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Hi I'm new to this forum, hopefully you guys will have some ideas. I have a 1985 twin 260hp twin inboard boat. Port motor is counter rotating both motors are running Thunderbolt IV ignitions. The boat is new to me.....I purchased with a blown starboard motor, which has been replaced and running great. The port motor, however has a strange thing going on. It starts and idles great and will get up on plane 3000-3500rpm indefinitely. After running for 20-30 minutes or so on plane, if I back off the throttles the port motor dives down to 1200 rpm abruptly and then won't accelerate back up on plane. If you let it sit for an hr or so, it resumes normal operation. I'm fairly certain it's not a fuel issue, as it was running without any issue at higher rpms. I suspect ignition? Perhaps the Thunderbolt module is not advancing when it gets hot? Any thoughts?
Paul
Paul
