Mercruiser 140 difficult to start when cold [FINALLY, SOLVED!]

[Neutron68]

The 1973 Mercruiser 140 engine that was swapped into my boat in fall 2014 runs, but it is difficult to start, after not running for a week.

I was told that the carb was rebuilt when the engine was installed in my boat.  I don't know how complete the carb rebuild was, however.  For example, I'm not sure if the carb fuel pump (called accelerator pump?) was rebuilt, too.
I can see that new fuel hoses were put on.  I believe that the mechanic put in new spark plugs, and would guess a new fuel filter, too.
He reused my nearly-new spark plug wires and updated electronic ignition distributor body and cap.
The mechanic winterized the engine after the swap.  The fuel tank was less than 1/4 full and Starbrite Star Tron Enzyme Fuel Treatment was put in the gas.  In the spring, I put about 10 gallons of non-ethanol premium gasoline in the tank.

I have been following the recommended cold-start procedure (push in the shift release button, pump throttle lever once to set choke, pump another time to squirt fuel into the carb), and the starter cranks and cranks without firing. 
I have found that I must pump the throttle lever 5 to 10 times and have the throttle at about 50% before the engine will fire while the starter cranks.  Then it dies as soon as the starter is turned off. 
After approximately 5 near-starts from pumping the throttle and cranking for 5-10 seconds, the boat will finally start.

After it finally starts, and still cold, it will only run smoothly at 1000 RPM or more. 
At 700 RPM, it barely keeps running.
This weekend, while in the lake, I turned up the idle set screw so the in-gear idle speed is 1000 RPM, to keep it from nearly dying when maneuvering at slow speeds around the dock.
With this higher idle setting, the in-neutral idle speed is about 1200-1300 RPM.

After the engine warms up to 140-150F, and I put it into gear to go out into the lake, I must increase the throttle slowly or the engine dies.  So, no fast takeoffs (forward or reverse) are possible.

What are the likely causes of these symptoms?
Poor fuel delivery?  (bad carb accelerator pump?  weak main fuel pump?)
Wrong carb mixture screw settings?

Eric

[Plugcheck]

Personally, I would go through the carb again, for me, you just don't know if unless you have a good mechanic.  Off idle slump and hard starting  are problems associated with a lean condition at idle, specifically the idle circuit.  Obviously check the choke for proper operation, but also take a feel of the throttle shaft and how tight it is in its bore.  Old carbs get worn here and suck air, causing a lean condition at low rpm.  Is it a Rochester 2gv carb?  Good carb when put together right. 

[75starflight]

Just curious what is your timing set at? I think my 140 is set at 4 degrees (the service manual recommends 6 degrees but idle is too high in my book) , and idles at around 650 to 700 rpm. Also, when you are playing with the adjustment screws you should have a vacuum gauge hooked up to the manifold and make sure you are getting the maximum amount of vacuum through the carb that you can.

I would start with timing and then resetting the carb adjustments with a vac gauge.

[Neutron68]

Plugcheck, it is a 2 barrel carb, likely a 1973 like the rest of the engine.
see:
http://i870.photobucket.com/albums/ab264/neutron68/Glastron/9b65ba1a-1737-4c58-89ae-068e46a2a505_zpsyrxyx5mj.jpg

Just curious what is your timing set at? I think my 140 is set at 4 degrees (the service manual recommends 6 degrees but idle is too high in my book) , and idles at around 650 to 700 rpm. Also, when you are playing with the adjustment screws you should have a vacuum gauge hooked up to the manifold and make sure you are getting the maximum amount of vacuum through the carb that you can.
I would start with timing and then resetting the carb adjustments with a vac gauge.

Timing setting...good question! 
The replacement engine I received does not have the little metal plate with the degree notations on it!!  With that gone, I don't know how to tell what the timing is!
I've been told that you can rotate the distributor assembly and go by how well the engine runs at the various amounts of rotation?

Unfortunately, I've got zero experience tweaking timing settings and zero experience tweaking carb settings.

And, I don't have a vacuum gage.  Are they expensive?

What about the idea of the carburetor pump (acceleration pump?) being bad?
Doesn't the difficult starting behavior and inability to accelerate quickly seem like a lack of fuel problem?

Eric

[75starflight]

I hate to say it but so did I when I rebuilt my 140. An vacuum gauge and timing light can be rented from O'Reillys or most auto parts stores. I have a spare timing cover I can get you the timing marks from and you could mark them on your cover so you can check your timing.

