1972 Steury V518.
So this engine was tuned up last year and this year has started backfiring after WOT for 5 minutes or so. Engine pushes boat at around 33 mph then slows down a few mph then backfires once or twice while at full throttle. I back off the throttle and it continues to backfire more frequently. Idle speed-no backfire. I can get back WOT after several minutes of idle speed.
Note that Sunday after trolling at idle for a couple of hours, then going WOT, boat ran great for 8-10 minutes-no backfire. Then after sitting and fishing and going WOT, backfire started again at the 5 minute mark.
I have no idea how hot this motor is running-gotta fix the gauge. It is pumping water while running(we have inserted a garden hose connect at the engine which when uncapped pumps a lot of hot water out).
Engine starts and idles beautifully.
Newer plugs, wires, distributor cap, thermostat.
Used lead additive last year-no issues with backfire. Fresh fuel, using lower octane without lead additive this year. Did use the last of additive once this year-did not stop backfiring. Tank has been filled 3 times this year, so no old gas.
Thank you to all who helped me rescue this boat. Put a "new" outdrive on last year and (fingers crossed) it will continue to live on.
So this engine was tuned up last year and this year has started backfiring after WOT for 5 minutes or so. Engine pushes boat at around 33 mph then slows down a few mph then backfires once or twice while at full throttle. I back off the throttle and it continues to backfire more frequently. Idle speed-no backfire. I can get back WOT after several minutes of idle speed.
Note that Sunday after trolling at idle for a couple of hours, then going WOT, boat ran great for 8-10 minutes-no backfire. Then after sitting and fishing and going WOT, backfire started again at the 5 minute mark.
I have no idea how hot this motor is running-gotta fix the gauge. It is pumping water while running(we have inserted a garden hose connect at the engine which when uncapped pumps a lot of hot water out).
Engine starts and idles beautifully.
Newer plugs, wires, distributor cap, thermostat.
Used lead additive last year-no issues with backfire. Fresh fuel, using lower octane without lead additive this year. Did use the last of additive once this year-did not stop backfiring. Tank has been filled 3 times this year, so no old gas.
Thank you to all who helped me rescue this boat. Put a "new" outdrive on last year and (fingers crossed) it will continue to live on.
