91 Force120 - Knocking and Hesitating

[ebjr]

Hey guys,
I've had some issues recently with knocking on my 91 Force 120. The issue goes back some time. A few months ago we had some light knocking with little hesitation and found a broken wire. Crimped on a new connector and the problem went away. A couple weeks after that we had a similar issue but it was hesitating when excelerating. That turned out to be a bad spark plug boot. Put a new one on and the problem went away. Now this past saturday we had some knocking and hesitation when accelerating. We couldn't get the boat to do more than 25mph with out it knocking really hard. The boat would idle just fine but as soon as you got her above 15mph or so she would start hesitating and knocking again. We got home and checked the wires, cables and idle. That all seemed to check out ok. Not sure what else to do.
Any recommendations or does anyone know of a good outboard mechanic around plant city, fl?

 

[Matthew A.]

Re: 91 Force120 - Knocking and Hesitating

If your year Force uses the Prestolite ignition system you may have a blown CDI unit as your description of how the motor runs fits perfect. Idles fine, but runs as if only getting half throttle. You may also want to check for a possible bad coil or coil wire. While nosing around look for loose or broken connections at the terminal block for the trigger harness.

 

[ebjr]

Re: 91 Force120 - Knocking and Hesitating

Hello Matthew,

Thanks for your response.

We checked the coil wires and boots before taking it to the mechanic. The top boot was bad and was replaced a couple weeks ago.

We got a call this morning from the mechanic stating that the timing is way off and needs to be adjusted. He also said the propeller hub was slipping big time and that could also cause the motor to knock or hesitate. Being a novice, that sounds like an honest assessment but i'm not sure.

The prop on this motor is very old, warped/bent and has a few knicks in it so i'm not surprised if its causing an issue. But does the timing on an outboard normally need to be adjusted, is this common?

Thanks again.