I would check your TPS if the above don't help. With your discription in post #2 it sounds like the computer isn't getting solid info from your TPS (throttle position sensor) .

Just putting that out there.

Never, never, never assume that because it's new-right-out-of-the-box that the part is any good. Been F'ed by that one before.

Also, don't assume that just because the box says it's something, it really is.

Also, don't expect that any two of the same identical items is actually identically the same. I just went through this with our inventory of belts- all for the same engine on the same year trucks. Out of 11, 3 were the same length. The others were either loose to the point they slipped or too tight to go on.

Good point- if you're able to look at live data, you may see some "junk" at certain positions. Sometimes it can be very intermittent.

if you don't have a mercruiser scanner, buy one. really makes this sort of thing much much easier... they are around used and no matter what you have to pay for it, it will pay for itself in short order just in not having to buy the wrong parts because you are guessing.

Ray The stock regulator looks like a sealed unit. can I just break the seal?