On Sun, 4 Feb 2018 18:37:35 -0000 (UTC), Bill
wrote:

wrote:
Did you ever figure out why your 3.0 Merc wouldn't idle when warm? I have
the same problem. Would appreciate any advice. Thanks
Todd


You probably need a carb cleaning. Low speed idle circuit plugged.

+1
That sounds like a carb problem to me. If it was an outboard I might
have other ideas but this is basically a car that doesn't idle.
If this has idle screws, Back them out 2 or 3 turns, crank it up and
with it turning 2500 RPM or so, slam your hand over the carb throat.
The high vacuum and rich mix *might* suck the crap on through. Then
run them back in and back out to the starting point (usually 1 1/2
turns) and adjust from there.

wrote:
On Sun, 4 Feb 2018 18:37:35 -0000 (UTC), Bill
wrote:

wrote:
Did you ever figure out why your 3.0 Merc wouldn't idle when warm? I have
the same problem. Would appreciate any advice. Thanks
Todd


You probably need a carb cleaning. Low speed idle circuit plugged.

+1
That sounds like a carb problem to me. If it was an outboard I might
have other ideas but this is basically a car that doesn't idle.
If this has idle screws, Back them out 2 or 3 turns, crank it up and
with it turning 2500 RPM or so, slam your hand over the carb throat.
The high vacuum and rich mix *might* suck the crap on through. Then
run them back in and back out to the starting point (usually 1 1/2
turns) and adjust from there.


My T8 Yamaha had same problem. Had a tiny place speck on top of the idle
jet when I took the carb apart. Added a good filter just before the carb.
Jets are so tiny, that the least bit of detritus plugs them.