Just bought a pontoon with a 83 90 hp Johnson outboard. I've took it out 2 times since I bought it and been stranded both times. It starts and ran fine but after going down the lake a little bit it kinda sputtered a bit and died and wouldn't start back. Any ideas? Coil?
In agreement with Tim but I would add:
And now you know why that fellow wanted to sell it. Yeah, that's usually the case. However, anything can be fixed.
Saying the compression and spark is good is speaking in generalities and tells us nothing. We need to know exactly what the psi compression reading is on all "individual" cylinders. Standing in back of the engine, facing the spark plugs, the cylinders are numbered as:
2....1
4....3
Same scenario holds true on the spark... which should jump a 7/16" air gap with a strong blue lightning like flame... a real SNAP! Does it?. Note that the 7/16" air gap is important. Don't have a air gap tester handy at the moment?... you can substitute using a #2 philips screwdriver, stick the rip of the screwdriver into the coil spring that normally grips the spark plug top, then hold the shank of the screwdriver that distance away from the powerhead. That figure of 7/16" confuses some... think 1/2" for a setting in that case.
If any certain cylinder is not as it should be as described above.... explain what and as to what cylinder.
The spark plugs should be QL77JC4 Champion plugs, gaped at either ,030 (long life) or .040 (super hot spark). If your plugs are different, what are they? Also, what do your present s/plugs look like when removed... and do they all look alike? If they vary... how and what cylinder?
Standing in back of the engine, facing the spark plugs, Port is LEFT... Starboard is RIGHT. Best to use those terminologies as standing elsewhere, the location of left/right changes. You probably already are aware of that, but for those that don't....... now they do.
Now, when that engine cuts back on the rpms, loses power, slows down.... is that a gradual drop of power such as a automobile running out of gas... or is it a sudden instantaneous drop such as someone yanking a couple spark plugs wires off?
You sound like a very impatient fellow (ready to sink the craft already). Keep in mind that a boater must be a person of patience who is funded well enough to throw money at that hole in the water (hole = water displaced by the weight of the craft). If this is not the case, a second choice should not be an aircraft!