1973 50hp Evinrude issues

couch702

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Jan 23, 2016
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My 50hp Evinrude outboard is acting weird. With motor flushers on and running water through the motor, it starts right up and runs like a champ. Today I took it out on the lake and after I got out of the no wake zone I moved the throttle up a bit and it started to rev up then it shut off. Then the motor would not run anymore. If I got it to start it would not idle for more than a second. I could not get it to run at all. No matter the choke position, throttle position. It would not start and run.
Long story short, I got home and hooked up the motor flusher and the thing started right up and ran like a champ again.
So my question is would there be anything different about it running in water as opposed to through flussers that would cause it to not run it the lake?
 

ondarvr

Supreme Mariner
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Apr 6, 2005
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How it runs on a hose doesn't mean much, it can run terrible and seem OK on the hose.
 

Bosunsmate

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Apr 7, 2012
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Theres no back pressure on the engine on a hose so it will run on one cylinder.
Try a drop test on both cylinders if that shows both cylinders are firing then do a compression test
 

F_R

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Or do the compression test first. No sense in messing with a dead horse.
 

couch702

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Jan 23, 2016
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OK, my next question then would be how do you do a compression test on it? Sorry guys Im new to the water.
 

Leastbay

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Jan 26, 2016
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I posted the same thread the other day on my 25 hp. My compression gauge just came in. I hope to test it today or tomorrow. Bought the gauge for $22 on Amazon.
 

couch702

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Jan 23, 2016
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OK so I did the test. Both checked out at 125 psi. That seems good to me. Any advice on where to proceed.
 

couch702

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Jan 23, 2016
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Update.... I put the motor in a drum of water to simulate the lake and do some troubleshooting.
The only way I could keep it running was by holding the linkage on the carb. I could not get it to idle normal.

When I got it to idle it would slowly start to die.
When I got it to idle again I would try to rev it up via the throttle and as soon as the rpm started to go up it would die.

I could only keep it running by manually holding the throttle open on the carb.

Help please.
 

Michawilden

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Apr 4, 2015
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146
I think you need to clean the carbs. If you can't rev it up but it just stalls chances are that the main jets are clogged. However. It can be many other things. I'd start by doing a cylinder drop test while running on the muffs. Start the engine and then pull a spark plug cap. If your RPM decreases, you have spark on this cylinder. Do the same for the other cylinder. If the RPM also decreases all is well withe the spark. If you pull one plug and your RPM does not change you propably miss spark on this plug. With spark on 1 cylinder the engine can still idle (especially on the muffs)
If you cant get it to start your pull your plugs and check for spark. Should be bright blue. Keep us posted, together we will get you going in no time!
 

couch702

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Jan 23, 2016
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I think you need to clean the carbs. If you can't rev it up but it just stalls chances are that the main jets are clogged. However. It can be many other things. I'd start by doing a cylinder drop test while running on the muffs. Start the engine and then pull a spark plug cap. If your RPM decreases, you have spark on this cylinder. Do the same for the other cylinder. If the RPM also decreases all is well withe the spark. If you pull one plug and your RPM does not change you propably miss spark on this plug. With spark on 1 cylinder the engine can still idle (especially on the muffs)
If you cant get it to start your pull your plugs and check for spark. Should be bright blue. Keep us posted, together we will get you going in no time!

I give that a shot today.
However, I CAN get it to rev up if I do in manually at the carb, just not from the helm via throttle lever.
 

flyingscott

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Apr 8, 2014
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Do a cylinder drop test take a plastic pliers and pull the spark plug wires off one at a time and see what happens. Let us know
 

oldboat1

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9,598
^^agree. Add that you need to get an adjustable spark tester (pretty cheap at your local auto store). Test the spark.
 

Michawilden

Petty Officer 2nd Class
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Apr 4, 2015
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So, you got the drop in rmp while pulling a plug? You can now conclude that you have spark on both cylinders and get fuel to both of them. However, fuel can be delivered through the main jet and the idle jet. With no exhaust back pressure or load the engine could run on only the idle jet. But under load it would fail. I think it is time to pull the carbs off and clean them out. If I do not know the history of the engine a carb clean is always part of my tune-up. Try to pull the carbs horizontal from the engine block so no gasoline will spill. Check the gasoline inside the carb for water. You would not be the first one to fill an already contaminated tank.
Clean out all passages in the carbs and remove the main jets and check of you can see trough them. Remove the mixture screws and blow compressed air trough these passages. You can use carb cleaner. ( I dont use it because in Europe we don't have the same products as the USA) Please post pictures.
 

Faztbullet

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Mar 2, 2008
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These models are bad about air leaks at crankcase halfs and low crankcase pressure. They can have great compression and skirts worn out on piston...a compression test just tells you cylinder can support combustion nothing about motor condition.
 

couch702

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Jan 23, 2016
Messages
18
I'm gonna pull the carb today and clean it out. I hoping that's the problem and its not a timing issue.
 

oldboat1

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However, I CAN get it to rev up if I do in manually at the carb, just not from the helm via throttle lever.

kind of a curious note, there. Do you use the remote only on the lake, or try it when using a flusher? That is, you may have a problem with the remote linkage -- unclear from your description. Throttle operation should be the same either at the motor or using the controls, both in the water and on the flusher.

Incidentally, should not be revving the motor on a flusher, other than a quick spurt to see if it is throttling up.

(carb cleaning is a good idea -- fully disassemble and clean.)
 
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