Mercruiser 140, starts when cold, won't start when hot?

[75starflight]

I have a good block and head sitting in my shop here in Nebraska if you need it. It was a mercruiser 120. Block casting #s were the same as the 140 I replaced it with.

Oh, I will sell it cheap too.

Thank you for the offer. 
I checked the manual that came with the boat and it shows a difference in cylinder bore between a 120 and a 140. 
Did your 120 have up-sized pistons?

Eric

It is a 4 inch bore I believe.  But as stated before a good rebuild will cost around 2 to 3 thousand. I built my 140 and looking back with everything I had to purchase I would have picked up a crate engine from Michigan motorz if I were to do it over again. 

[Neutron68]

I'm amazed and annoyed at all the derailing I'm getting from almost everyone I tell about the state of the boat engine!
They are applying a used car mentality to this.  The part they don't get is that I spent a lot of time researching the boat and fixing as many problems myself as I was able.  Clearly, people treat vehicles as disposable things - use em up and throw them away.

It's not worth putting a new engine in it.

Just throw it out and get a different boat.

Why don't you buy a newer boat?

Why don't you buy a pontoon boat?

I need help from people who understand not wanting to throw out a boat just because it has a problem!

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[Plugcheck]

I can understand your frustration, many of have been on that door step more than once.  Right now I'm curious to hear about the lake testing concerning water in cylinders.  Runs great on hose, but gets water in all four cylinders when on the lake is about the oddest issue I've heard to date.  Don't lose hope till ya know for sure what the problem is.

[Neutron68]

I didn't have time to lake test the boat today.  I spent the day towing it from Excelsior back out to Paynesville and rolling into the garage.

The local lake mechanic out there answered my question of how hard it was to get to the head and head gasket.  He said it would take him 5-6 hours of work to get to the head gasket.  Sheesh!  No wonder Dan Luke didn't volunteer to look at the condition of the head and head gasket!

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[75starflight]

Sorry, but 5 to 6 hours is a bunch of bull. When I tore down my 120 or 140 it took me maybe an hour. It's six bolts to remove the intake/exhaust manifold with the elbow and carb attached. four bolts to remove the valve cover. Two bolts to remove the thermostat housing. And I think 8 or 10 bolts to remove the head. And a good impact can make quick work of everything.

[Plugcheck]

     Therein lies the difference from what time it takes to what time is charged.   Or, in the mechanic's defense he was quoting the time to replace the head gasket.  Heck you were halfway there with the intake/exhaust manifold removed.   I would lake test first, then determine the next step.  A head gasket bad just would not put water in all four cylinders, two maybe, catastrophic failure maybe 3 cylinders, but all four?   Let us know, I just cant see water getting in just from the lake, the same cooling system is used on a hose. 

[Jason]

Yea, water in all four is strange for a head gasket or even a crack IMO. Has to be coming in through intake/exhaust somehow. Does that bolt on cover on the intake seal anything other than just air? I know the 140's don't have this. Could there be something in the exhaust of the outdrive blocking water and exhaust from escaping? Mouse nest? Maybe you could remove the exhaust bellow and run it like that and see if that makes a difference.

[Neutron68]

Yea, water in all four is strange for a head gasket or even a crack IMO. Has to be coming in through intake/exhaust somehow.

We now know the exhaust elbow and exhaust manifold are not leaking water from their water jackets.
This is the 4th summer I've had the boat and it did not happen the previous 3. 
This suggests something changed/broke.

Last summer, when the outdrive's impeller was malfunctioning, there were a couple of occasions (during diagnosis process) when the temp gauge would briefly climb to around 200 F, and I would immediately throttle back to idle let the engine cool off.  During that time, I never went above 2000 RPM, because I didn't want to overheat the engine. 
Could those brief periods when the temp spiked to 200 F cause an engine head crack or block crack?

Does that bolt on cover on the intake seal anything other than just air? I know the 140's don't have this. Could there be something in the exhaust of the outdrive blocking water and exhaust from escaping? Mouse nest? Maybe you could remove the exhaust bellow and run it like that and see if that makes a difference.

Dan Luke ran the engine for 30 minutes in his driveway.  He's an outdrive specialist and regularly deals with the exhaust system (exhaust bellows, outdrive exhaust path, etc.).   I would expect him to notice a blockage in the exhaust system when he took off the exhaust elbow and when he ran the engine.  I would bet a blockage would change the exhaust sound or amount of water flow, etc.  I would expect him to notice that kind of difference.

Additional info:  Dan said he did some research and was told that the 1978 Glastron SSV-177 did not ship with an exhaust flapper.

Eric

[Jason]

I don't think my 74 has a flapper either. 200 degrees won't hurt the motor. Car engines run that all day long. The bigger question is, what was causing that?

[Plugcheck]

       I suppose any engine pushed too hot can develop issues, just did that on my Rude 115, chunks of impeller from old water pump clogged up pipe.  Cleaned out and checked, no permanent damage.  Hot enough to boil water off the head, so I doubt you caused any issues at 200.   time for you to lake test, my bet is on the elbow gasket.

[Neutron68]

I don't think my 74 has a flapper either. 200 degrees won't hurt the motor. Car engines run that all day long. The bigger question is, what was causing that?

The outdrive impeller had several of it's fins angled in the wrong direction.  We're not sure if the impeller was installed improperly or if it got rotated backwards (by turning the prop backwards, with the outdrive in gear) by the mechanic doing the engine swap in fall 2014.  I'm betting it was the 2nd possibility.

[Neutron68]

I got compression pressure readings from Dan last night:
cylinder 1 - 145
cylinder 2 - 145
cylinder 3 - 120
cylinder 4 - 135

The specs for a Mercruiser 120/140 are 140 psi.

