Hello,
I have been trying for two years to get our old 72 Johnson running right. I pretty much gave up last year, but got back into it lately. The engine sat for 17yrs, but was in good shape with low hours when it was put away. I got it running last year with a new CDI pack, coil and rectifier. The engine starts, sometime picky when cold but once warmed up, starts right up. But when lake testing, it won't plane out, when you rev it up, it starts to miss and bogs down. I have cleaned the distributor and rotor with emery paper, and its a little pitted in a few spots, but I don't think that should matter. I have re-terminated the plug wires and they ohm out good. I have been through the carbs a half dozen times. This year has fixed jets and no adjustments. I have checked compression, all about 105-110.
Last night I decided to pull the flywheel and adjust the sensor (original 1972), I moved it from .028 to .020. When I started the engine, it fired up on the first crank, and fast idled pretty good. I opened the throttle fast start lever and at a certain high rpm, I noticed the engine began to shutter and miss. I have an induction timing light that I've used to test with and noticed that all plugs seem to fire regularly up to this rpm and then the timing light starts cutting out, and flash brightly irregularly during the miss. The motor also smokes a lot. If you ease the throttle back down below this threshold, the timing light acts normal again, on all cylinders fire and no miss. Has anyone seen this before, and do you think that I have a faulty timer base sensor? I hate to keep putting money into this old boat, but I also hat to scrap it after spending the money I've already spent.
All along I've thought the plugs looked too wet, but since there is nothing to adjust on the carbs, but the float level, I conclude that it must be ignition. I have adjusted the float several times, currently its a little above horizontal upside down, and the fuel bulb pumps up tight with out gas leaking out of the carbs. So I feel like my carbs are good. Compression is uniform, so that only leaves ignition, and the only thing I haven't replaced is the distributor and rotor and the sensor. At this time I think it has to be the sensor since the missing is on all plugs above the threshold RPM.
Two questions:
1. Do you think its anything else but the sensor?
2. If it were flooding, wouldn't I still have good spark through all RPMs even if it ran rich?
Thanks for the help. All input is appreciated greatly.
I have been trying for two years to get our old 72 Johnson running right. I pretty much gave up last year, but got back into it lately. The engine sat for 17yrs, but was in good shape with low hours when it was put away. I got it running last year with a new CDI pack, coil and rectifier. The engine starts, sometime picky when cold but once warmed up, starts right up. But when lake testing, it won't plane out, when you rev it up, it starts to miss and bogs down. I have cleaned the distributor and rotor with emery paper, and its a little pitted in a few spots, but I don't think that should matter. I have re-terminated the plug wires and they ohm out good. I have been through the carbs a half dozen times. This year has fixed jets and no adjustments. I have checked compression, all about 105-110.
Last night I decided to pull the flywheel and adjust the sensor (original 1972), I moved it from .028 to .020. When I started the engine, it fired up on the first crank, and fast idled pretty good. I opened the throttle fast start lever and at a certain high rpm, I noticed the engine began to shutter and miss. I have an induction timing light that I've used to test with and noticed that all plugs seem to fire regularly up to this rpm and then the timing light starts cutting out, and flash brightly irregularly during the miss. The motor also smokes a lot. If you ease the throttle back down below this threshold, the timing light acts normal again, on all cylinders fire and no miss. Has anyone seen this before, and do you think that I have a faulty timer base sensor? I hate to keep putting money into this old boat, but I also hat to scrap it after spending the money I've already spent.
All along I've thought the plugs looked too wet, but since there is nothing to adjust on the carbs, but the float level, I conclude that it must be ignition. I have adjusted the float several times, currently its a little above horizontal upside down, and the fuel bulb pumps up tight with out gas leaking out of the carbs. So I feel like my carbs are good. Compression is uniform, so that only leaves ignition, and the only thing I haven't replaced is the distributor and rotor and the sensor. At this time I think it has to be the sensor since the missing is on all plugs above the threshold RPM.
Two questions:
1. Do you think its anything else but the sensor?
2. If it were flooding, wouldn't I still have good spark through all RPMs even if it ran rich?
Thanks for the help. All input is appreciated greatly.