Re: Rough running 125 merc. Timing Problem?
Welcome to iboats.
<br /><br />There's probably nothing wrong. The motor will idle on the upper two cylinders, then kick in the other two above 1/3 throttle. Between 1800 and 2400RPMs, it can't decide if it should run on 2, 3 or all 4 cylinders. You can't get a constant speed and it's as if it misfires, and timing will be a bit erratic right in that range. It's not a Defect or a Failure, but a Characteristic. All of those inline 4s do it. 100Hp, 115Hp, 125Hp. You probably spent many hundreds of dollars to correct a characteristic that can't be changed.
<br /><br />Do a search. You'll find lots of discussions about it. Most that have been posted were 115s, but 100s and 125s as well. It's a regular topic. <br /><br />There has to be a transition range when changing from running on 2 cylinders to running on 4. Merc engineered that transition to take place where almost nobody operates the boat ... plowing thru the water at just under planing speed. Most people get the boat up on plane or just idle around. At idle and up on plane, they run fine. The transition range is mostly noticed by people with beginning waterskiers and wakeboarders. Pontoons, too.
