Rough idle at startup, fine once warm

[intrepidvoyager]

Re: Rough idle at startup, fine once warm

I think the thermo for a 3.0 Mercruiser is as follows ..Opens at 140 degrees


Sierra? Thermostat Kit for Mercruiser? 140 / 3.0L Engines

Proper thermostat operation is key in getting peak performance and maximum fuel efficiency! This marine-grade Kit will withstand the rigors of "ugly" brackish and saltwater.

Sierra? Thermostat Kit (part no. 18-3650) includes thermostat and gasket to replace your original thermostat kit (O.E.M. 59078Q3).

 

[Fisnfool]

Re: Rough idle at startup, fine once warm

Carb Ice. Not that is a neat explanation of something I have hear of but never heard the name.

Wow. Did I write that?

I should not use the keyboard when on Morphine.

Should have been:

Carb Ice. Now that is a neat explanation of something I have heard of but never heard the name.

Now to get back on topic:

I have a 110 3.0 L too. It is a 1965. If your thermostat casting is the same, a car thermostat will not fit. Could be yours is stuck open or missing or stuck.

I had the impeller fail once and the engine overheated. This opened the thermostat so wide that when it cooled and closed, it was actually cocked to an angle and stuck open.

I also noticed your comment on vibration at the start of the thread. I'll have to do a compression check on mine to see if a vibration I have at about 5 mph is related to a cylinder missing. But with mine, it is smooth above and below this point. Top speed in a 19 footer with all the gear and four LARGE adults is 30 mph gps. So I never suspected that I may be missing at lower rpm's.