Re: cold blooded, ruff ideling 85'ish Evinrude
with reference to a new t.stat, will assume the motor is pumping water and running at the right temp (not a cooling problem). Start with fresh gas and oil in the right mix. If the motor is running well enough to take it out, try running it for a while and see if it smooths out -- perhaps with some tweaking of the carb adjustment needles (could be running a little rich, for example). If still not up to par, a partially clogged jet would be a good guess, and the resolution would be to remove and clean the carb -- perhaps rebuild it.
