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Years of work, engine won't run. Running out of options and about ready to sell.

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kippstakes

Member
72 Evinrude 50hp Lark, 50273c

I've been working on the damned engine for years and it just refuses to run right (or maybe I refuse to fix it right, anyway..). The previous signs were low power output, poor fuel economy, and intermittent hard starting.
Recently I discovered a crack in the fuel line that was effecting the vacuum. While repairing it, I decided to service the carbs and reed valves, and install new gaskets.
After the work was all done the engine wouldn't start. I managed to get it to crank on by opening the throttle and cranking repeatedly. After that, she seemed to run well, but today when I tried starting it up I couldn't get a pop out of her.


The engine has:
New spark plugs/caps
New head gasket (125 psi on both cyl.)
New power pack- spark is fine
Solid, tested wiring
New fuel pump
No evident leaks from p' head flange
Good fuel & bulb that pumps to rock hard (good vacuum)
Sparkling clean carbs and all new gaskets
Floats adjusted to manual specs- no lower than 1 5/8, no higher than 1 1/8'', from flange to float bottom (I basically set them both in the middle of these figures).. maybe I managed to set them wrong somehow.
Reed valves seem fine. When I removed them a few of the reed petals had bent up a bit so, by lightly tugging them down repeatedly, I managed to get them back flush with the block.
The carbs don't have mixture needles, so that's out of the equation.


.. I just don't get it!


One thing I did notice yesterday was fuel leaking down the inside of the exhaust cover, out at the lower unit vents. I chalked it up to flooding, but could it be an indication of something else?


Also, I removed the spark plugs today and gave it a few cranks with my hand over the plug holes. What I got was white-ish vapor, which I assume is correct; it didn't get my hand wet, but appeared to be vapor. However, the 'puffs' coming from cyl. 1 were noticeably stronger/more forceful than from cyl. 2. This doesn't seem good.


ANY ideas???


Thanks for bearing with me, I know this was a long one.
 
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Spark is fine but will it jump a 7/16 gap on a spark tester? Also has battery been load tested and will it spin that engine the 250/300 rpms it needs crank?
 
Batt is good, fresh off the float and spins the engine like crazy. Will check to see what kind of arc I'm able to get on the plugs. You can use the powerhead as a ground for spark testing right?.. if you're careful.
Thanks
 
Best to use a open-air spark tester from the auto parts store; about $8 then you will know. Holding p-lug next to engine tells you nothing about a spark under compression. Go luck
 
The carbs on my 72 were replaced by a later model set somewhere along the line and have plugs (tightened down screws) and a pre-calibrated brass fitting/hole behind them instead of slow needles.
Ordered an open air tester and will check my gap when it arrives. Then again, it would be nice to know sooner than later- maybe I'll give your method a shot.
Thanks
 
Many years ago I rebuilt a 100hp Mercury O/B and the mechanic advised me that the reed valves are very delicate and be very careful not to bend them or play with them as a suggestion take another look at them you may have to replace them, as I said the mechanic told me to be very careful with them
Cheers
 
kippstakes said:
The carbs on my 72 were replaced by a later model set somewhere along the line and have plugs (tightened down screws) and a pre-calibrated brass fitting/hole behind them instead of slow needles.
Click to expand...

I've been lurking in the background following this thread and the above mention makes me wonder...... That two cylinder design had fixed high speed jets and adjustable slow speed needle valves from its design inception up thru 1976. In 1977, the carburetor was changed to incorporate fixed slow speed jets BUT the hp was increased to 55hp. There was a 50hp manufactured back in 1978 & 1979 but other than that, to my knowledge, that two cylinder design remained around 55hp excepting the later 40hp models.

Do you know exactly what engine those fixed jet carburetors came off of? Is it possible that they could be off of a three cylinder higher hp model?

When you cleaned the carburetor... did you manually clean the high speed jet that's located in the bottom center portion of the float chambers? If not, do so as cleaning solvent just doesn't do that job properly. Also make sure that the off brass center slow speed feed line that runs from the bottom center of the upper body to the top slow speed passageway is clear.

Assuming that the engine would run normally with the installed carburetors if all else was as it should be............

Check the stator under the flywheel (beginning of both the ignition & charging system). There are two large coils that provide approximately 300 AC volts to the powerpack capacitor to energize the powerpack. The coils are located (1) at the extreme front and (1) at the extreme back. The early model stators were not enclosed in any kind of insulation to protect the unit from the heat and those large black coils would fail and melt down within a short time... the later stators were enclosed and insulated. However, both types have been know to crack and fail which resulted in weak, erratic and eventually no spark/ignition. Bottom line.... visually inspect the stator closely!

