a good amount of gunk/oil out of every orifice leaving a good top layer in the drum after running. Eventually after a few minutes of running it stalls. Ill leave it there for your much appreciated guidance. Thanks in advance for all your input.