UPDATE: got home, but before I began working on anything I decided to push the cam roller forward to see what happens. When manually pushed, the engine roars back to life and revs at the appropriate RPMS. When I position the throttle to WOT, the black plastic plate which is meant to press on the cam roller barely nudges it forward before stopping. it seems that it is misadjusted and needs to be moved. I apologize if the description is confusing. I can attach a picture if need be.
Most likely that is because your throttle is limited by a :neutral stop". The neutral stop is to prevent you from over-revving the motor when it does not have a load on it. Believe it or not, when you over-rev the motor, not only can that damage the motor in itself but you can get a runaway motor. I won't go into the technical reasons of how a motor continues to run on when you when you kill spark and turn the throttle to zero, but it can, so be careful.
To see what I mean by the "neutral stop" just put it in gear and you will see that the throttle cam is allowed to push on the carb roller a lot more. Check this without the motor running, if you want to see what I am talking about.
OK, back to your problem. 1st the right position of the throttle cam is that the "arrow" on the throttle cam is in the middle of the carb roller JUST as the throttle cam touches the roller. If it is not, there are two 5/16" hex nuts just below the flywheel on the starboard side of the motor. Loosen them and adjust the throttle to where it should be and tighten them again. Don't bother if it is very close because it is a little more difficult to do then how easily I describe it. You really can't get a standard 5/16" wrench in there. You either have to find a very thin wrench, file down a regular wrench or pull the flywheel.
Lastly, check your cylinder drop test. It is highly likely a spark plug fouled. Probably the bottom one. Those motor hate any Champion spark plug ever made. Champion makes great spark plugs, but not for the 1974-1976 9.9/15Hp series of motors. You need to use NGK B7HS (B6HS if you have a 15hp) or you will be fouling spark plugs very quickly. Most likely your plugs were close to fouling but when you positioned the fuel mix to over-rich before you dialed it down, that rich mixture combined with low RPMs, will foul the standard champions very quickly, on that motor. I mean, if they were brand new, they would probably last more then an hour but if the plugs you had, already had a small film of carbon on them, perhaps 5 more minutes at low RPMs with a highly rich gas mixture was enough to foul your current plugs before you could set the carb mixture correctly. Again, probably the bottom one. It is not OMC's best design but the NGKs tend to fix it quite well. I have both the 9.9 and 15Hp and find them to be totally reliable.
Anyway, a dropped cylinder may not be your problem, but the NGKs will keep you from rowing. Also, don't use that motor for long trolling sessions. It really does not like low RPMs. Run that baby hard and fast, with NGKs and it will never let you down. Run it slow, with Champion plugs, and keep the oars handy.
