I have a 1959 Evinrude Lark that I have been running on an old cedarstrip for many years. Last summer, I refurbished it -- paint, wires, fuel lines, the coil mounting plate (used, but little play), plugs, points, condensers, impeller, thermostat, overspeed vacuum switch (used but good condition), etc. etc. I even added a ground wire from the coil mounting plate to the block. (I was experimenting with some electronic ignition modules, but left the ground wire when I went back to points). I added a belt-driven generator from a later 40hp, lightly machining the flywheel to accept the press-fit cogged drive because the 40hp flywheel is bored to fit a larger crank. All was good in the world when it was done, but the season was just about over.
This year, I have been having problems with stalling at idle when it gets warmed up. It would run at speed without any issue, but coming down to low speeds (or after an extended period of slow operation) it wants to stall at any throttle setting less than the shift lock-out.
I initially thought it must be fuel related, tried fiddling with the mixture screws, changed fuel line o-rings, etc. but the glass bowl under the fuel pump is full. I checked the compression and both cylinders are over 100psi, within a few PSI of each other (the actual compression may be a higher, I have an automotive gauge with a hose, which tend to be inaccurate on small motors) I eventually connected a set of neon spark checkers in-line and have determined that the spark quits on both cylinders when it stalls. No spark at all until it cools down.
I swapped in new OMC brand points and condensers with no change -- it starts and runs when cold (with choke). At the point where choke is no longer required (about the time steam starts mixing with the spray of water out the exhaust) it continues to putt at minimum throttle. As it continues to warm up, it needs more and more throttle to keep running. Spark becomes intermittent otherwise. Today I installed brand-new OMC brand coils (the old ones were aftermarket, I can't quite make out the brand, but they were green and "made in Germany") I also compared the magnet to a flywheel from a later 40 hp. Using a digital handheld scale and a small chunk of steel, the 40 hp flywheel required ~5.5 lbs of pull to remove the steel, my 35 hp flywheel released the steel at about 4.5 lbs. It grabs a screwdriver dangling between two fingers from about an inch away.
If anything, the motor now is worse -- it started kicking (misfiring?) at anything less than full throttle and died, leaving me stuck in the middle of the lake, when I throttled back slightly. I noticed that the flywheel was quite warm to the touch. So was the generator -- warmer than the starter motor, anyway.
After sitting 1/2 an hour or so, it restarted, but again, the misfiring began again after a few minutes on the run home, even running with the hood off for extra air flow. Now it won't restart, but it's dark and I haven't investigated to see if I have spark or not. I don't really think the motor is overheating -- it pulls over fine after it stalls, it still spits water out the exhaust when it's running, the paint is not discoloured -- but this motor is too old and doesn't have the temperature sensor of the later versions.
Any thoughts on what to try next? I'm at my wit's end with this thing now. I have a good early-60's 40hp Johnson I can throw on there, but I really like the "Golden Jubilee Edition" Lark on that boat.
This year, I have been having problems with stalling at idle when it gets warmed up. It would run at speed without any issue, but coming down to low speeds (or after an extended period of slow operation) it wants to stall at any throttle setting less than the shift lock-out.
I initially thought it must be fuel related, tried fiddling with the mixture screws, changed fuel line o-rings, etc. but the glass bowl under the fuel pump is full. I checked the compression and both cylinders are over 100psi, within a few PSI of each other (the actual compression may be a higher, I have an automotive gauge with a hose, which tend to be inaccurate on small motors) I eventually connected a set of neon spark checkers in-line and have determined that the spark quits on both cylinders when it stalls. No spark at all until it cools down.
I swapped in new OMC brand points and condensers with no change -- it starts and runs when cold (with choke). At the point where choke is no longer required (about the time steam starts mixing with the spray of water out the exhaust) it continues to putt at minimum throttle. As it continues to warm up, it needs more and more throttle to keep running. Spark becomes intermittent otherwise. Today I installed brand-new OMC brand coils (the old ones were aftermarket, I can't quite make out the brand, but they were green and "made in Germany") I also compared the magnet to a flywheel from a later 40 hp. Using a digital handheld scale and a small chunk of steel, the 40 hp flywheel required ~5.5 lbs of pull to remove the steel, my 35 hp flywheel released the steel at about 4.5 lbs. It grabs a screwdriver dangling between two fingers from about an inch away.
If anything, the motor now is worse -- it started kicking (misfiring?) at anything less than full throttle and died, leaving me stuck in the middle of the lake, when I throttled back slightly. I noticed that the flywheel was quite warm to the touch. So was the generator -- warmer than the starter motor, anyway.
After sitting 1/2 an hour or so, it restarted, but again, the misfiring began again after a few minutes on the run home, even running with the hood off for extra air flow. Now it won't restart, but it's dark and I haven't investigated to see if I have spark or not. I don't really think the motor is overheating -- it pulls over fine after it stalls, it still spits water out the exhaust when it's running, the paint is not discoloured -- but this motor is too old and doesn't have the temperature sensor of the later versions.
Any thoughts on what to try next? I'm at my wit's end with this thing now. I have a good early-60's 40hp Johnson I can throw on there, but I really like the "Golden Jubilee Edition" Lark on that boat.
