Wont reach full RPM under load? 1974 9.9 Evinrude

[Bubbles Up]

Hey Folks,

I finally got to take my '74 Evinrude 9.9 for a spin today,
At the start of the day it would hit TOP rpm at WOT, I could feel a bit of a surge but figured it would be just from sitting for the winter/spring. I did a bit of trolling then went to head back to the launch the engine would rev up with no load, as soon as it was in gear the I was lucky to get to about half throttle anything above that, it would not do much . Any ideas???

 

[kbait]

Check spark when it's not performing. Likely one cylinder isn't firing correctly due to cracked coil arcing to ground or dirty/pitted points. Google 'leeroy's ramblings' and look over his 9.9/15 articles. TONS of great info there!

 

[F_R]

That model is absolutely NOTORIOUS for fouling spark plugs. On some boats we couldn't keep brand new ones running for one weekend. Sorry to jump to conclusions, but I'm betting on a fouled plug. Better keep a box of 'em handy.