Re: Merc 250 running rich
Some additional information: The motors are identical except for one being counter-rotation. The TPS has both been changed and adjusted. When turned to the lower numbers, the motor seem to run richer if possible. Compression is good, and the motors run great when the throttle is opened. When first started or right after a run, they do not smoke. Then, as they continue to idle, the smoke begins to show up as they begin to run richer and richer.<br />The poppet valve has been changed, along with almost all sensors. If you do any trolling, or idling, the plugs will load up to the point you cannot get them to keep running when you shift into gear. If you ever do, they will run great if you ease forward on the throttles. All you have to do is change the plugs, and you are good to go until you idle for a few minutes again.<br />I went with a one range hotter plug, (NGK) and it helped a little. Everything is in specs. They just will not run right.<br />I bought this boat second hand,and I suspect that this might be the reason it was sold, as the boat itself is great.<br />According to Mercury, both power head were changed under warranty when the motors were brand new because of the same problem: Cracked ring and/or damaged piston of the number 5 cylinder. No idea why or how this happened to both motors at the same time.<br />The problem could possibly date from that time, I just don't know.<br />At the present time, I have ordered a new set of the bleeder/check valves for both motors. There are so many of them, and they are so hard to get to, I do not want to waste time pulling them off and checking them. Contrary to how it sounds, I have had two excellent factory trained techs working on them and we have not been just shotgunning the problem by throwing parts at it. But I am to the point I would do that if I knew of any parts to throw<G>.<br />What really blows my mind, is that both motors have the exact same problem, and the only thing they share is the gas tank. Which has been checked and we have run one off the shop tank.<br />When we first pulled the intake/butterfly assembly off, we figured it might have clogged injectors. However they spray fine. Is there any possibility that someone could have sent them off to be cleaned or repaired and got some back that flow more then stock?<br />There are a lot of places that will swap injectors for you fairly cheap, and I wonder if that has been done.<br /><br /> Thanks
