50 HP Evinrude 4 Stroke sluggish

[brian6464]

Let's get this out of the way first...I have very little motor experience. Hence my reason for the post.

I have a pontoon with a 1999 50HP Evinrude 4 stroke that runs perfect at low throttle. The engine is quiet and provides a smooth ride. When I start punching it down to full throttle, it starts missing. For lack of a technical term, it get herky-jerky. I just had the impeller replaced at a shop and it seemed to run fine prior to the service. It's new gas also, so that should not be an issue. This behavior was observed the first time back in the water following the impeller replacement.

The pontoon is a 1996 and the guages do not work properly, so I cannot give exact rpm's where the engine performance deteriorates.

Are the most likely issues (1) clogged fuel filter or (2) bad spark plug(s) ? Could the shop have messed something up during the impeller replacement?

I appreaciate any input and ideas where to focus my attention. Thanks!

 

[daselbee]

Re: 50 HP Evinrude 4 Stroke sluggish

To me, you are describing the rev limiter kicking in. Does it surge - fast slow, fast-slow? If so, that is the rev limiter. It's cause is quite often a sticking neutral safety switch. It is located on the shift linkage, very near the point where the linkage arms pivot/rotate. Follow the shift cable to the point I am talking about. You will likely have to remove the stbd side cover to see. Switch will have two wires, and a semi-circular chrome steel shield over it that acts as the surface that the linkage rubs on to actuate the switch. Here is the deal: If the engine thinks it is in neutral because the switch is stuck closed, it will not rev above 2500 rpms without being in rev-limit mode. The switch is supposed to go open when the engine is in any gear. It does have an adjustment.