I just purchased a 89 Yamaha 225 to replace a 200 Mercury for my boat. The engine was installed and rigged by authorized dealer. When I open throttle to full, the engine revs up to WOT, but after only a couple of seconds, it starts bogging down to about 3500 - 4000 rpm. Dealer has checked fuel lines, pumps, plugs and thinks it might be the computer. Anyone else had any experience like this?
You've got a bad fuel pump. The Yamaha V6's have dual pumps and if one goes bad, its does just what you describe. The second pump won't carry enough fuel to run the engine past 3000 rpms. If you slow down, the single pump will refill the carbs and you can run normally until the carbs run low again. Buy two kits and rebuild both.
Make sure you have the proper size fuel line for your outboard, you might have one too small...too long or clogged. Are you running a water seperator....could be plugged up too.
Ive seen a few problems on the 150- 200 yamis around that year with the same type of problem. Rebuilt the carbs two even three times. No good. Wound up replacing carb bowls cuz there was blockage under the seat(fuel inlet). Motors ran beautifully! p.s. seats are not removeable