1976 Mercury 1150 Idle Adjustment

[1976Merc1150]

Hey everyone! I'm new to this forum. I'm 30 years old and have grown up with 1970s Mercury outboards and don't want to go with anything else.
I have a 1976 Mercury 1150 short-shaft outboard. It runs great-good take-off power and good top end. She just has a bit of a low idle, sometimes so low that I need to run the fast-idle lever in order to put it into gear without stalling. I was wondering if it would be safe to turn up the idle just a bit by that 'bolt stopper' on the side of the distributor. Any help is much appreciated! Thanks!!

 

[emckelvy]

To increase idle speed, you would adjust the "Idle Stop" on the "Stop Bracket" that mounts to the front of the distributor. Don't touch the "Throttle Stop" or Spark Adv" screws unless you're doing a more extensive tuneup.

Loosen the locking nut and turn the screw inwards (CW) to increase idle speed. Once you have found the correct idle speed, you'll need to readjust the preload on the throttle cable. When the control box is in Neutral, you want the throttle cable pushing the distributor into the throttle stop, with just enough force to allow it to repeat every time you increase throttle and then take it back to minimum speed.

If the cable preload is too loose, the distributor won't come back to the stop every time. If too tight, the fast idle lever won't work properly and the throttle may bind.

Best thing to do is to get the boat out in the water, warm the engine to full operating temperature, and adjust idle speed/idle mixture for best idle without a "lean bog" when you accelerate. These old Mercs don't have an acceleration pump, so they like to run a bit rich (i.e. "lumpy") at idle, then they don't die out when you suddenly accelerate (like taking off with a skier).

Once you have the idle mixture set, then do the final "tweak" on idle speed, get the lowest, stable idle you can. Test for off-idle "bog", and if it has a clean acceleration, make a final adjustment to the throttle cable preload, and you should be good-to-go.

You may find this excellent writeup on Link n synch procedure useful; it's the best way to get the old Towers of Power tweaked-in.

http://forums.iboats.com/forum/engi...ing-and-sync-of-merc-inlines-to-1988?t=168855

HTH................ed

 

[1976Merc1150]

Thanks so much for the great answer! Just a question- do I need to adjust the 'idle speed' 'idle mixture' screws, or can I get away with solely adjusting the idle stop screw along with the cable. And in regards to the adjusting the cable, we are speaking about the throttle cable and not the fast idle lever cable, correct?

Thanks again for all the help. I love my motor and want to keep it perfect.

Thanks!!

 

[Chris1956]

Since your acceleration is good, there is no need to change the idle mixture settings on the carbs. Turn just the idle stop screw CW a bit, as was recommended. If you turn it a small amount, there will be no need to adjust the throttle cable either. If you need to adjust the throttle cable, leave the throttle in neutral and loosen the throttle cable barrel nut a turn or two. You still want some preload on the throttle cable to assure the throttle is pushed shut, when you go to neutral.