Mark Stochl
Recruit
- Joined
- Jun 30, 2002
- Messages
- 1
I have a 1997 Yamaha 200 Saltwater series on a 20ft. Grady White. While underway (~4200 rpms), especially in calm to moderate sea conditions, my motor runs very well (smooth). But in heavy sea conditions with lots of heavy pounding, now and then the motor will all of a sudden develop a "skip" or "stumble". When the motor starts running rough like this, the rpms on the tachometer begins to fluctuate up and down (surging) and acts as though a cylinder is cutting out. It is almost like water in the fuel, dirty carburator (fouled jet?) or possibly a faulty power pack/coil (like one of my previous 1986 Evinrude 175). When I idle down to neutral for a minute or so, the problem will usually tend to clear itself until the boat takes another big pound. If I continue operating the motor at high speed (4200 rpms) after this develops, it will usually continue although has all of a sudden cleared (like running on all six cylinders again) up as soon as sea conditions subsided. When it is hesitating, if I push in my key to choke/prime, it seems to momentarily help smooth it out. The next day, if it is calmer, the engine runs fine again. Also, I have noticed that at idle, the engine will sometimes develop a "cough" and "sneeze" and want to quit on me. I have replaced the plugs and they all appear to look the same (one/more cylinders do not appear to be running too lean/rich). There is no detectable water in the fuel system (I have changed out the fuel filter/water seperator and have even run carburator cleaner through it several times). Could a piece of dirt in the carburator be intermittently plugging the high speed jet or is this too unlikely? I would think a piece of dirt would stay lodged regardless. Should I consider having the carburators rebuilt? How likely is it that there is some ignition problem (only happens in rough seas) and how do I diagnose it? Help! 