Higher octane?

[capt. sandpaper]

I recently replaced the cylinder head cover on my 69 20 hp Johnson (20r69b), I bought a used one from a person I trust. They tell me I might get a little more hp out of it as it's for a newer model and has less surface area, more compression. It works and there is defiantly some extra zip to it now. It has been brought to my attention that I need to run a higher octane fuel. When I ran it with the higher octane it started with no problems, with regular fuel it becomes difficult to start. Is it just the lower octane? do I need different plugs? bigger fuel pump? OR am I just over thinking it and just need to spend the bucks on higher octane?

 

[Chinewalker]

Re: Higher octane?

I would just run it as you had before. You can "read" the plugs if you're worried about it. They should be a nice, light chocolate color after a good, hard run. If they're leaning towards white, or show deposits of any sort, then, you may need to go higher octane. Chances are you won't have to change a thing. I've run a 25hp based on the old 22-cube powerhead (like yours) and it has the "higher" compression head, etc. Never had a problem running 87 octane pump gas in it...

 

[capt. sandpaper]

Re: Higher octane?

Thank for the reply. I went and checked my plugs, they are fine (I did re gap them though) and started the motor again. It took a few cranks, considerably less though. Not sure I have to double check, but could it be that I crossed the plug wires, effecting the initial start up?