Okay, let?s try this again.
Thanks to all who responded before, but I?m not a complete idiot. I know, that?s a pretty big leap of faith on a discussion board, but let?s start out with more facts.
Let?s assume that I?m comfortable taking apart a four cycle automobile or aircraft engine, putting it back together, and it works. Let?s also assume I have the manuals for this particular engine, but do not have any two-cycle experience. Let?s ALSO assume I do own and read the manual, so I?m not running the water-cooled engine without a water supply.
Engine: 1959 Evinrude 50 hp V-4 two cycle.
Engine sat for a few years after the previous owner had problems. Then I got it.
What I?ve done to it-
Carb rebuild (float was saturated with fuel, no longer floated. Otherwise, in pretty good shape)
Fuel pump rebuild (no holes, but plastic piece was a little stiff)
Reset linkages to factory specs
Gapped magneto points
Replaced lower unit oil
Changed spark plugs, plugs now run fairly black with white to chocolate brown tips (slightly rich/oil fouled due to two cycle?)
Compression (cold) 85-90 psi, all 4 cylinders
Running engine on 25:1 gas-oil mix, as per manual. Using fresh gasoline and oil, bought within 1 week of running.
After carb and fuel pump rebuild, the engine started easily. I ran the engine without the cover on and it produced good power, but would occasionally cough and sputter. Discovered water was splashing on the magneto, and into the vent hole, causing some electrical issues. Covered the mag with a plastic bag, and the engine ran pretty well for 20 minutes.
Next time out on a lake a week later, the engine would not run more than about 2-3 minutes before it would cough, sputter, and die. Engine would lose power rather suddenly, possibly knocking, then die. Brought it back into shore, ran it (yes, in a test tank) and had the same problem. Engine seemed to konk out right about the same time the thermostat was about to kick in. Engine exhaust had water droplets and steam coming out before that point, as per the manual. Immediately after the engine died, the thermostat kicked in and the ?spurt? of water (as per the manual) came out the exhaust.
After waiting a minute, would try starting the engine again, and would start no problem. Ran it 2-3 minutes, had the same problem. Repeat several times.
It?s not a fuel vent issue (tank vented), not a fuel contamination issue (swapped tanks with different fuel), not an electrical issue (happens too predictably), not a carb jetting issue (happens at any throttle setting), not a fuel supply issue (no bubbles in fuel line, carb filter bowl always full, carb fuel strainer new with rebuild and checked as clear).
Bottom right cylinder was significantly warmer than the rest of the engine. In a V-4 as this is set up, it doesn?t seem like it would be a carburetor issue, otherwise it would affect BOTH cylinders on that bank. I?m thinking it might be a valve issue (bad reed valves). After 50 years worth of corrosion, heating and cooling, and millions of flex cycles, I?m guessing some carbon buildup or metal fatigue could weaken the valves or not seal them properly, and not leave them as efficient as new. I am looking for a way to check them.
When I use a water supply clamp to feed water to the engine while not running, the water flows directly from the vent in the side out the bottom exhaust. Only if I close the bottom exhaust with my hand will water get to the thermostat housing.
Since the problem happens RIGHT AS the thermostat is ready to kick in, what changes so much that could cause an engine to sputter and die? Fresh, cool water in the jackets has time to come in, lowering the water temp. Since the water pumps on these things seem to have an ugly reputation on this board, I?m looking for a way to check the water pump is supplying ENOUGH water. If the rubber impellers are cracked or broken, it might supply SOME water, but not enough to cool it at full speed. If I disconnect the cylinder supply hoses from the thermostat housing and crank it over with the starter, how much water should I see?
My next step (if the water pump appears to be pumping water) is to remove the thermostat and see how it runs.
Any other ideas?
Thanks to all who responded before, but I?m not a complete idiot. I know, that?s a pretty big leap of faith on a discussion board, but let?s start out with more facts.
Let?s assume that I?m comfortable taking apart a four cycle automobile or aircraft engine, putting it back together, and it works. Let?s also assume I have the manuals for this particular engine, but do not have any two-cycle experience. Let?s ALSO assume I do own and read the manual, so I?m not running the water-cooled engine without a water supply.
Engine: 1959 Evinrude 50 hp V-4 two cycle.
Engine sat for a few years after the previous owner had problems. Then I got it.
What I?ve done to it-
Carb rebuild (float was saturated with fuel, no longer floated. Otherwise, in pretty good shape)
Fuel pump rebuild (no holes, but plastic piece was a little stiff)
Reset linkages to factory specs
Gapped magneto points
Replaced lower unit oil
Changed spark plugs, plugs now run fairly black with white to chocolate brown tips (slightly rich/oil fouled due to two cycle?)
Compression (cold) 85-90 psi, all 4 cylinders
Running engine on 25:1 gas-oil mix, as per manual. Using fresh gasoline and oil, bought within 1 week of running.
After carb and fuel pump rebuild, the engine started easily. I ran the engine without the cover on and it produced good power, but would occasionally cough and sputter. Discovered water was splashing on the magneto, and into the vent hole, causing some electrical issues. Covered the mag with a plastic bag, and the engine ran pretty well for 20 minutes.
Next time out on a lake a week later, the engine would not run more than about 2-3 minutes before it would cough, sputter, and die. Engine would lose power rather suddenly, possibly knocking, then die. Brought it back into shore, ran it (yes, in a test tank) and had the same problem. Engine seemed to konk out right about the same time the thermostat was about to kick in. Engine exhaust had water droplets and steam coming out before that point, as per the manual. Immediately after the engine died, the thermostat kicked in and the ?spurt? of water (as per the manual) came out the exhaust.
After waiting a minute, would try starting the engine again, and would start no problem. Ran it 2-3 minutes, had the same problem. Repeat several times.
It?s not a fuel vent issue (tank vented), not a fuel contamination issue (swapped tanks with different fuel), not an electrical issue (happens too predictably), not a carb jetting issue (happens at any throttle setting), not a fuel supply issue (no bubbles in fuel line, carb filter bowl always full, carb fuel strainer new with rebuild and checked as clear).
Bottom right cylinder was significantly warmer than the rest of the engine. In a V-4 as this is set up, it doesn?t seem like it would be a carburetor issue, otherwise it would affect BOTH cylinders on that bank. I?m thinking it might be a valve issue (bad reed valves). After 50 years worth of corrosion, heating and cooling, and millions of flex cycles, I?m guessing some carbon buildup or metal fatigue could weaken the valves or not seal them properly, and not leave them as efficient as new. I am looking for a way to check them.
When I use a water supply clamp to feed water to the engine while not running, the water flows directly from the vent in the side out the bottom exhaust. Only if I close the bottom exhaust with my hand will water get to the thermostat housing.
Since the problem happens RIGHT AS the thermostat is ready to kick in, what changes so much that could cause an engine to sputter and die? Fresh, cool water in the jackets has time to come in, lowering the water temp. Since the water pumps on these things seem to have an ugly reputation on this board, I?m looking for a way to check the water pump is supplying ENOUGH water. If the rubber impellers are cracked or broken, it might supply SOME water, but not enough to cool it at full speed. If I disconnect the cylinder supply hoses from the thermostat housing and crank it over with the starter, how much water should I see?
My next step (if the water pump appears to be pumping water) is to remove the thermostat and see how it runs.
Any other ideas?