[Plugcheck]

     Personally I wouldn't get too excited with a low cylinder unless it was just rebuilt.  Just a thought, but when you stated that water was coming out of all four spark plug holes, was the intake/exhaust manifold connected?   Its a long shot, but could a bad head gasket in one cylinder blow water into the exhaust manifold and then be sucked up by the other cylinders?  Its a way long shot, I still have trouble understanding how it runs perfect for 30 minutes on a hose in the driveway, but hydro locks when in the lake?

[Neutron68]

     Personally I wouldn't get too excited with a low cylinder unless it was just rebuilt.  Just a thought, but when you stated that water was coming out of all four spark plug holes, was the intake/exhaust manifold connected?

The engine has been fully assembled whenever I've run it, tried to start it or blown water out of the cylinders.
The only time the exhaust manifold has been off was when Dan took it off to pressure test it and examine it.  He never mentioned it so I don't think think Dan cranked the starter in that state.

I still have trouble understanding how it runs perfect for 30 minutes on a hose in the driveway, but hydro locks when in the lake?

Dan theorized that maybe the water breech only leaks when the water pressure from the water pump is high enough (with higher engine revolutions).  Running it in the driveway doesn't allow the water pumps to produce as much pressure, so it doesn't leak water.

Eric

[Plugcheck]

      Ugh....its the same water pump being used when fed from a hose.  Granted your not experiencing the RPM's a run on the lake would allow.   In the end, its something that feeds all cylinders, not just one or two.  If the intake and exhaust manifolds have been properly pressure tested, and found no leaks, then where is it coming from?  Ingestion usually is on the intake stroke, but I just don't know what water jackets surround intake passages, certainly no gaskets that I can think of.  It was determined that no water is entering the oil right?  Now if I remember my 140 correctly, there is a water line from impellor/outdrive that feeds into the water pump mounted on the front of the engine.  Is it possible to disconnect this line, hook the hose directly, pull all four plugs, then run the hose without the engine running.  Water should circulate and exit out the prop.   It wont open the thermostat, but if you getting water in the cylinders then it might help with the diagnosis? 

[Neutron68]

General invitation: 
If anyone wants to come join me in Paynesville with their detective hat and toolkit, you are welcome! 
The cabin has 3 bedrooms, hot water, indoor bathroom with shower, full kitchen and a fridge for beverages!!

Eric

[Neutron68]

It was determined that no water is entering the oil right?

Saturday, the next day (about 18-20 hours after it first hydro-locked) I sucked out the engine oil and saw no evidence of water.  I don't know if 18-20 hours is enough time for the oil and water to separate?  Maybe I waited too long and invalidated my observation?
Sunday, the following day, I accounted the events of running the boat around our lake bay and then looking at oil, etc.  This is from page 2 of this thread.

I put new oil in and started the engine and ran it for 10 minutes.  I docked it.  Milky oil.  Crap.

I tried to restart it...hydro-locked again.

I pulled the plugs out and every one had a drop of water in the spark gap.  I ran the starter - a fountain of rhythmic sprays.  There didn't seem to be an end to the water.  As long as I cranked the starter, there seemed to be more water spraying out.

The first time it hydro-locked, I thought I saw a single puff of smoke when we heard the CLUNK.  Could that have been the head gasket blowing out?

With milky engine oil in addition to the constant supply of water in the cylinders, I wonder if this is fixable for less than the cost of another engine?

Eric

[Plugcheck]

      So there is water getting into the oil?  I was under the assumption that everything was fine when testing in the driveway.   Time wise, oil and water separate quite quickly.  The milky look is enough to determine that contamination has occurred.  If water is getting in, then yes, a crack or bad head gasket could be the culprit.  A leak down test will help confirm which has occurred, or worse case, an engine tear down.

[Neutron68]

      So there is water getting into the oil?  I was under the assumption that everything was fine when testing in the driveway.

Unfortunately, Dan kinda stopped looking at details after it seemed to run and restart just fine in his driveway.  He didn't pull plugs and run the starter to be SURE there was not water in the cylinders, and he didn't mention checking the oil either.  Other than the compression test and verifying that the exhaust manifold and exhaust elbows were ok, I didn't get a lot of root cause information from the time he spent with the engine.

A leak down test will help confirm which has occurred, or worse case, an engine tear down.

Dan didn't perform a leak down test.  I'm seeing that you need special guages to perform the test, which I don't have.  If it's going to give more useful information that the compression test, can you find an acceptable guage on Amazon.com and let me know which one?  I can then order one and have it by the weekend.

Like this?
https://www.amazon.com/8milelake-Engine-Cylinder-Leakdown-Diagnostic/dp/B01797HACC/ref=sr_1_15?ie=UTF8&qid=1473865503&sr=8-15&keywords=Cylinder+Leak-Down+Test

Eric

[Plugcheck]

     That one will work, but you do need an air supply to power it.   Most generally 100psi, and really not much volume at all, so a small pancake compressor would suffice.   The idea is that it injects air through an orifice, if no leaks are present then the device shows no leakage.  If a cylinder is on the compression stroke(where it should be) during testing, and is shown to be leaking, then listening for an air leak in the carb indicates bad intake valve, oil fill indicates air leaking past rings into crankcase, etc.    It is far more exacting that a compression test.    Lots of other places sell them including rock auto(online), most auto supply outlets, and tool shops.   Check the oil again, water in it will ruin things quickly.  Things are quickly pointing to a disassembly over the winter, but while its still somewhat nice out, I would spend some time and track down the issue.  Draw a quart of oil off to check.  If no water, test on the hose again, let it warm up, rev up a few times, re start, repeat.    If everything is OK, no water in oil, restarts when hot, no water in cylinders, then try a lake test, especially if a neighbor is available to go out with you.  Let us know what ya find.