I recently bought a 1991 Johnson 48 hp SPL, model J48ESLEIM. The seller informed me of a "bogging" issue after it warmed up, but I figured for the price, it was worth it for the learning experience. The boat cranks up and runs great for the first 10 minutes or so at WOT, then the motor loses all power as if its been throttled down to idle speed. It does not stall out. It continues to run and once the the throttle/shifter is brought back to neutral, it will run fine at around 1/4 throttle. If I shut it off for a short period of time, it will plane out again, but still lose power when it warms up. The warning horn gives a chirp when the key switch is activated, but no warning horn when motor loses power. It maintains a good telltale stream.
I've replaced the ignition coil, rebuilt the fuel pump, replaced all fuel lines(boat side and motor side), rebuilt the carbs and checked float settings, changed spark plugs, and replaced one of the spark plug wires(found a bad spot in it). Yesterday, I pulled the flywheel and checked resistance readings on the stator assembly. All readings were within limits, per the service manual. Not sure if it could be related, but I did change the gearcase oil in the lower unit, and it did appear to have some water in it. I'm not sure when it was last serviced. I've also got a new water impeller and plan on installing it this weekend, since I don't know the age of the current water pump.
Spark and compression seem to be fine when the motor is not under a load or at WOT.
I'm leaning toward the problem being the power pack. It seems to be original by the part number on the ignition module.
Here is a video from Monday of the problem. Is this S.L.OW mode activating?
http://youtu.be/f95tvwHS7g0
first 2 minutes of the video were edited out of the boat running fine to show the problem.
I've replaced the ignition coil, rebuilt the fuel pump, replaced all fuel lines(boat side and motor side), rebuilt the carbs and checked float settings, changed spark plugs, and replaced one of the spark plug wires(found a bad spot in it). Yesterday, I pulled the flywheel and checked resistance readings on the stator assembly. All readings were within limits, per the service manual. Not sure if it could be related, but I did change the gearcase oil in the lower unit, and it did appear to have some water in it. I'm not sure when it was last serviced. I've also got a new water impeller and plan on installing it this weekend, since I don't know the age of the current water pump.
Spark and compression seem to be fine when the motor is not under a load or at WOT.
I'm leaning toward the problem being the power pack. It seems to be original by the part number on the ignition module.
Here is a video from Monday of the problem. Is this S.L.OW mode activating?
http://youtu.be/f95tvwHS7g0
first 2 minutes of the video were edited out of the boat running fine to show the problem.