my 2002 OX66 250 port engine has a micro flutter and cuts outs at WOT...they are so short and quick that the TACH dosen't drop but you feel it. Rough idle followed. Now I cold start the engine and it starts at 600 rpms, jumps to 1400, then down to 400, back up back down then stalls. My engines have 1550 hrs well cared for..non ethanol boat just had full tune up 50 hrs..but 22 months ago...not using it like I used too. Starboard engine runs fine. Fresh 200gal gas, I run ring free every other fill..have a pint and half in tank now...not enough to shock the engines. O2 sensor and joint is clean..it's always been pretty clean because of the ring free. No water in fuel system.
Good news-bad news. I changed spark plugs...as mentioned old ones were 50hrs but looked carbed..I installed BR9Hs-10 NGK plugs-same as always and the boat ran like a dream..perfect idle start..went 1300..settled to 600 as it should and very, very smooth. Bad news-Running great but the flutter came back after only 20 minutes WOT. Back at the dock as soon as it went into idle the rpms dropped to 400 and stalled. Next day I did cold start and all the same problems back again.
Second round-Thermostats new, Change VST filter-old was clean, changed all three LP pumps and TPS. Same problems. Cold start at 600..jumps arounds then stalls...at all other speeds except for the WOT flutter ...it seems to run perfect. Any ideas? Temp sensor maybe?..but why the flutter....are the problems related or seperate? My guess is a lack of fuel WOT and at idle..but I dont know. Batteries are strong. BTW- I can swap parts from my Starboard engine that runs fine if you have ideas...limited of course. Hey, is it possible to foul plugs in 25 minutes or was that a fluke that the new plugs seem to correct the problem only a half hour?
Good news-bad news. I changed spark plugs...as mentioned old ones were 50hrs but looked carbed..I installed BR9Hs-10 NGK plugs-same as always and the boat ran like a dream..perfect idle start..went 1300..settled to 600 as it should and very, very smooth. Bad news-Running great but the flutter came back after only 20 minutes WOT. Back at the dock as soon as it went into idle the rpms dropped to 400 and stalled. Next day I did cold start and all the same problems back again.
Second round-Thermostats new, Change VST filter-old was clean, changed all three LP pumps and TPS. Same problems. Cold start at 600..jumps arounds then stalls...at all other speeds except for the WOT flutter ...it seems to run perfect. Any ideas? Temp sensor maybe?..but why the flutter....are the problems related or seperate? My guess is a lack of fuel WOT and at idle..but I dont know. Batteries are strong. BTW- I can swap parts from my Starboard engine that runs fine if you have ideas...limited of course. Hey, is it possible to foul plugs in 25 minutes or was that a fluke that the new plugs seem to correct the problem only a half hour?
