1982 Merc 50 hp 2 stroke starts for a few seconds then dies.

planerie

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Mar 21, 2018
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Ok... I just purchased an older boat with a 1982 Mercury 50HP 4 cyl 2 stroke. When I first got it I had no spark so I replaced the stator. Now I have spark, it cranks for for about 3 seconds then dies. I have to choke and throttle it all the way up for it to actually crank. It cranks revs (smokes a lot) and then dies. It will crank and do the same thing over and over every time I crank it this way. I did have an issue with losing prime but I fixed a few spots that leaked fuel and was sucking in a little air. Even after fixing those leaks it still does the same thing. The person I bought the boat from told me they had just cleaned the carbs but I took them off anyway and checked them. They do look to be cleaned and the diagrams and gaskets all look new. I am at a loss so was hoping if someone can point me in the right direction. I am no mechanic but I can pretty much fix anything if I can just get pointed in the right direction. Thanks in advance for any help you guys can give me.

Thanks,

Preston
 

Chinewalker

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Definitely sounds like a fuel issue. 1982 should still have a choke - can you confirm that the choke is actually working and the flaps are closing over the carbs? Is throttle linkage operating properly, .ie when you move the warm-up lever, the timing advances and the carbs open up a bit?

Also, what are your compression numbers? Always a good thing to have those in hand so you avoid chasing your tail.
 

racerone

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Perhaps open the lowspeed mixture screws 1/2 turn and test again.------Has the water pump impeller been replaced.---That is not related to the problem but it must be done.
 

planerie

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Yes I have verified that the choke is working and the throttle arm and carbs open when I move the warm up lever. It will only crank when the choke (push key in before starting) is engaged and the warm up arm is pushed all the way up. Now I can keep it running for about 10 or more seconds by pumping the warm up arm up and down after it starts but it still smokes a lot and then dies.
 

racerone

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There is no purpose in pumping the warm up lever as there are no accelerator pumps in those carburetors !!----Keep key pushed in while cranking and push it in as needed till motor warms a bit.
 

planerie

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There is no purpose in pumping the warm up lever as there are no accelerator pumps in those carburetors !!----Keep key pushed in while cranking and push it in as needed till motor warms a bit.

Well if I move the warm up lever back and forth it will stay running for 10-15 seconds compared to just having it wide open and it running for 3. If I dont have it choked or the warm up lever all the way open it wont even crank just acts like it will and sputters.
 

Mohawkmtrs

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What racerone is saying is keep the warm up lever up and don't touch it. Then push the key in exactly as he explains it.

Try it...it works.

As the engine gradually warms up, gradually lower the fast idle (warm up) lever
 
Last edited:

planerie

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What racerone is saying is keep the warm up lever up and don't touch it. Then push the key in exactly as he explains it.

Try it...it works.

As the engine gradually warms up, gradually lower the fast idle (warm up) lever

Ok let me see if I can explain it better. If I put the warm up lever all the way up it cranks...runs for about 3 seconds at HIGH rpms then dies. If you move it lower rpms and back to high rpms it will stay running a little longer but still dies.
 

planerie

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I am just trying to get a clear idea of what you mean. You are saying put the warm up lever all the way up and then push key in (choke) and then try to crank? Then leave it run at max RPMs and just push the key in if it wants to stall?
 

racerone

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You should not let it run at very fast idle !!-----Yes the starting procedure outlined is correct.---Key is to be pushed in while cranking it over.---Pushed in if it wants to stall once it is running.-----If that does not work there is something wrong with the motor.----Note----Many folks have learned how to start / operate an outboard the hard way.----And that way is through an empty wallet !
 

planerie

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Mar 21, 2018
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I had someone at work mention air flow. Do you think if the cowl was clogged could cause it to run this way? I will be going work on it this afternoon and tomorrow but I was just wondering if there was no airflow if it would run a few seconds and die like its doing.
 

racerone

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?---So test with the cowling off.-----And the motor is 35 years old so there are no design flaws with the cowling.
 

planerie

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Mar 21, 2018
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Ok made some progress this weekend. I was able to get the wiring harness back in and hooked all up Friday. I went ahead and tested the compression and all 4 cyl's are 98 to 100 psi. I did what you said as far as closing the low idle jets to closed then opened 1 1/2 turn. I cranked it and it is now running with just a tad throttle and will run for a little longer at idle but then sputters and dies. It will run as long as I leave the throttle up just a hair and seems to run smooth. Now I think I am still losing some prime because after I let it run for around 30 seconds the bulb and fuel hose gets soft. I found someone in my area that said he will check the for fuel (air) leaks in my system and adjust the carbs for $65 so I will probably end up doing that instead of pulling my hair out.
 
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