'77 Mercruiser MCM 140 won't fire

[Tiger123245]

I bought a '77 Starcraft Capri 17 a few months back. It's got the MCM140 motor in it. Guy I bought it from said it ran fine last summer and he had the engine tuned-up just prior to winterization.

Darn thing won't start! I put a new battery and spark plugs in - wires and distributor looked new so didn't mess with them, and fresh gas. And just so ya'll know I am NOT a mechanic. I can do the basic stuff on my car (change oil, plugs, battery, etc.) - but you start talking about taking things apart and I need detailed instructions.

I put the muffs on and turn the key and the engine will crank over but not fire. I checked the plugs today after work they all spark fine - had my mom turning the key while I checked for spark and the motor actually started with one of them out - sounded like hell - but it ran for a minute anyway before dying. Kinda stumped on how to proceed from here.

Any advice I get before Mon. I'll give a shot otherwise I'm going to take it to the local boat/rv shop and probably pay out the nose for them to look it over.
Thanks in advance!!!

 

[Bt Doctur]

Re: '77 Mercruiser MCM 140 won't fire

Exactly how are you trying to start it?
working the throttle once or twice first or just turning the key?
Choke working correctly?

 

[cannonford57]

Re: '77 Mercruiser MCM 140 won't fire

3 things you must have for the blessed gods of internal combustion will come visit are fire,fuel,compression...u have fire so with the engine spinning spray a bit of carburator cleaner (or wd40)if its all u have in the carb...if it starts u have a fuel delivery issue...needle and seat stuck....if not go back to #1,fire.maybe a set of points installen and properly set will bring u to life

 

[IVAZ]

Re: '77 Mercruiser MCM 140 won't fire

Have you dealt with a carbureted engine before?
Like the Doc here is saying, pump the throttle a couple of times before you fire it up. You should also give it a little throttle before you turn the key. Tell us how youre trying to started before you take it to a tech.

 

[IVAZ]

Re: '77 Mercruiser MCM 140 won't fire

3 things you must have for the blessed gods of internal combustion will come visit are fire,fuel,compression...u have fire so with the engine spinning spray a bit of carburator cleaner (or wd40)if its all u have in the carb...if it starts u have a fuel delivery issue...needle and seat stuck....if not go back to #1,fire.maybe a set of points installen and properly set will bring u to life

This will work but I think one to two ounces of gas down the carb is a little healthier for the engine.

 

[Tiger123245]

Re: '77 Mercruiser MCM 140 won't fire

Just turning the key. This is an older boat than any I've had previously and no manual for figuring out where things are. Where would I find the choke? Sorry if it sounds like dumb questions - but I really am clueless here. Will try the throttle back and forth tomorrow after work. If that doesn't work, spraying some WD-40 in the carb and give that a shot.

 

[Bt Doctur]

Re: '77 Mercruiser MCM 140 won't fire

go to the adults only section and download the manual for that engine and the factory installation one

 

[ziggy]

Re: '77 Mercruiser MCM 140 won't fire

i think ya need to go to the adults only sticky. http://forums.iboats.com/showthread.php?t=288430
read #5. if you do not understand what's being said there. you can find the facts in #9. for a 77 i think ya use service manual 2. confirm proper manual by serial number. if you don't have a minor grasp of what's being talked about in the service manual. your best bet might be your local boat shop.. to elaborate on what bd said. for a cold start. use the shift release button so the throttle is all that is being operated by the remote. one full stroke to stop should set the choke. give it one or two more full strokes and then set it to about 1/4 throttle. try to start it. if it starts, be ready to throttle back to an acceptable rpm.

the choke is the flat plate at the top of the carb. it will be vertical when warm, horizontal, but not fully closed when cold and choked. you set it by one full stoke of the throttle at the helm. release the shift with the button on your remote control. mines black and in the center of the pivot point of the throttle lever, i push the button in and move the throttle/shift lever fwd with the button in. this button keeps the drive from shifting into fwd. yours may be somewhere else.

 

[IVAZ]

Re: '77 Mercruiser MCM 140 won't fire

The choke is on the carb.
When you try to start it give it one full stroke of throttle to set the choke then pump it once or twice more. Then advance the throttle about a quarter of the way. If everything is operating as it should, it will fire up.
Be patient when you dowload the manual because its a huge file.
Let us know how it goes tomorrow. Good luck.

 

[IVAZ]

Re: '77 Mercruiser MCM 140 won't fire

ziggy,
You type faster than me. You also explain things better.

 

[Tiger123245]

Re: '77 Mercruiser MCM 140 won't fire

Thanks guys! Working the throttle back and forth before turning the key did the trick - it helps that I found the choke button (I think) but it fired and stayed running in forward and reverse and idle. Thanks a bunch!

 

[Fishermark]

Re: '77 Mercruiser MCM 140 won't fire

it helps that I found the choke button (I think)

Glad you got it going.

There is no "choke button." The choke will automatically close when the engine is cold and then gradually open. By operating the throttle handle a couple of times you are actually squirting a little gas into the carb via the accelerator pump and "setting" or closing the choke plate. The good news? All that happens without you needing to know or do anything about it other than operate the throttle a couple of times.

The "button" you found more than likely is the button on your shifter that bypasses the actual shifting mechanism and allows the throttle to be operated by itself. Like keeping it in neutral while you give it some gas.

 

[Tiger123245]

Re: '77 Mercruiser MCM 140 won't fire

Thank you for the clarification... that makes more sense than what I was thinking. So the button is probably the shift release. This is an older model - my previous boat had the shift release actually on the handle. This is just a lever throttle. My father is coming to visit my daughter and I next weekend so I think I'll talk him into tuning up the engine for me while he's here since it did sound kind of rough when it was running. I downloaded the manual - good god! 3 hours!