donfielder
Recruit
- Joined
- Jun 20, 2011
- Messages
- 4
i have a 2003 mercury 8hp that i use only a few times a year. i have always flushed the engine(salt water) after use and run the fuel out of the engine after each use. this year when i first used the engine it ran great and started easily. as i used the engine starting and stoping it seemed fine. however, when i started back to the dock on a fairly long run (1 mile) the engine ran a short distance fine and suddleny felt like it lost a cylinder. the engine was extremely down on power to the point that i felt that if i let up on the gas it would likely die. i made it back to the dock and found that it did not die but did not recover. i inspected the plugs and they looked fine. i replaced them anyway. later i took the boat back out but stayed close to the dock. it seem to run fine. the next morning i went back out and found the plugs must have helped but now the motor would still loose power but would backfire and seem to recover. i found that if the engine was cool it would run fine. when it warmed up it would start backfiring.
i took the thing home and have replaced the coils and the switch box. in a barrel it runs fine cold but when it reached operating temp is started backfiring again when i reved the engine. i removed the carb and cleaned and rebuilt it with a new fuel filter. the motor idles smoother(i thought it idled ok before but i could hear it idle smoother) the carb was clean but the fuel pump diaphram was streached out. the manual says this diaphram must be totaly flat. i then got out a timing light and checked the timing. it says at wide open in gear it should be at 36 degrees. the timing is good. i did not check the base idle timing. maybe this is part of the problem. i do not know.
i finally got the engine to stop backfiring by turning the idle screw out another full turn( 2 1/2 turns). if i turn it back in to where it should be it starts backfiring again. with it turned out to 2 1/2 it feels like the engine is running rich at higher rpms. it feels like is has a slight drag or bog at higher speed(half throttle). it is tollerable but you can tell it is not a smooth clean high speed.
i have owned this motor for several years and it has NEVER done this. i have always used the quicksilver oil 50:1 and 93 octane fuel. the motor has always and even now started very easily. many times a half pull on the rope and it is running.
i have read two other posts about this. one talked about the spark advance and carburator opening timing. maybe this is the problem i do not know. the manual does not tell you how to check the carb opening timing. i have never bothered any of the linkage adjustments.
the only thing i have done to this engine is i replaced the waterpump/housing and the main shaft(rust) i replaced these parts before i used the engine this year. maybe this has something to do with the problem. the other thing i have found is this year when i used the motor at times when it was in neutral the safety lock to prevent you from starting the motor in gear would dragging the flywheel. it would make a clicking clatter noise when i started the engine. when i took the engine home i found that i had to adjust the linkage to prevent it from dragging. why did i have to adjust this? i have never had to before. why suddenly now? the adjustment to the rod has corrected the arm from contacing the flywheel.
i have spent a small fortune on this motor with no luck. the carb looks fine. it was clean and had no corrosion. the reeds looked fine also.
i cannot be the only one with this problem. i could sure use some advice. i appreciate any help on this. i am going back to st. andrews park in panama city fl. in two weeks.
thank you,
don
i took the thing home and have replaced the coils and the switch box. in a barrel it runs fine cold but when it reached operating temp is started backfiring again when i reved the engine. i removed the carb and cleaned and rebuilt it with a new fuel filter. the motor idles smoother(i thought it idled ok before but i could hear it idle smoother) the carb was clean but the fuel pump diaphram was streached out. the manual says this diaphram must be totaly flat. i then got out a timing light and checked the timing. it says at wide open in gear it should be at 36 degrees. the timing is good. i did not check the base idle timing. maybe this is part of the problem. i do not know.
i finally got the engine to stop backfiring by turning the idle screw out another full turn( 2 1/2 turns). if i turn it back in to where it should be it starts backfiring again. with it turned out to 2 1/2 it feels like the engine is running rich at higher rpms. it feels like is has a slight drag or bog at higher speed(half throttle). it is tollerable but you can tell it is not a smooth clean high speed.
i have owned this motor for several years and it has NEVER done this. i have always used the quicksilver oil 50:1 and 93 octane fuel. the motor has always and even now started very easily. many times a half pull on the rope and it is running.
i have read two other posts about this. one talked about the spark advance and carburator opening timing. maybe this is the problem i do not know. the manual does not tell you how to check the carb opening timing. i have never bothered any of the linkage adjustments.
the only thing i have done to this engine is i replaced the waterpump/housing and the main shaft(rust) i replaced these parts before i used the engine this year. maybe this has something to do with the problem. the other thing i have found is this year when i used the motor at times when it was in neutral the safety lock to prevent you from starting the motor in gear would dragging the flywheel. it would make a clicking clatter noise when i started the engine. when i took the engine home i found that i had to adjust the linkage to prevent it from dragging. why did i have to adjust this? i have never had to before. why suddenly now? the adjustment to the rod has corrected the arm from contacing the flywheel.
i have spent a small fortune on this motor with no luck. the carb looks fine. it was clean and had no corrosion. the reeds looked fine also.
i cannot be the only one with this problem. i could sure use some advice. i appreciate any help on this. i am going back to st. andrews park in panama city fl. in two weeks.
thank you,
don