[Rosscoe]

You also never know if the carb has really been rebuilt. It may look clean but that doesn't really mean anything. Maybe the fuel filter is clogged with crap too?

[Maclin]

Is the choke plate closed when the engine is cold?  Could just need a choke adjustment.

[Plugcheck]

I had similar issues with my merc 140 (1980 vintage).  A rebuild, some new plugs, wires, cap, just basic tune up stuff and it ran great.  You are correct to assume if the accelerator pump is bad then it will fall flat getting to plane.  Pull the air cleaner, then use a flashlight as someone applies throttle.  Not running of course.  You should see two squitgun size sprays into the throttle plates, and the choke should rest closed.  Worse case send me the carb and a kit to match and I will rebuild it.  Getting your timing spot on will be a bit tricky without the tab.  One of the most important things to accomplish when assembling an engine is to check those marks.  Being off several degrees is not uncommon.  If it runs smooth when warm, I doubt the ignition us to blame.

[Neutron68]

Is the choke plate closed when the engine is cold?  Could just need a choke adjustment.

Yes, when cold, the choke fully closes when you set it with the throttle lever, and it fully opens after the engine runs for a few minutes.  This is a non-electric choke, by the way.

I checked the choke and found it working correctly when I was having trouble getting it started during the first startup of the spring.

You also never know if the carb has really been rebuilt. It may look clean but that doesn't really mean anything. Maybe the fuel filter is clogged with crap too?

Agreed.  I don't know how much of the carb was rebuilt, or how well it was rebuilt. 
http://i870.photobucket.com/albums/ab264/neutron68/Glastron/9b65ba1a-1737-4c58-89ae-068e46a2a505_zpsyrxyx5mj.jpg
The other thing I can't tell is how well it was or wasn't adjusted.  I would like to try adjusting the timing and carb before taking it apart and rebuilding it again.
All I can tell from the exterior is that there is a new gasket between the carb and the exhaust manifold.

I see inexpensive vacuum gauges range from $8-$25:
http://www.amazon.com/Vacuum-Gauge-OEM-Lower-Mount/dp/B00QXXIWGW/ref=sr_1_4?s=automotive&ie=UTF8&qid=1435074356&sr=1-4&keywords=vacuum+gauge
http://www.amazon.com/Carburetor-Valve-Pressure-Vacuum-Tester/dp/B00KRJFSFQ/ref=sr_1_8?s=automotive&ie=UTF8&qid=1435074356&sr=1-8&keywords=vacuum+gauge

Where do you connect the vacuum gauge, by the way?

I wonder if I can buy an old timing cover, cut off the little timing gauge part and somehow fasten it to the current timing cover?
Or maybe buy a new timing cover and replace this broken one. 
How much needs to get pulled off the engine to replace the timing cover?

There's an mechanic at the lake.  He fixes cars on a regular basis (engine repairs, brake repairs, body work, etc).
He may be able to adjust the timing and carb?  I need to ask him and see if he has experience with that.

From the responses, I'm getting the sense that if the timing is off, it may run well at higher RPMs but run rough at lower RPMs and make starting very difficult?
I'm also getting the sense that the carb adjustment is pretty important for starting and quick acceleration.

For now, I can live with the lack of fast acceleration, but the hard starting issue is a must-solve.

Eric

[thedeuceman]

for setting the timing, if you could get a look at a cover with a tab on it, you could mark the one you have to match.
depending on where the mark is. would be more difficult than having the tab there but may be better than just setting it by ear.

[75starflight]

From the responses, I'm getting the sense that if the timing is off, it may run well at higher RPMs but run rough at lower RPMs and make starting very difficult?
I'm also getting the sense that the carb adjustment is pretty important for starting and quick acceleration.

For now, I can live with the lack of fast acceleration, but the hard starting issue is a must-solve.

Eric

Eric,

I will take a picture of my spare timing cover and post it tonight.

On the removal of said cover, its not that hard, it just takes time.  these are the steps.
1. support front of engine
2. remove front engine mount
3. remove crankshaft pulley
4. unbolt and remove cover.

P.S. you can find a NEW timing cover for the 120/140 but is $150 plus freight. if you go the route of replacing it a used one is best and cheapest and ebay is the best place to find one.
http://bpi.ebasicpower.com/search2/show.php?q=timing+cover

http://www.ebay.com/itm/Mercruiser-Volvo-3-0-3-0L-2-5-120-140-P-N-59341-4-cylinder-TIMING-COVER-/191593319539?hash=item2c9bda0c73&vxp=mtr

[Rosscoe]

From the responses, I'm getting the sense that if the timing is off, it may run well at higher RPMs but run rough at lower RPMs and make starting very difficult?
I'm also getting the sense that the carb adjustment is pretty important for starting and quick acceleration.