The spark must be tested with the spark plugs remove in order to obtain the highest rpm possible. The cranking rpm must be 300 rpm or higher in order to have the stator function properly. A spark tester should be used with a gap set to 7/16"... if no tester is available, you could use a #2 philips screwdriver shank stuck into the spark plug boot spring wire connector, then hold the shank of the screwdriver that approximate distace away from the block.

The spark must be a strong blue wide lightning like flame... a real SNAP. Is it?

Spark plugs should be Champion QL77JC4 plugs gapped at either the original setting of .040 or the later (middle 1990's) setting of .030 . One or the other may give improved performance at either top end or idle... it varies from engine to engine.

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1

The "whitish vapor" you say you felt shooting out of the spark plug holes.... Unfortunately, to me, anything whitish spells "water" coming from somewhere.

However, assuming that the whitish stuff is not water and all linkages are as they should be..... If you have compression, proper spark, and fuel, the engine has to run UNLESS the flywheel key has not been torqued properly (105 foot pounds) which caused the flywheel key to shear (out of time). Let us know what you find.
 
THANK YOU for the thorough appraisal, that must have taken some time and it's appreciated.

I'm not sure where the carbs came from, they were on the engine when I bought it. I will check the part number, which I think is stamped on the bottom of the float bowl, when I take them off in the next few days.

I have ordered new reed valves and plan to install them ASAP.

The high speed jets have been cleaned. Carb cleaner and a few white pipe cleaners ran til they came out spotless. I assume the jet you speak of is the horizontal opening at the bottom of the float bowl in line with the drain plug that becomes vertical after about an inch. I also cleaned the vertical brass tube that runs vertically through the carb's main intake, the one with an ID of about a mm.

I am not sure about the condition of the stator. I plan to take the flywheel off to check the key, and will check the stators then. Also, I ordered an open air spark tester a few days ago and will have a conclusive verdict on spark strength soon. The plugs are QL77JC4s.

As I recall, the floats sat almost perfectly horizontal to the flange surface, but I will check them again when I take the carbs off.

I will get to tinkering and post back when I know more.

Thank you again for weighing in!
 
Sounds like you have it pretty well covered. Let us know the condition of the stator... cracked, melting down/dripping, insulated or not.

The imprinted numbers on the carburetors are simply factory run numbers and do not reveal their identification.
 
Tested the spark today and I'm getting a very strong 3/8'' arc, so that's encouraging. Took the carbs off today, cleaned them and reset the floats. I'm still not sure which model engine my carbs are from. I will try to attach a pic. Okay it won't let me.
Anyway, according to the manual, late model carbs have orifice plugs, earlier models have adjustable needle valves- that's as much direction as it gives. It appears that both carb types exist on motors of equal hp, like my 50.. it seems.

New reed valves are coming in the mail, when I get them installed we'll see if she wants to more cooperative. If no, I'll check the timing and make sure the flywheel key's intact.
 
Not sure what the size these are by looking at them. Manual says the 50hp has an idle orifice plug, while the 55 and 60s have intermediate plugs. Not sure how hard this is to spot, but it makes me wonder what effect putting a 55 or 60hp carb on a 50 would have. If the displacement is identical, it shouldn't make a difference, correct? Might even advance its performance a bit?
 
Couldn't find much except for the casting numbers (322292 on the body, 313355 on bowl). I investigated those numbers and found that they tend to be on 55-70hp three cyl. models. If I install the new reed valves and problems persist, then I will start really worrying about carb compatability issues. For now my money's on the reeds.

Also, the plugs seem pretty well fouled. Since I was only able to run at low revs (vacuum leak in the fuel line), this makes sense. New plugs are en route, so that might also make a big difference.
 
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That makes sense. I'll buy a ranged set and experiment a bit, see if that helps.
Thank you for the input.

Also, on an unrelated topic, I'm getting mixed signals on the proper plug gap for this model. I'm running QL77JC4s, and have read that both .03 and .04 are correct. I've also read that .03 generally applies to later models and .04 for earlier Evinrudes, like my 72. However, I have encountered the .03 opinion more often, and applied to all years.
Can anyone clarify?

Thanks
 
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I sure hope he did, because the fast jets are stripped to shreds and not coming out. The actual hole looks unaffected so I guess I'll just have to roll with what I got. Don't think I will need WOT too often anyway, not a ski boat, just for fishing.
 
