Help with early 80s mercruiser 140hp

[Kailofsouls]

I have a older mercruiser 181ci 140hp 4cyl. Serial number starts as 67 I believe it's around an 82-84. Couldn't get it running after I had a mechanic replace gimbal bearing.
After fighting with it and another mechanic even gave up on it, I found that the fuel pump diaphragm was bad dumping gas into the engine block.
Replaced the pump, did full oil change, cleaned carb, replaced idle mixture screw (had a very slight ridge on it) tried setting from 1 to 2 turns out. I can't get the motor to run for more than a few seconds.
I bumped the engine around till cylinder 1 was 6° btdc grounded plug to motor and hand set timing listening for the spark per mercruiser service manual #3. I honestly don't know if that was right to do, but I couldn't get it to run enough to use the timing light.
Dose anyone have any ideas for thoughts?
I don't know what the compression is but the last mechanic I took it to said compression was good.
Thanks for your time and help everyone.

 

[Bondo]

Ayuh,....... Does that motor have points ignition,..??

Did you service them,..??

 

[Kailofsouls]

I ran a small piece of 600 grit sandpaper on the points came out clean. I don't have a feeler gage but everything is tight. So I don't see how it could have changed.

 

[nola mike]

I ran a small piece of 600 grit sandpaper on the points came out clean. I don't have a feeler gage but everything is tight. So I don't see how it could have changed.

Checking timing, points and compression is very basic troubleshooting. Sounds like you've eyeballed 2 out of 3, so they're almost certainly off

 

[Bondo]

Ayuh,..... So pull some plugs,... Are they firing,..?? Is it getting any fuel,..??

 

[Scott06]

Id start with a few basics use a spark gap tester to make sure your spark can jump a 1/4” gap or more. If the fuel pump was over flowing quite possible the plugs are fouled. Maybe turn the idle speed screw in / up a bit, fatten the idle mix up a hair. Leave the distributor loose so you can turn it while cranking to see if you can time it by ear enough to keep it running. Also make sure there is no vacuum leak at base of carb, usually the kits have several gaskets possible the wrong one was used

dribble a little fuel down the carb to see if it fires , assuming you have spark. Quite possible carb isn’t fully clean. Also do t assume because the points worked before they work now . They get corrosion just sitting there

 

[ESGWheel]

As you are probably familiar with there are three basic ingredients needed for an engine to run: compression, spark and fuel. Many other items needed, like correct timing but those are the basics.

Given the mechanic’s expression of good compression and that the engine starts but sputters out - for the moment - we’ll assume you have compression and spark. So, onto fuel. A real basic check is to with key off, remove spark arrestor and using a good flashlight look down the throat of the carb while a helper moves the throttle lever all the way forward to WOT in a smooth stroke. Do you see a squirt of gas like a syringe being depressed? If no, then you have a fuel problem.

My suggestion is to perform the squirt check and post results. If good, still might be a plugged carb, but then onto spark / timing as well as validating compression.

 

[ESGWheel]

Quick follow up: if you are planning on maintaining your engine / boat yourself I encourage you to get some basic hand tools and a dwell meter to properly set the points. For old school guys like me that means (at the time) an expense Craftsman Dwell Meter. Fortunately, these days they make a modern multimeter focused on old style points type ignition like this link which also serves as a multimeter. Way cool and fairly inexpensive. Another great tool to have is a compression tester, again fairly inexpensive (link).