Having some perplexing issues with an 19865 or 86 Johnson 90 HP VRO (see thread in in what year forum) that I am trying to narrow down. The issue centers on a bogging and shuddering/stuttering under acceleration that I am having a h&!! of a time figuring out. I am not trying to write a book here, but probably best to show what I have done to give a better overall picture.
When I first put the boat in the water for the initial shakedown test, started out fine for about the first 5 minutes. Wasn’t coming up to full speed and certainly not singing like usual. The revs were only about 4500 (motor shows as 5500 redline), but then it just started bogging down and dying under power. Still ran in idle but would not accelerate when in gear. Tried to pump the ball but wouldn't stay firm.
Dragged it out and went about checking the usual culprits. Fuel filter was clean, but bought a new one. Took off the carbs, cleaned them up, blew out all parts and rebuilt as it had been a few years. Noticed that the primer solenoid had a small gas leak so I bought a repair kit that included gaskets, valve, o-rings, etc. I also replaced some of the internal fuel lines and vacuum hoses. I did NOT replace any of the fuel line from the portable tank to the engine as this was done 2 years ago. Took for another test cruise and was even worse than before. Pumping the fuel bulb didn’t help at all, and neither did pushing the primer.
Dragged it back, again, to start the next round of diagnosis. Because it was bogging and seemed fuel starved, I was sure it was a fuel issue. Had no way to check if the tank vent cap might be clogged up (10+ years old), so I bought a new gas tank. Checked the fuel line hose and discovered that ethanol had done its nasty job. The inner lining (sierra assembly) had pulled away and collapsed, so this was replaced. Also pulled the carbs again as saw a small fuel leak. Opened them up and found 1 of the frost caps had come loose, and two of the vacuum lines between the upper and lower carb had torn at the nipple - fixed. The fuel line pumped up hard, the clear filter filled and held gas, engine started right up. The idle was still a bit rough at times and sputtered every little bit, but not entirely out of normal.
Took it out for another shakedown cruise. Started up fine, would get underway but as soon as I went to about 2,000 rpm's the bogging came back as did the shuddering. Would eventually get up to about 3500 at full throttle but felt terrible like it has emphezema. The idle was back to rough, acceleration thereafter was tepid and the strange part was it came and went, not consistent. Pumping the bulb or primer did nothing at all. I have exhausted all of my fuel related diagnosis.
Now I am at:
- Power Pack? One of them was previously replaced, different colors - one blue, one black. A ground on the black was showing some corrosion and only hanging by 1 or 2 strands. I replaced with a new connector and took out again, a little better, but not much. Also strange that now the tach was not working so couldn't tell the rpm's. Would the power pack cause an intermittent issue, drop out at higher rpm? Or just not run at all?
- Plug wires? Not sure last time replaced, easy enough to order
- Coils? Didn’t have a multi meter handy and in middle of day, so couldnt see if a spark. Would these cause an intermittent problem, be weak or just not work, so running on 3 cylinders vs 4?
Any ideas to help diagnose? I took a video of the boat accelerating but have to find a way to upload.
Thank you
When I first put the boat in the water for the initial shakedown test, started out fine for about the first 5 minutes. Wasn’t coming up to full speed and certainly not singing like usual. The revs were only about 4500 (motor shows as 5500 redline), but then it just started bogging down and dying under power. Still ran in idle but would not accelerate when in gear. Tried to pump the ball but wouldn't stay firm.
Dragged it out and went about checking the usual culprits. Fuel filter was clean, but bought a new one. Took off the carbs, cleaned them up, blew out all parts and rebuilt as it had been a few years. Noticed that the primer solenoid had a small gas leak so I bought a repair kit that included gaskets, valve, o-rings, etc. I also replaced some of the internal fuel lines and vacuum hoses. I did NOT replace any of the fuel line from the portable tank to the engine as this was done 2 years ago. Took for another test cruise and was even worse than before. Pumping the fuel bulb didn’t help at all, and neither did pushing the primer.
Dragged it back, again, to start the next round of diagnosis. Because it was bogging and seemed fuel starved, I was sure it was a fuel issue. Had no way to check if the tank vent cap might be clogged up (10+ years old), so I bought a new gas tank. Checked the fuel line hose and discovered that ethanol had done its nasty job. The inner lining (sierra assembly) had pulled away and collapsed, so this was replaced. Also pulled the carbs again as saw a small fuel leak. Opened them up and found 1 of the frost caps had come loose, and two of the vacuum lines between the upper and lower carb had torn at the nipple - fixed. The fuel line pumped up hard, the clear filter filled and held gas, engine started right up. The idle was still a bit rough at times and sputtered every little bit, but not entirely out of normal.
Took it out for another shakedown cruise. Started up fine, would get underway but as soon as I went to about 2,000 rpm's the bogging came back as did the shuddering. Would eventually get up to about 3500 at full throttle but felt terrible like it has emphezema. The idle was back to rough, acceleration thereafter was tepid and the strange part was it came and went, not consistent. Pumping the bulb or primer did nothing at all. I have exhausted all of my fuel related diagnosis.
Now I am at:
- Power Pack? One of them was previously replaced, different colors - one blue, one black. A ground on the black was showing some corrosion and only hanging by 1 or 2 strands. I replaced with a new connector and took out again, a little better, but not much. Also strange that now the tach was not working so couldn't tell the rpm's. Would the power pack cause an intermittent issue, drop out at higher rpm? Or just not run at all?
- Plug wires? Not sure last time replaced, easy enough to order
- Coils? Didn’t have a multi meter handy and in middle of day, so couldnt see if a spark. Would these cause an intermittent problem, be weak or just not work, so running on 3 cylinders vs 4?
Any ideas to help diagnose? I took a video of the boat accelerating but have to find a way to upload.
Thank you