Re: 1988 Mariner 175 idle flucuation
Probably the idle stabilizer module acting up. You can disconnect it to check the theory. Mercury doesn't stock the part 'cause nobody buys it. They just chit can it.
On the other hand, you might be loading up because of a leaking needle or gaskets, and the idle stabilizer module is trying to compensate.
It is the module that is wired into the bias circuit on the switchboxes. That is the terminals that are jumpered together, right beside the stator terminals. Usually it has one wire to a stator terminal, and one to the bias terminal. It works by changing the bias, pulling it down, thus advancing the timing if the idle speed falls below a preset speed, usually 600 rpm. The same module might advance the timing at 5000 rpm also. Your link n sync spec would specify 19 degrees WOT timing if that's the case. The module makes up the other 4 degrees, then pulls it back 6 degrees at 5500 rpm.
Disconnect it, set your idle where you want it, and WOT timing to 23 degrees. Might as well do a formal link n sync while yer at it. Not much more work, and you know adjustments are in the ball park. If you're propped on the low side, it'll really wake up at the top end.
hope it helps
John
