1997 75 HP Merc Loading Up?

[starflt1701]

Please help, as I've had this problem off and on ever since I've owned this boat. Frequently, when I try to plane off, the engine will shake and rumble for a few seconds before smoothing out and taking off. This is especially true when the engine is not quite warmed up, or when I've been idling for a few minutes, but will sometimes happen when warm too. This is a pain when pulling a skiier. A mechanic told me the engine is running too rich and to close down the 3 idle mixture screws on the carbs. I've done that to the point where the engine wouldn't start, and then opened them up again so it would. I change the spark plugs at the beginning of every season, and the old ones are lightly tan in color, and not very wet at all. In fact, they hardly look used! By the way, after all the rumbling and shaking stops, the engine runs fine and gets to WOT with no problem. Can anyone tell me what I'm doing wrong?

 

[seldont]

Re: 1997 75 HP Merc Loading Up?

I may be wrong on this but my brother has a 1995 75 hp Merc. On his we turned the mixture screw on the number one (top) carb in til it was only 1/2 turn out. It solved his idle and take off problems. I think and again could be wrong that these motors idle on 2 cylinders then pick up the third when throttle is applied???

 

[starflt1701]

Re: 1997 75 HP Merc Loading Up?

Really? That's interesting. Do you know how many turns the other 2 carbs are backed out?