57 idle speed

"I have a pair of 5.7 merc, I

"I have a pair of 5.7 merc, I am noticing that when both engines are started that they idle (temp at <100 degrees) aroung 500- 600 rpm as the temp raises (145 degrees) the idle increases to about 700-800 RPM. Is this normal operation or should they start then jump to the 750-800 RPM immrediately?"

"Sounds normal to me. Oil can

"Sounds normal to me. Oil can be a little thick on a cool morning. There is no fast idle on a marine engine during warm up. I will throttle up to about 1000 RPM for a warm up after I start. After a few minuets, I'm good to go.
Chris"

I am guessing they are carbed.

I am guessing they are carbed.
At normal operating temp the idle should be about 650 RPM in gear. If its higher than this adjust it down so as to minimize wear on your drives when shifting into gear.
Warm up in neutral at 1000 or so in neutral as Chris says. Use your shifter lockout button on your throttle quadrant.

Rod

"You are correct they a Q Jets

"You are correct they a Q Jets (4B) I had one side rebuilt at Percision Carb, the other side was not done. I tried to adjust the idle so that the engine sync stays in the middle of the gauge, difficult task. I did notice the other day that one engine has a serge in RPM while under way (the side that did not have the carb rebuilt) I will see what happens when I put the engines in gear,they should drop down to 650? if not I will post another thread on how to adjust them. It seems that one side has a torqs screw, and the othe engine has a brass barol and nut. At this time they idle between 750-800.(While not in gear.) Thanks for all the advice
1990 280 DA
T5.7 "Summer Wind""