Greg of Racine
Member
At wide open throttle, about 4200 RPM, engine decelerates after about 15 seconds. Retarding throttle results in rapid, repeated backfiring. As boat came off of plane while slowing (uncommanded), re-advancing throttle resulted in normal engine accelleration and speed (3200 RPM) for pulling tubers.
Earlier performance issues were addressed with: new distributor cap, rotor, coil and plugs. Distributor and shaft were removed for rotor replacement. Ignition timing was checked and set. Subsequently, the noted top end problem showed up. All sparkplugs were found to be blackened again and were replaced again, (I have seen references to gapping plugs .035 and .045) and carburetor was replaced with remanufactured unit with electric choke upgrade. I have also seen both 140F and 160F thermostats referenced for my engine. During slow speed channel rides at less than 800 RPM, Temp gage rises to 200F. Above 800 RPM temp falls to 140F. Impeller was recently replaced in effort to correct. Marine grade fuel is being used. Approximately 500 hours on engine.
Ideas?
Earlier performance issues were addressed with: new distributor cap, rotor, coil and plugs. Distributor and shaft were removed for rotor replacement. Ignition timing was checked and set. Subsequently, the noted top end problem showed up. All sparkplugs were found to be blackened again and were replaced again, (I have seen references to gapping plugs .035 and .045) and carburetor was replaced with remanufactured unit with electric choke upgrade. I have also seen both 140F and 160F thermostats referenced for my engine. During slow speed channel rides at less than 800 RPM, Temp gage rises to 200F. Above 800 RPM temp falls to 140F. Impeller was recently replaced in effort to correct. Marine grade fuel is being used. Approximately 500 hours on engine.
Ideas?
