I have a 1973 50HP 2 cyl Evinrude.
Brief history:
Motor has been in the family since new.
Had a piston fail last summer which blew a hole through the side of the block. Despite the repeated advice to drop it off the back of the boat I decided to rebuild. I found a used block with a good piston and decent cylinder walls which I honed. I replaced rings, many bearings, all seals, gaskets, etc. To my delite the engine started up in the spring, had good compression in both cylinders, and ran well (better than I can ever remember) up until last week.
I took it out after sitting for about three weeks and within 5 minutes the bottom cylinder began misfiring. This grew steadily worse until it I could feel the second cylinder kick-in only every now and again.
Brought it home to check things out. Good spark but low compression in the bottom cylinder. (I dont have a compression tester but it is obvious by turning the flywheel) It starts and runs ok in the test tank and both cylinders fire.
Took it back out on the water with the same results except this time I noticed that at full throttle the engine will cycle from 2 cylinders firing to 1 firing every 10 seconds or so. At very low speed I can get both to fire with only an occasional misfire which tells me there is a fuel flow problem. The fuel pump is driven off the bottom cylinder and my thought is that if I fix the compression problem the fuel flow problem may correct itself.
So the real question is why would I suddenly loose compression in an engine with only about 10 hr after rebuild? Could the rings be stuck?
Thanks for the advice.
(Sorry for the long story)
Brief history:
Motor has been in the family since new.
Had a piston fail last summer which blew a hole through the side of the block. Despite the repeated advice to drop it off the back of the boat I decided to rebuild. I found a used block with a good piston and decent cylinder walls which I honed. I replaced rings, many bearings, all seals, gaskets, etc. To my delite the engine started up in the spring, had good compression in both cylinders, and ran well (better than I can ever remember) up until last week.
I took it out after sitting for about three weeks and within 5 minutes the bottom cylinder began misfiring. This grew steadily worse until it I could feel the second cylinder kick-in only every now and again.
Brought it home to check things out. Good spark but low compression in the bottom cylinder. (I dont have a compression tester but it is obvious by turning the flywheel) It starts and runs ok in the test tank and both cylinders fire.
Took it back out on the water with the same results except this time I noticed that at full throttle the engine will cycle from 2 cylinders firing to 1 firing every 10 seconds or so. At very low speed I can get both to fire with only an occasional misfire which tells me there is a fuel flow problem. The fuel pump is driven off the bottom cylinder and my thought is that if I fix the compression problem the fuel flow problem may correct itself.
So the real question is why would I suddenly loose compression in an engine with only about 10 hr after rebuild? Could the rings be stuck?
Thanks for the advice.
(Sorry for the long story)