For now, I can live with the lack of fast acceleration, but the hard starting issue is a must-solve.

Eric

Eric,

I will take a picture of my spare timing cover and post it tonight.

On the removal of said cover, its not that hard, it just takes time.  these are the steps.
1. support front of engine
2. remove front engine mount
3. remove crankshaft pulley
4. unbolt and remove cover.

P.S. you can find a NEW timing cover for the 120/140 but is $150 plus freight. if you go the route of replacing it a used one is best and cheapest and ebay is the best place to find one.
http://bpi.ebasicpower.com/search2/show.php?q=timing+cover

http://www.ebay.com/itm/Mercruiser-Volvo-3-0-3-0L-2-5-120-140-P-N-59341-4-cylinder-TIMING-COVER-/191593319539?hash=item2c9bda0c73&vxp=mtr

150.00!?
That's crazy and on top of the job?
I discovered my old 83 chev pickup doesn't have a timing tab either. I did adjust it by ear, but that's not the best. Its better than it was however. Pinging, no power and running on after I turned the key off.

[75starflight]

Eric
Here is a pic of the timing tab on my spare cover.
My 140 is set at 4 degrees before tdc

[Neutron68]

Eric,

I will take a picture of my spare timing cover and post it tonight.

On the removal of said cover, its not that hard, it just takes time.  these are the steps.
1. support front of engine
2. remove front engine mount
3. remove crankshaft pulley
4. unbolt and remove cover.

P.S. you can find a NEW timing cover for the 120/140 but is $150 plus freight. if you go the route of replacing it a used one is best and cheapest and ebay is the best place to find one.
http://bpi.ebasicpower.com/search2/show.php?q=timing+cover

http://www.ebay.com/itm/Mercruiser-Volvo-3-0-3-0L-2-5-120-140-P-N-59341-4-cylinder-TIMING-COVER-/191593319539?hash=item2c9bda0c73&vxp=mtr

Thanks for the listing of the steps to swap the timing cover!
Thanks also for the photo! 

I will look and see if I can find the edges of the broken-off tab.
If I know where the edges of the old tab are, I ought to be able to re-create the marks.

I'll look down the carb throat this weekend and see if I can see the fuel squirts.
Is the accelerator pump one the things that normally gets replaced during a carb rebuild?
Will I be able to see evidence that it was replaced without disassembling the carb?

Where does the vacuum gauge attach?
What fitting is needed to attach?
Some of the vacuum gauges come with a plastic cone on the end of the hose, which I suspect must be held in place by hand?

Eric

[Neutron68]

On the accelerator pump, does that come as part of a carb rebuild kit?
And can the accelerator pump be changed without complete carb disassembly?

[Hyperacme]

Have you looked thru the "On line service manuals" here ...

http://boatinfo.no/lib/library.html

Another site with helpful info ...

http://www.maxrules.com/

[Neutron68]

Have you looked thru the "On line service manuals" here ...

http://boatinfo.no/lib/library.html

I've been here before.  Oh gawd, looks like a fair amount of disassembly to get to the accelerator pump.
see :
http://boatinfo.no/lib/mercruiser/manuals/mercruiser3.html#/512

My goal was to have the whole boat running in near-perfect condition by the July 4th week. 
I don't see that happening, unless the mechanic at the lake can do something in the next 5 days...

Eric

[dorelse]

It takes all of 5 minutes to get the carb off and opened up...at least on my 305 anyway...really not a big deal at all.  I'd be starting with the simpler stuff first though...screen on the hard fuel line into the carb clean?  Do you know the fuel pump is ok, tested it?

[Neutron68]

No, I have not tested the main fuel pump.  (how often do they need replacing?)

I can check that carb fuel screen this weekend.  That looks like a simple wrench operation.

Aren't the symptoms good indicators of the problems?

1.  engine seems starved for fuel when trying to start (accelerator pump?)
2.  engine nearly dies if you punch the throttle (accelerator pump?)
3.  engine does NOT die if you accelerate slowly
4.  once engine is running it stays running (main fuel pump ok?)
5.  engine doesn't run smoothly below 1000 RPM
6.  engine runs fine at high RPM (main fuel pump ok?)

[Hyperacme]

" I'd be starting with the simpler stuff first though... "

Good advice ...
Could save you a lot of time and money !