I have also just replaced the intake gasket and reed plate gasket to fix a vacuum leak. On it's maiden voyage a few weeks back I had forgotten to replace the oil in the lower unit and well, nuff said. It runs fine when operating on the top cylinder only. There's no use letting a brand new impeller sit stationary for months on end. It seems to misfire when I bring it back to idle. This video shows how to take apart the gearcase of an outboard motor and shows how it works, transfering the power from the drive shaft to the propeller, and selecting Forward, Neutral or Reverse.
The method described in this video is not considered a 20 year fix
📺 Byter/demonterar Växelhus/rigg på gammal Johnson 20 hk
You'll see how the dog clutch moves to select forward, neutral and reverse as well as where the exhaust gases flows out behind the propellor. I have never serviced an outboard so this should not be taken as a "how to" video, but it will certainly give you all a rough idea as years and models will vary what you may or may not encounter. Legendariske motormecken Anders "Nypan" Nyström från Yamahacenter i Nynäshamn visar bästa knepen för att ta hand om sin utombordsmotor. The motor was a US Marine Force 50 HP but I suspect this method would work on any outboard with a forward-neutral-reverse gear shifter. I alla fall, här kommer en dåligt redigerad film på hur jag gjorde när jag bytte växelhus på min 20 hk Johnson motor. Anders "Nypan" Nyström delger sina knep för att kontrollera att en begagnad motor är i ok skick.