Ben Bowden
New member
Hey Guys,
I've got an old 70 HP Johnson 2 stroke which was running great up until a short while ago... Here's the background:
I've been taking it out once a week to drive about a few hours out and back to a surf spot near home for about the last year and in that time I had 1 small problem. Every now and then (maybe once a month and increasingly up until this problem) it would run on 2 cylinders instead of 3 for about 5 mins and then carry on as normal at full power.
I took it out recently and it started up fine. We'd made it about 20m out when she died. I changed over to brand new plugs there and then. no good. got a tow back and could start it and kinda keep it alive if I worked the primer bulb. So I figured it must be a fuel problem. Got it home and it started up fine and did so every time I tried to get the fault back for about the next month. Finally i caught it dying and the primer bulb was deflated and I assume therefore no fuel was getting to the cylinders. I'd already cleaned out the lines up to the fuel pump so I figured that was the problem. Ordered a new fuel pump and hey presto we're back in business and it seemed to be running better than ever in the driveway.
One weird thing that I noticed at this point tho - while idling, about every 5 or 10 seconds, the tell tale would switch from being boiling hot (If it was any hotter it would have burnt my hand) to being cold and then cycle back and forth continuously between these temperatures every 5 or 10 seconds. Is this normal?
Thinking nothing of it we took the boat out and it started and then died shortly after and we were unable to get it going again. We pulled out the plugs and from the bottom spark plug hole, out came some sort of oil/fuel/maybe water kind of mixture.
Any ideas? Is it possible the bottom cylinder was never firing and this was why the tell tale was sometimes cold??!
Most of my logic has come from car engines in fixing this and while I understand how 2 strokes work this is my first time trying to fix it...
Many thanks in advance if you have any input at all
I've got an old 70 HP Johnson 2 stroke which was running great up until a short while ago... Here's the background:
I've been taking it out once a week to drive about a few hours out and back to a surf spot near home for about the last year and in that time I had 1 small problem. Every now and then (maybe once a month and increasingly up until this problem) it would run on 2 cylinders instead of 3 for about 5 mins and then carry on as normal at full power.
I took it out recently and it started up fine. We'd made it about 20m out when she died. I changed over to brand new plugs there and then. no good. got a tow back and could start it and kinda keep it alive if I worked the primer bulb. So I figured it must be a fuel problem. Got it home and it started up fine and did so every time I tried to get the fault back for about the next month. Finally i caught it dying and the primer bulb was deflated and I assume therefore no fuel was getting to the cylinders. I'd already cleaned out the lines up to the fuel pump so I figured that was the problem. Ordered a new fuel pump and hey presto we're back in business and it seemed to be running better than ever in the driveway.
One weird thing that I noticed at this point tho - while idling, about every 5 or 10 seconds, the tell tale would switch from being boiling hot (If it was any hotter it would have burnt my hand) to being cold and then cycle back and forth continuously between these temperatures every 5 or 10 seconds. Is this normal?
Thinking nothing of it we took the boat out and it started and then died shortly after and we were unable to get it going again. We pulled out the plugs and from the bottom spark plug hole, out came some sort of oil/fuel/maybe water kind of mixture.
Any ideas? Is it possible the bottom cylinder was never firing and this was why the tell tale was sometimes cold??!
Most of my logic has come from car engines in fixing this and while I understand how 2 strokes work this is my first time trying to fix it...
Many thanks in advance if you have any input at all
