Originally Posted by
bighare
You are on a good path. Decarboning the cylinders and rings will make a big difference on this engine. Recommend an over night sit in the tilted up position to get the best results.
The double fuel shock treatment may not see benefits since you have already cleansed the major components.
Cranking speed is important for starting. If the starter rotates too slow the magneto does not build sufficient electrical power for ignition. Believe it or not the a good tug on the rope starter, if you have this, will build a faster rotation.
The reed valve pedals are arranged in a circular pattern. One set for each cylinder. It would be unlikely for these to stick closed.
Now let my next suggestion be guided by the idle quality as this fix requires removal of the power head. The exhaust pipe / exhaust tube inside the exhaust housing and attached directly to the engine block directs all exhaust down to the lower unit. This tube also includes strategically placed and sized exhaust relief holes for improved idle quality. These holes are known to plug with carbon over the years. Plugged idle relief holes result in a less than perfect idle quality especially at slow speeds. Cleaning them is not a critical requirement but if you have difficulty finding a good idle mixture adjustment, with the boat floating in the water, you may wish to take the step to pull the powerhead, remove the tube and clean out the holes. An additional benefit is to inspect the impeller water supply tube. The tube is connected to the exhaust tube and block via a rubber grommet. This grommet deteriorates over time by heat and gets restricted by corrosion. The result is reduced water flow causing a high speed overheat.
good luck.