Re: age 9.5 hp johnson seahorse (Help)????
You can buy most parts from your local dealer or from BRP-Evinrude on line. Click the diagram at this link and navigate to your motor.
http://shop.evinrude.com/
Most parts that are scarce can be found at sea-way.com in Seattle WA.
Do a search here for "1971 9.5HP"
Most routine service parts are available here at iboats.
The fuel/oil ratio is 50:1 - 87 or 89 US Octane to TC-W3 oil. The plugs were initially J4J which are now superseded by the Champion J4C. Many use a J6C which is a hotter plug.
The engine will run better with less carbon and plug fouling using synthetic or synthetic blend TC-W3 oil.