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Mercury 20 HP issues!!

7K views 15 replies 5 participants last post by  Mark D 
#1 ·
Hello everyone!! I have a 20 HP Mercury that is giving me a. It of a problem. It’s all I can do to pull the starter rope with the plugs in. When I take them out I can pull the rope with two fingers. I haven’t used the motor in a few years and it’s been I’m my basement. I have a little knowledge with marine motors but not enough to know where to start. It would be greatly appreciated if someone could point me in the right direction!! Thank you for your help!!
 
#5 ·
My 20 is a 2 stroke, the shifter is on the side of the motor. It kind of acts like the exhaust valve isn’t opening up to let the pressure out, if I were guessing but I don’t know enough about these motors to say if something like this is possible.
 
#8 ·
I don’t know how many hours it has on it. It ran great the last time I used it. No issues with pull starting it at that time. It has been setting in my basement for a few years and I would pull the rope occasionally to keep it from freezing up. I have shot so WD in both cylinders but haven’t set it with the plugs facing up to let it soak.
I want to thank you guys for your hello so far!!!
 
#7 · (Edited)
Assuming they still use reed valves it is possible one broke not allowing compression to escape but being it has been in storage for years I would suspect and hope it is just stuck, you may try tilting the motor where the sparkplugs are pointing straight up, remove them, bring one piston to TDC and fill the other cylinder with penetrating oil and let it set for a couple days, if that cures it good if not fill the other cylinder and let it set.
If that fails and no one else has a better idea, and if my memory serves me well removing the power head on a Merc. 2 stroke is not overly complex if it comes to that. I have not checked U-tube to see if there are tutorials on it but would be surprised if there are not. Good luck with it and let us know how it is coming.
 
#13 ·
My problem is, I can't pull it hard enough to get it to start. Its super hard to pull with the plugs in and easy when I take them out. When I pull it the rope with the plugs in i can only pull it out like 8 to 10 inches then stops then 8 to 0 inches more until I have all the rope pulled out. If I pull on it any harder I'm afraid I will break the pull rope. Like I said earlier its as if a valve might not be opening releasing the pressure. I will try what you guys have suggested and see if anything helps. Thank you guys very much for your advise!!!
 
#11 ·
It's only my opinion but there are much better penetrating oils than WD45, it is great for some applications but in my experience Kroil Penetrating Oil just penetrates better. I went and checked U-tube, lots of help for you there from diagnosing reed valve problems to fixing bad ones. Good Luck.
 
#12 ·
It's only my opinion but there are much better penetrating oils than WD45, it is great for some applications but in my experience Kroil Penetrating Oil just penetrates better. I went and checked U-tube, lots of help for you there from diagnosing reed valve problems to fixing bad ones. To add a little stress to your situation, Joe and I share different opinions, I would not try to start a two stroke if I thought the reed was stuck, if it is stuck and doesn't turn loose on start up something has to give, with any luck at all if it is only stuck you will be able to get it free and not have to tear into it. Of course Joe may be right and I wrong, starting her up may break it loose. Good Luck.
 
#14 ·
My Dad used a electric motor to crank our lawn mower when I was a boy. He put a belt on the recoil start grove and around a pulley on a electric motor. When it crank he loosened the belt and it jumped off. A outboard may do the same way but I would have a stick to lift it up and don't let it get me.
 
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