Am I Really This Stupid?

Just took a 1966 Johnson 5 horsepower in on a trade in where the guy had it "repaired" and it would not give him any power at wide open position. Before the repairman had it, he did have full power but the throttle would not stay in position because there was not enough tension apparently on the stator plate mechanism. As most of you techs must know this is a non-reversing lightweight version of the 6 horsepower. I did a compression test and it is between 65 and 70 lbs. I found that the guy had replaced coils, points, condensers, and rebuilt the carburetor. The points needed alignment and proper setting and the small donut gasket at the base of the carburetor bowl was missing. This would account for the motor running quite rich and unable to build speed, however it did idle pretty well. As you may know the five horsepower uses a smaller bore carburetor but otherwise almost the same version as the six horsepower, with the 41 main jet. After replacing the donut gasket, making sure we had a good seal, it started immediately, but still wouldn't build speed ....running rich, both cylinders at about 150 degree operating temp. By the way I had to put in a thermostat as there was none in place. Whoever put the new thermostat cover on must have thought it would run better without a thermostat....HA! It is a very low hours motor in beautiful condition. So I checked the orifice bore on the main jet thinking it was reamed out but no such luck, it is the correct bore. Next I tried a 6 hp carburetor with the larger throttle bore and also the number 41 main jet and the motor runs better but I have to put my finger partially over the choke opening before it will speed up to full throttle. Of course it will not idle now worth a damn with low speed needle set at 1 1/2 turns open with this carb.
So what's wrong? Did the guy mess with the timing? It seems to have all the original parts and throttle advance ramp. It really idled good with the 5 hp carb, but the low speed jet was completely closed. Note: no leak of fuel pump diaphragm into the crankcase.
Please help....but hey, I don't expect anyone to figure this one out on first guess.

Are you sure the orifice plug is supposed to be #41? Doesn't sound right to me with that little bitty venturi size. Now where did I put that chart???

BTW, the 5hp came from the factory with no thermostat. Then they sold a thermostat kit as an accessory kit.

Thanks, Gator. I checked with Tim's Outboard in Hackensack Minnesota and Dan checked his information and said the 41 is recommended. I sold the motor already on eBay and it's going to Hilo Hawaii for a dingy. I really feel stupid I can't figure this problem out. I certainly didn't know the 5 came without a thermostat. That is really "cool" information. It also has the larger fuel pump which is uncommon for this powerhead. The water pump is original and pumps water like mad. In those days the impellers were real latex rubber. I have to open it up and check it because the lower unit will be packaged alongside the powerhead to minimize box size. The replacement impellers are garbage when compared to these 1960's units.

I believe 1967 was first year for the little square pump.

Thanks. So Racer, any ideas on my dilemma here?

Inspect reed valves.----If it has the original head gasket then remove cylinder head.----Inspect cylinders.----Inspect head gasket.-----Install improved version ( sierra ) head gasket.

Excellent advice....will pursue these tasks immediately. Much appreciated, will report back soon.

Immediately? Wrong!.....Life happens! Okay, finally got to it. What do you think of these reeds? Could this be the problem? Doesn't make sense that it ran wide open before the guy worked on the stator, unless he left it out in the rain for 3 weeks.

This just proves again, that no matter how good a mechanic a person might think they are, there's always somebody better....thanks Racer! I owe you a Hamm's!

Still just exactly the same symptoms. Could it be a leak at the little tube connecting upper and lower bushings? I see bubbles going through the clear tube. The original tube had a crack in it, I changed it.