Motor "Jerking" Hard

[brousard]

I just bought a older used 9.9 HP Evinrude Sportwin. It starts and runs well, but when under power, at times it jerks. The jerk feels like it hit a stump of something, but it has not. It'll go for a shortwhile and then "Bang" another hard jerk. The motor does not slow or stop, it keeps going. I thought the prop might be slipping on the rubber clutch insert thing. I took the prop off and the rubber clutch seems OK. Any idea what is wrong?

Thank you for any help you may can give me.
Bruce
dg_brousard@yahoo.com

[Phil H]

Sportwin sounds old. I am familiar with 9.9's that have through-the-hub exhaust. The prop shaft is splined and there is no shear pin. I would look at the rubber hub on the prop shaft to see if it looks like it has spun. Another thing to watch is the shift lever. If the shifter jumps when the motor jerks, the problem may be in the lower unit. (I don't know how to describe it in lay terms, but the clutch dog could be slipping). The 9.9 lower units are tricky to assemble and re-assemble. If you don't have patience and mechanical abilities, repairing a lower unit is better left to a professional.

Take my advice with a grain of salt. I haven't been around outboards for 10-15 years. But, I have repaired 10-20 9.9 lower units. But, my memory isn't what it used to be. Good luck