I have been using my Johnson now for many trips this summer, it´s been running flawless until few days ago..
On the way home I cruised at 3000rpm for a while and when I started to throttle up it suddenly started hesitating and lost power, it newer reached 4000rpm and just boged down to even less than 3k. There are some very short bursts with normal operating but they last for less than two seconds and then bogs down again.
From what I can hear, it sounds "normal" at idle and runs ok at less than 2500rpms.
Done so far:
- Compression test with the following results: STBD: 2x120 PSI PORT: 2x125 PSI
- Tested with different tank with fuel.
- Spark plugs looked equal, they were all new for this season (according to new information they where wrong ones due to a bad translation made by NGK, BPZ8HS10), changed to new plugs again after the issue started (still NGK but MORE correct acc. to a mechanic), New Champions QL78YC are on the way.
- Ran the boat whilst pumping on the primer bulb, but the issue remained
- Tested with ignition timer gun to see of any ignition cable stops pulsing completely (none stood out or stopped giving signal from idle up to WOT).
- Removed all carbs, found a really thin piece of membrane-ish dirt inside one high speed jet screw, no change after cleaning.
- A small deep scratch on one of the floater pins where also detected, looks man-made by previous owner perhaps, but I can´t feel that the scratch effects the function of the floater. See Pic.
- Checked that there was spark at all plugs when in neutral and did a test with homemade spark tester to see of it could jump 7/16" gap in neutral (OK), I will also later test if it continuously jumps when moving the gas to WOT without change of intensity..
- One ignition cable cable cap (on spark plug) give me a shock if touched.. none of the other caps does this, any thoughts? (a new cap will be installed on the existing cable).
Movie of the idle: https://www.youtube.com/watch?v=0l1ROKyGdmA
Can the power pack be ruled out yet?
What different issues could cause this behavior and what is the most likely cause?
Best regards Stefan
On the way home I cruised at 3000rpm for a while and when I started to throttle up it suddenly started hesitating and lost power, it newer reached 4000rpm and just boged down to even less than 3k. There are some very short bursts with normal operating but they last for less than two seconds and then bogs down again.
From what I can hear, it sounds "normal" at idle and runs ok at less than 2500rpms.
Done so far:
- Compression test with the following results: STBD: 2x120 PSI PORT: 2x125 PSI
- Tested with different tank with fuel.
- Spark plugs looked equal, they were all new for this season (according to new information they where wrong ones due to a bad translation made by NGK, BPZ8HS10), changed to new plugs again after the issue started (still NGK but MORE correct acc. to a mechanic), New Champions QL78YC are on the way.
- Ran the boat whilst pumping on the primer bulb, but the issue remained
- Tested with ignition timer gun to see of any ignition cable stops pulsing completely (none stood out or stopped giving signal from idle up to WOT).
- Removed all carbs, found a really thin piece of membrane-ish dirt inside one high speed jet screw, no change after cleaning.
- A small deep scratch on one of the floater pins where also detected, looks man-made by previous owner perhaps, but I can´t feel that the scratch effects the function of the floater. See Pic.
- Checked that there was spark at all plugs when in neutral and did a test with homemade spark tester to see of it could jump 7/16" gap in neutral (OK), I will also later test if it continuously jumps when moving the gas to WOT without change of intensity..
- One ignition cable cable cap (on spark plug) give me a shock if touched.. none of the other caps does this, any thoughts? (a new cap will be installed on the existing cable).
Movie of the idle: https://www.youtube.com/watch?v=0l1ROKyGdmA
Can the power pack be ruled out yet?
What different issues could cause this behavior and what is the most likely cause?
Best regards Stefan
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