I have a 99 Mercury XR6 150hp that is giving me fits on engine start/idle. It seems to have an intermittent problem with running smoothly when the throttle is in the neutral position. I say intermittent because two weeks ago I took the boat out, it started right up and ran smooth as silk on the water.
Here's the problem. Before taking the boat out today I decided to start the engine on the muffs. The engine cranked strong, but would not start with throttle straight up. I had to advance the throttle well forward to get the engine to catch and start. After warming up a bit, I tired to pull the throttle back to neutral. As soon as the RPM slowed below about 1000 RPM the engine started running rough and appeared to have a misfire (small belches of smoke out of prop as well). If the throttle was pulled all the way to neutral the engine would die. The only way to keep it running was to keep the throttle forward and keep RPMs at about 1000. I tried moving the fule line to a fresh gas container and had the same problem. Engine seems to run find as long as the throttle is pushed up.
About three weeks ago I had similar problems and I wen t through the electrical system as per the shop manual and did not detect any issues. This included voltage checks and spark checks and anything else I had easy access to. I also checked compression and all cylinders appeared strong and consistent. I also decided to change the primer bulb and low and behold, that was when the engine began behaving properly and I took it out on the lake as indicated above.
Seems to me I am having a fuel/air issue of some kind.
Any thoughts on where to start the search? I have tried looking through the engine manual to figure out where to focus, but I am coming up blank. I'm thinking maybe a fuel pump issue or - maybe obviously - a carb problem.
Any help would be appreciated. It has already been appreciated before when I have looked through the site to solve other boat issues.
Thanks in advance
Rob
Here's the problem. Before taking the boat out today I decided to start the engine on the muffs. The engine cranked strong, but would not start with throttle straight up. I had to advance the throttle well forward to get the engine to catch and start. After warming up a bit, I tired to pull the throttle back to neutral. As soon as the RPM slowed below about 1000 RPM the engine started running rough and appeared to have a misfire (small belches of smoke out of prop as well). If the throttle was pulled all the way to neutral the engine would die. The only way to keep it running was to keep the throttle forward and keep RPMs at about 1000. I tried moving the fule line to a fresh gas container and had the same problem. Engine seems to run find as long as the throttle is pushed up.
About three weeks ago I had similar problems and I wen t through the electrical system as per the shop manual and did not detect any issues. This included voltage checks and spark checks and anything else I had easy access to. I also checked compression and all cylinders appeared strong and consistent. I also decided to change the primer bulb and low and behold, that was when the engine began behaving properly and I took it out on the lake as indicated above.
Seems to me I am having a fuel/air issue of some kind.
Any thoughts on where to start the search? I have tried looking through the engine manual to figure out where to focus, but I am coming up blank. I'm thinking maybe a fuel pump issue or - maybe obviously - a carb problem.
Any help would be appreciated. It has already been appreciated before when I have looked through the site to solve other boat issues.
Thanks in advance
Rob