1976 Chrysler 105 running rough immediately after adjusting carbs on the water.

SlowSL

Cadet
Joined
May 26, 2016
Messages
15
My motor had ran really well for about an hour or two, until I decided to fine tune the carbs. Could just be coincidence, but it started acting up immediately after I made some adjustments. I had made this adjustment in a bucket, out of the water, but the instructions say to do it in gear, on the water. The needles were put back into the exact same position as before, FWIW, so everything should have been where it was when it was running well. It was running rough, was hard to keep idling, had to crank the idle bolt all the way down to keep the carbs cracked open enough that it wouldn't die. There was also noticeable unburned fuel I could see shimmering in the water, and a slight bit more smoke from the exhaust. I tried turning the needles a bit one way, then the other, but didn't seem to make any difference. At home, I did the cylinder drop test, but it was hard to note any change while shutting off to ground each wire (CDI ignition). I did another test by having all wires plugged in, and leaving the motor just barely idling, not touching the throttle lever at all during this test. I then would shut off, pull one plug, turn back on, and doing so on every cylinder, it would not even come close to starting. Plug them all back in, and it would start and idle. I also used a spark tester with a gap and verified a strong spark on all cylinders. Plugs are almost brand new and looked fine when I pulled them. I'm guessing the next thing I should look into is the carbs? What should I try next?
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
18,112
First thing you do when trouble shooting an outboard is a compression test.
Compression can change.
Also check the fuel for water, then pull the fuel pump apart and check the diaphragm for holes or tears??
ONE!!!! backfire or cough or stutter can blow a hole in the diaphragm.
If it's bad? get 2 and keep a spare.
 

CaptnKingfisher

Petty Officer 1st Class
Joined
May 14, 2017
Messages
259
Since it was running well until you adjusted the idle mix, and then you also adjusted the idle speed, I would suggest redoing this the correct way. You need an accurate tachometer to do this correctly. First set your idle speed according to your service manual. If your manual recommends 700 rpm, and your doing this on muffs, I've been told you should set it to 1100 rpms. You may need to fine tune this later in water. Then to set your idle mix correctly you want to turn the screw clockwise slowly until rpms drop due to lean condition (if rpms are dropping immediately, you may be too far in already), then turn the screw counterclockwise until rpms begin to drop due to rich condition. Now you've got a sense of the upper and lower end of the spectrum, now you want to turn the screw clockwise again slowly and set it for maximum rpm and engine smoothness. If this doesn't fix the issue then we can start hunting down other things.
 
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