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Idle problem 1987 Mercruiser 37L 165

vkeiper

New member
"Hi,
I just bought this boat


"Hi,
I just bought this boat and was having a problem keeping it idling. When I first start it, I have to pump fuel into carb twice, by pushing the throtlle control forward and back to neutral twice to pump fuel into the carb (via the accelerator pumps), then when its cold it will crank over and fire right up and idle. Its a little rough, but it will idle. Then if I let it warm up for like 10 minutes (using muffs to run water through to cool of course). It seems to run at @140 degress at idle out or gear. Then if I shut it off and try to refire it will not idle, If I put into gear and bring it up in RPM's it runs fine, revs good runs smooth, just wont idle. I have found if I put my hand over the top of the carb it will run much better. The choke is opening up all of the way once warmed up. I was thinking it was a vacum leak, but there is no vacuum lines on the motor that I can see.
It sat for 2 years, was winterized by marina.
So, took the next steps.
1. Tune up
a. points(gap .022),condenser,rotor,cap, plugs, wires. I set the gap by rotating motor till the lobe that opens points was opening old points at maximum then installed new ones and set to specified .022 gap. I read something about dwell in the manual, but did not play with that at all
Should I worry about that?
P.S. I checked inside of the distrib for oil, it was dry. (my paps boat had prob where a seal went bad and oil leaked up into points)

b.Drained fuel tank and lines refilled fresh fuel, put in some dry gas in for safe measure.

c. changed fuel filter in carb, there was none pre fuel pump

d.tried playing with the timing, not to much help there, still runs the same.

e. checked the coil ground, seems fine

The carb is an M2/Mercarb, i have not taken this apart yet, assuming this may be the source of my problem.

I figured I would check the float operation, Plus I see fuel dripping into carb once the motor first stalls.

What else should I check in the carb that effects idleing?

Any other things to check that could effect the idle?

A totally different issue, the darn water cooled regulator I shot also! I am going to fabricate a bracket and mount a GM alternator to fix that. Those regulators are like $400!!"
 
"vince-
2 things I found tha


"vince-
2 things I found that gave me trouble at idle- The ballast resistor cracked the ceramic, and the thing wouldn't run smooth for anything!
The last time I had trouble at idle speed, I rebuilt the carb. the rebuild kits (for the older carbs) are rather cheap, and it only took a couple hours. Man what a difference!
hope you find your trouble
Jeff"
 
"The engine is running lean. W

"The engine is running lean. When you cut off the air supply, it runs better. You might have a vacuum leak, or you may need to pull the carb and have it rebuilt. There may be a bunch of debris at the bottom of the float bowl blocking the main jets."
 
Vince.
I did stop reading whe


Vince.
I did stop reading when I got to where you said I did not do anything with the dwell.
Tune up 101.
The dwell is another form of telling the gap of the points.
This is done with a meter instead of a feeler gauge.
The point gap is much closer when set with a dwell meter than when set with a feeler guage.
If the points are to wide(to much gap) the engine will not idle well.
On the other hand if the points do not have enough gap the engine will not run well at higher rpm.
If the idle mixture screws at the base of the carb will not correct the idle try resetting the points with a dwell meter.
 
"Thanks, guys
I am going to r


"Thanks, guys
I am going to read up setting the points using dwell and check for bad intake or carb gaskets and also remove the top off the carb and check for debris.

I will post my results after I check it out."
 
"Just figured I would put my r

"Just figured I would put my results in here to help anyone else out who may search on this type of issue.

Got it running great!

1. Rebuilt the carb (Sierra kit, bought this site - was shipped to my house in ONE DAY) (varnish and dirt in bottom of fuel bowl) cleaned the jets and replaced float assembly and accellerator pump.

2. After I rebuilt carb I check the Dwell, it was 37, When I installed the points I just set the gap with a feeler gauge but I must have been pretty accurate.

3. The hardest part was adjusting the Idle mixture. Once my dad told me how to do it, it fired up and worked great. The book said turn it in till it stopped and then back it out 2 turns. That got it running but to fine tune, I turned the screw 1/4 turn at a time and waited 20-30 seconds and monitored the tach until I got the highest idle. From there I took it out on the lake and it runs great!

Thanks for the help guys."
 
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