On a flushette........

A 20" shaft engine = 1000 rpm.
A 25" shaft engine = 1200 rpm.

When in the water, the idle rpm will drop to normal.
 
Okay, took her out today for a test run. Unbelievable- ran worse than it ever has before. After sitting at the dock cranking the engine for about 20 min (intermittently, of course), to my amazement, just as the batt was almost out of juice, the engine popped on- and then proceeded to run like it was being choking to death. I even started it at the house on cuffs immediately before putting in.

I could only get it to idle in the start position or above, but it definitely didn't want to even then. It would run well for a moment and then slowly start to die. Just for kick I decided to try and put her in gear- forget about it- died instantly and that was the last time she ran. I'm wondering if downsizing the idle orifice jets was such a good idea, it seemed to idle much better with the 32s in the water.

It seemed to start fairly easily after I put it back together a few days ago, now it doesn't want to do anything. Am I flooding this thing in some unusual way that I don't realize? Maybe putting it up to trailer tilt is pouring gas from the sump into the carbs? I don't think that's possible, and wasn't a problem before...

The most frustrating thing is that the very few times I dared to take this boat on the water, many months ago, I had no starting problems whatsoever, it just ran like crap and couldn't break 11mph WOT (I'm still not sure if it can do better, though I did repair a leak in the vacuum line since, and am hoping that that was the cause). I can't think of anything I have done since then to cause a hard start issue.

I feel like I'm going insane. I've been working on this thing for YEARS and have never had a peaceful day on the water; just a hole to throw money, time and patience into.

Open to ANY suggestions
 
At this point I think I might just cave and shell out the bucks for a proper 50hp carb, fed up with the one I have now. Seems the 70hp carb on there should work, but that's only in theory, and I'm tired of worrying about it.
 
The bulb does get very hard. It will loosen up a bit after the motor's been cranked a minute, but the engine's probably just using fuel and making room in the bowl for more, yes?
I would be surprised if the floats were sticking, I just had these things apart and they were clean as clean gets.
Had the pump open the other day and everything looked perfect, almost new.
I'll check the plugs tomorrow.
 
Still lurking with nothing more to add except I'd suggest looking around the dealerships and other outboard repair shops for good used carburetors of the proper year/hp that can be cleaned and rebuilt to new condition. If you have the right compression and ignition/spark... this is the only thing left.

Reminds me of a old saying we had of cars of many a yesteryear when they had seen better days...... We would jack up the radiator cap and drive another car under it, lower the cap and drive away.
 
You read my mind. Ordered the correct carbs online, they arrived yesterday. Putting them on tomorrow with fingers crossed.
Thanks again for the help. I'll let you know how it goes, which ought to be well- this motor is running out of excuses.
 
Alright, carbs installed and engine is running stronger than it ever has before. The contrast is pretty stark bt the different carb types, not just in their performance on my engine, but in the way they're engineered.
Anyway, hopefully I can get her out on the water this week and we'll see how it does under load- better I'm sure.

thanks for all the help.
 
MikDee said:
And what was the suggested spark plug gap again?
Click to expand...

Original recommended gap = .040
Revised recommended gap as of the late 1990's = .030

One gap or the other may provide improved performance at either idle or full throttle... varies from engine to engine.
 
joereeves said:
Original recommended gap = .040
Revised recommended gap as of the late 1990's = .030

One gap or the other may provide improved performance at either idle or full throttle... varies from engine to engine.
Click to expand...

Thanks, The O.P. stated .03, or .04, for a spark plug gap earlier in the thread, I was hoping that was a typo?
 
Alright, just got back from first test run with new/correct carbs. She did better but still seems substantially under-powered, making about 18 mph at WOT. Seems a 50hp should push a 15 ft boat a little faster, I was hoping for about 30. Started right up tho, so that's good news. It just doesn't seem to be reaching the RPMs it's capable of.

https://www.youtube.com/watch?v=k9cg1VcVmkE&feature=youtu.be

Something I've also noticed is that the idle seems a little weak- will run strong and slowly fade until stalling. Also, when I popped her in neutral while approaching the dock the engine started to race, which also happened when I had the cuffs on the other day. So basically, I'm getting a dying idle one minute and a racing idle the next, seems strange. My first inclination is toward the fuel pump, which I've checked and rechecked- diaphragm seems strong, maybe I'm missing something.

Ideas? Thanks
 
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