Merc 140 carb question

[DennisM]

Hello all,

Just want to say thanks to all who have helped me get this far! I finally have the boat in the water, trim works, new starter, new steering cable and helm, new impeller..

It starts great cold, runs good, temp stays about 150-160, even idling. The idle is low at around 600rpm, and once warmed up only idles around 700-800 and get rough. Once warmed up if it dies or I turn it off, I have to give it a lot of gas to get it to fire again.

New plugs, cap and rotor.

I am thinking I need to bump the idle a tad but do not know what carb is on it to find out how.

Any direction here would be greatly appreciated. Also top speed at WOT is about 25 according to speedo at about 3900rpms.. I do not know what pitch prop is on it.

EDITL: Sorry, forgot to mention its a 1986 mercrusier 140, 3.0/4l on a 86 four winns horizon 190

 

[tschmidty]

Re: Merc 140 carb question

There are a couple of idle adjustments which you can find in the manual. Idle speed is on the linkage where the throttle cable comes in and then idle misture which is on the bottom of the carb coming out of the base plate.

WOT RPM is low and at that speed you are probably running a small prop, 15" or so.

 

[fishrdan]

Re: Merc 140 carb question

New plugs, cap and rotor.

Points and condenser??? (Don't forget to set the dwell and then timing.)

If the carb has 2 idle mixture screws it's a Rochester 2GC, if it has 1 idle mixture screw it's a Mercarb. The engine should idle higher (1000rpm?) while warming up, then settle back to 700-800RPM when the throttle is opened and it comes off the high idle cam. It sounds like the choke isn't working correctly since it idles at 600RPM cold, then raises up when warm. It should do the opposite, idle higher when cold, the choke and high idle cam will bump the engine speed. Final idle settings should be done while the boat is in the water, warmed up and idling in gear. Your 700-800RPM idle on land should put you close to the 650-700RPM in the water/in gear setting, but you still need to fine tune it on the water.

The manual for your engine are in the "Adults Only" stick at the top of this forum, lots of good info.