Re: 1973 evinrude power issue
Did it do this since the day you bought it or has anything changed?
1. Order a manual - preferably the original factory manual - see kencook.com or marineengine.com
2. Compression test
3. Spark test - look for a sharp blue spark across a 1/2" gap (spark tester, couple bucks at auto parts store).
4. Inspect the fuel lines & fittings, replace any that are stiff or worn.
5. Unless you know the gas is fresh, replace it with 87 octane mixed 50:1 with tcw3 oil.
6. Look closely at the carb, fuel pump and fuel fittings while you pump the primer bulb, see if you can see any fuel seeping out anywhere.
7. With the engine idling on the muffs, pull, and then reconnect, the spark plugs one at a time. If RPM's don't change noticeably, that cylinder's not making any power. Use a spark plug boot tool to avoid electro-shock therapy. Or ask someone you don't like to help out.
8. See if pumping the primer bulb while under way improves RPMs.
9. Adjust your slow-speed mixture following the directions found here:
http://forums.iboats.com/showthread.php?t=167352
10. Change the water pump impeller and lower unit oil.
11. For future reference, use only champion UL-77V spark plugs.
12. Inspect the propeller for damage.
report your results
