Hi, 2 things that may go together: I've owned this 150 HP Mercury EFI for three years, and it's always been a rough idler. It's on a 1999 StarCraft open bow/runabout 18'. Once the RPM's get increased it definitely smooths out. This outboard is a real 'beast' on this boat then. Correspondingly, the water stream for cooling is kind of weak and sputtering at the same time. I do have a high-heat alarm, and it has never gone off. I had the impeller and seals replaced when I got it three years ago. Other people I have talked to said they would expect the stream to be more of a steady stream/'peeing'. Although better, it does seem kind of 'sputtering' rather than a real nice steady stream at higher RPM's also. I had it tuned up at that time too and checked for engine compression, etc. as to the rough idling. I had one shop service guy tell me that Mercury EFI outboards of that size and year range are known for that kind of rough idling. So the questions are:
1. Do others here know of that behavior with these types of outboards running at idle like he says, and if so is there much you can do to improve? and
2. What about the water stream for cooling, does that go hand in hand with that kind of idle?
Thanks!
1. Do others here know of that behavior with these types of outboards running at idle like he says, and if so is there much you can do to improve? and
2. What about the water stream for cooling, does that go hand in hand with that kind of idle?
Thanks!