kstrayhorn
Well-known member
I've got a '73 Evinrude 9.5 Sportwin that I've been working on for a friend because I'm apparently the most mechanically inclined person he knows. It's a recent purchase for him, so I never saw it run, but according to him it ran rough and didn't want to idle (in retrospect he says he thinks "rough" was only running on one cylinder). In any case, the last time he took it out it wouldn't start at all, so he took it to a shop for diagnosis. They told him it needed a carb rebuild, new fuel pump, and new points & condensers. So I did all that for him along with a new stop button (wires were old and the jackets were completely gone), new fuel line fitting (old one was cracked, affecting fuel pressure), and new spark plugs. After all of this work, still nothing, and it's not even trying to turn over.
Here's everything I've adjusted, tried, and figured out on it:
Set, checked, and rechecked points at .020".
Gapped and regapped plugs at .030" and I've even tried overgapping the plugs to try to get a hotter spark.
Compression seems to be low, but acceptable at around 65psi in each cylinder (maybe just under, but my gauge is from the 60s and difficult to read while cranking).
Both plugs are getting spark outside of the cylinders, although one appears to have stronger spark than the other.
Tried every adjustment on the rich/lean needle from seated to 2.5 turns out.
Fuel is for sure getting to the bowl and to the cylinders, and fuel pressure is holding.
The 2 things that concern me as potential sources for the problem are:
1) When I crank it with no plugs in the cylinders, a nice mist of fuel comes out of the bottom plug hole, but nothing out of the top. Even when holding a finger or hand over the top hole, it doesn't even get wet. However, the reed valves seem to be clear and if I crank it with the plugs in, then pull them to inspect, both cylinders seem to be wet. I could be wrong, but my explanation for this is that fuel demand runs on an as needed basis as controlled by cylinder pressure. In other words, under compression and with ignition, pressure in both cylinders will draw fuel in, but without compression, there is not enough pressure to draw fuel into the top cylinder.
2) As I mentioned, one plug seems to have a stronger spark outside of the cylinder, even when switching the plugs to opposite leads. While I can't test the spark under compression, I believe this is the most likely source of the problem. After inspecting the coils, both have cracks, but one is more severely cracked than the other. Perhaps it is coincidence, but the most damaged coil coincides with the top cylinder, which had the noticeably weaker spark. However, both coils test good (~3600 ohms) across both the primary and secondary windings. My thoughts are that one or both coils is/are arcing off the flywheel under compression, weakening the spark and not allowing ignition.
So, my questions and where I need help:
Is my hypothesis concerning bad coils and arcing off the flywheel a sound one although there is spark outside the cylinders, there is no clear evidence of arcing, and the coils test good?
Is there any way I can further test the coils to confirm that this could be the problem? (I didn't want to buy a spark tester as the cost of one is almost that of a new coil).
Is there anything else I can do or test to see if the problem is somewhere else?
Is there enough evidence here to tell him to put new coils on it, or should I send him back to the shop before telling him to spend more money?
If I can get y'all any more info on it, please let me know. I look forward to any thoughts/responses and, as always, I thank you all for any input or help.
Here's everything I've adjusted, tried, and figured out on it:
Set, checked, and rechecked points at .020".
Gapped and regapped plugs at .030" and I've even tried overgapping the plugs to try to get a hotter spark.
Compression seems to be low, but acceptable at around 65psi in each cylinder (maybe just under, but my gauge is from the 60s and difficult to read while cranking).
Both plugs are getting spark outside of the cylinders, although one appears to have stronger spark than the other.
Tried every adjustment on the rich/lean needle from seated to 2.5 turns out.
Fuel is for sure getting to the bowl and to the cylinders, and fuel pressure is holding.
The 2 things that concern me as potential sources for the problem are:
1) When I crank it with no plugs in the cylinders, a nice mist of fuel comes out of the bottom plug hole, but nothing out of the top. Even when holding a finger or hand over the top hole, it doesn't even get wet. However, the reed valves seem to be clear and if I crank it with the plugs in, then pull them to inspect, both cylinders seem to be wet. I could be wrong, but my explanation for this is that fuel demand runs on an as needed basis as controlled by cylinder pressure. In other words, under compression and with ignition, pressure in both cylinders will draw fuel in, but without compression, there is not enough pressure to draw fuel into the top cylinder.
2) As I mentioned, one plug seems to have a stronger spark outside of the cylinder, even when switching the plugs to opposite leads. While I can't test the spark under compression, I believe this is the most likely source of the problem. After inspecting the coils, both have cracks, but one is more severely cracked than the other. Perhaps it is coincidence, but the most damaged coil coincides with the top cylinder, which had the noticeably weaker spark. However, both coils test good (~3600 ohms) across both the primary and secondary windings. My thoughts are that one or both coils is/are arcing off the flywheel under compression, weakening the spark and not allowing ignition.
So, my questions and where I need help:
Is my hypothesis concerning bad coils and arcing off the flywheel a sound one although there is spark outside the cylinders, there is no clear evidence of arcing, and the coils test good?
Is there any way I can further test the coils to confirm that this could be the problem? (I didn't want to buy a spark tester as the cost of one is almost that of a new coil).
Is there anything else I can do or test to see if the problem is somewhere else?
Is there enough evidence here to tell him to put new coils on it, or should I send him back to the shop before telling him to spend more money?
If I can get y'all any more info on it, please let me know. I look forward to any thoughts/responses and, as always, I thank you all for any input or help.