I have a 2000 Yamaha 150 SWSII OX66 SX150txry.
If a cylinder was cutting out at speed what kind of RPM drop would i see? I've been trying to chase down a lack of WOT throttle RPM all season. Boats been running well under normal use. I checked the plugs the other day and one plug was real clean, like its not firing all the time. Plugs were originally replaced back in May. Changed the plugs again and the boat ran great. Picked up top speed and RPM. After running the boat for a half hour, the boat started to surge at cruise speed. Would drop a 100 rpm or so. Seemed to be less noticable at lower RPMs under 3600, but did notice it on the holeshot. Fuel system had been gone through at the beginning of the season, all filters were replaced or inspected including VST,regulator screen, injector screens. Low pressure pumps replaced, 02 replaced, spark plug caps replaced. Compression check 115-120 all cylinders (previous owners definition on routine maintenace differed from the shop manuals). Pumping the primer ball did not change performance. It seems like a cylinder is cutting out. Im thinking its something ignition related because the new plug seemed to improve things temprorarily. Are coils common failures on these engines? I'm gonna start checking it out this week but would like the problem resolved before I pull the boat for the winter. Any info is much appreciated.
Thanks
Mike
If a cylinder was cutting out at speed what kind of RPM drop would i see? I've been trying to chase down a lack of WOT throttle RPM all season. Boats been running well under normal use. I checked the plugs the other day and one plug was real clean, like its not firing all the time. Plugs were originally replaced back in May. Changed the plugs again and the boat ran great. Picked up top speed and RPM. After running the boat for a half hour, the boat started to surge at cruise speed. Would drop a 100 rpm or so. Seemed to be less noticable at lower RPMs under 3600, but did notice it on the holeshot. Fuel system had been gone through at the beginning of the season, all filters were replaced or inspected including VST,regulator screen, injector screens. Low pressure pumps replaced, 02 replaced, spark plug caps replaced. Compression check 115-120 all cylinders (previous owners definition on routine maintenace differed from the shop manuals). Pumping the primer ball did not change performance. It seems like a cylinder is cutting out. Im thinking its something ignition related because the new plug seemed to improve things temprorarily. Are coils common failures on these engines? I'm gonna start checking it out this week but would like the problem resolved before I pull the boat for the winter. Any info is much appreciated.
Thanks
Mike
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