the_last_hour
Member
Motors are twin 300hp carbed 350's model year 2006. Started with difficult ignition problem and that problem is now resolved. We have a new problem after 30 hours of pro mechanic work we haven't fixed it. The symptoms are as follows...
Start the boat leave the dock, get on plane, everything works great for as long as you want to run. Both engines tach up fine, all is well with the world. Once you come off of plane, and travel at 800 rpms in gear for 10 minutes, the starboard engine will not tach up past 2500, coughs occassionally out of the carb. If you keep running it, it will eventually tach up very slowly with some surging. After 10 minute run on plane it will get past 3400 eventually, but will not keep up with the port motor. Floscans increase in gph with more throttle, but no rpm increase. If you come off of plane and back to idle speed, it will eventually stall out, but start back up easily.
Things that have been done so far... New plugs twice, swapped carbs, new fuel pump, new fuel filter, compression check good, new plug wires, new coil, new module in mallory distributor, new ignition key switch. We have not yet put psi check on fuel delivery or bypassed tach- that is next. Also - new fuel, both engines routed to same fresh tank of gas to eliminate bad gas. Any suggestions?
Start the boat leave the dock, get on plane, everything works great for as long as you want to run. Both engines tach up fine, all is well with the world. Once you come off of plane, and travel at 800 rpms in gear for 10 minutes, the starboard engine will not tach up past 2500, coughs occassionally out of the carb. If you keep running it, it will eventually tach up very slowly with some surging. After 10 minute run on plane it will get past 3400 eventually, but will not keep up with the port motor. Floscans increase in gph with more throttle, but no rpm increase. If you come off of plane and back to idle speed, it will eventually stall out, but start back up easily.
Things that have been done so far... New plugs twice, swapped carbs, new fuel pump, new fuel filter, compression check good, new plug wires, new coil, new module in mallory distributor, new ignition key switch. We have not yet put psi check on fuel delivery or bypassed tach- that is next. Also - new fuel, both engines routed to same fresh tank of gas to eliminate bad gas. Any suggestions?