Ok, here's the history first and soory for the long post, but I think it may be important. My 2002 Sea Pro 18' CC ran well thru 2007 and I always changed the impeller every 2 yrs and new plugs every year, but no other maintenance was done. I believe I fogged the engine each year and at the end of 2007. Never went out in 2008. I drained most of the gas in 2009 and added new fuel (87 octane) for the 2009 season. Boat fired right up and ran fine. Fuel sending unit went bad and I ran out of gas once in 2009. Fixed sending unit and only used a one more time in 2009 and had the same problem as in 2010 once, but ran fine for the rest of the trip. In 2010, boat fired up and ran fine, initially. On first outing in 2010 while at WOT for about 5-10 min (after running fine at idle and during trip out to the fishing grounds), engine suddenly bogged down and died. I thought I had some water in the gas because it took quite a bit of cranking to get it to start stumbling and sputtering and eventually start while manually feathering the throttle at the carbs. After a half hour of this, I got it to run enough to get into gear and could get it to pick up speed and stop sputtering by quickly moving throttle lever forward and back quickly. After finally picking up speed, it sounded fine for another 5-15 minutes of running WOT, then it bogged and shut off again. Cranked and Cranked while manually feathering the throttle linkage at the carbs to get it running again. Once started again, we made it to the dock without sputtering or stopping. Only used once in 2010. Now 2011, decided it was probably gunked up in the carbs. Bought rebuild kits for each carb and had my cousin (who is think is knowledgable about marine engines and only down my location for a day) help me clean, rebuild, and install the carbs. We found a lot of sand looking stuff in the bowls, which he said looked like corrosion. We made sure all passages and small ports were open by passing a small brass wire through them. I installed a yamaha fuel/water seperator and a clear fuel filter (pre-primer bulb) to see if anything is getting past the filter. Tried starting. No start until I used starting fluid. Got started, but spitted and sputtered. Would shut down if I didn't manually feather the throttle linkage at carbs. Sounds like it's missing, but no different than when I had those problems on the water. Except now, it doesn't start running fine after a bid of feathering the throttle. Pulled the carbs again and used thin brass wire to check all passages, all good and no more sand or gunk in bowls. I also cleaned the fuel enrichment device, which had some of the same sandy gunk stuck behind the plastic housing behind the diaphragm (not a complete closing at all, but it was there). I also replaced the diaphragm and gasket in the front of the fuel pump just for good measure, even though everything looked good. I pulled the inline fuel filter and had sandy gunk on the screen, so cleaned it too. All fuel lines look good. Put everything back together today. Engine started after a bit without the need for starting fluid, but still sounded like it was missing. I used a spray engine restorer, spraying into carbs until almost entire can was used (as directed on can and smoked up the joint). Can states it removes gunk from piston, valves, etc and restores engine power. Waited the directed 30 min and restarted to run it out. Engine ran and once major smoking stopped, it was still sounding like a miss. Fairly regular, but also had some sputters added in here and there. I'm stumped. It happens at idle and causes a stall, but it also happens when I add a little manual throttle (no more than 1500 rpm, since I'm only using muffs for water source. What do you think is wrong? electric (it has CDI with Micro computer control? I was told by another mechanic that this engine 2002 90 TLRA does not require timing and synch unless you mess with the linkage or screws, which I have not. HELP! My next thought is to send to a professional. I don't have a compression guage. Anything else I should try before spending the big bucks? Again, sorry for the long post.
Steve