'91 Johnson 48hp SPL

I need help troubleshooting an issue:

I have a '91 Johnson 48 SPL. It starts right up, but idles a little rough. Also, it seems to have a minor misfire. It still pushes the boat in no wake, minimum wake zones.

However, when I increase the throttle to plane, to the boat will jump out of the water to go, but will suddenly lose its RPMs and go back to jogging. Also, when I am at about half-throttle the RPMs will suddenly increase and then subsequently decrease.

What I am thinking - issue resides in the carbs, gas/throttle issue, and/or power pack/coil pack. I recently purchased the outboard and the mechanic was suppose to ensure that the carbs were clean and the water pump was good, as well as wire the control box. However, I am thinking he may not have checked the carbs at all.

Where should I start? I appreciate any and all of your help.

Thanks.

Re: '91 Johnson 48hp SPL

You can use an inductive timing light to check the spark when it is missing. You could try pumping the primer bulb when the problem occours and see if it helps, this would bypass the fuel pump. If you are not loosing spark and pumping the primer bulb doesn't help, it sounds like it might be time to overhaul the carbs paying attention to the idle and high speed orifices.

Re: '91 Johnson 48hp SPL

Thank you for the information. I will give that a try. Like I said, the mechanic was suppose to perform and overhaul to the carbs, but after my third time leaving it with him to troubleshoot, he told me that he basically "didn't know what was going on..." He did mention that the coil pack is bad, and when I asked questions about how many, etc., he replied two and that he couldn't remember which one it was...The spark plugs look good, but they will be replaced anyway.

I have heard/read about the fuel enrichment (?) switch being switched to a certain position, and that it may be running too rich. Currently, that switch is facing the carbs. Should it face the other way? Or is this in the correct position?

Thanks, again, for the information.

Re: '91 Johnson 48hp SPL

Daviet - After much time and effort, I have my boat on the water and running well. In your efforts to assist future issues, I wanted to share with you all that I did to get my boat back up and going. While I am not sure which action may have completely fixed the issue, it works now and that is all that matters.

-Changed out fuel system from the gas tank to the fuel pickup on the outboard.
-Changed the fuel pump.
-Checked recently rebuilt carbs and found pieces of something in there. Pieces of the old fuel pump? Hose? Tore down the carbs and rebuilt.
-It still was not running at this point, though, so we went to spark, which seemed fine and went on to stator and coil packs. Went back to the timing and reset that.
-Added a fuel filter and water separator and pumped fresh non-ethanol gas into the system.

She's alive!!! My video is too big of a file to post.

Only problem is I have some over-revving at/near full throttle. I think it is my prop, though. It is stainless but I am seeing where it has been re-welded on one of the blades. So I will add a dolphin tail and check different pitches of prop. I think mine is a 17-pitch...

Thank you!