Merc 20 2 stroke FIXED!!!!!!!

[wmk0002]

It may help you to buy a knock off tiny tach from Ebay or Amazon. You can get them for about $15. It will help you get it to the factory recommended forward idle speed (in tank or water) plus give you your WOT rpm's just in case you need to re-prop it.

Yes sir, already have one. My idle speed prior to making linkage adjustments was 650-700. I thought it was idling low due to being rich and subsiquently misfiring. But now I think it was misfiring due to the low idle. There was fuel bubbling up from under the water when it would die

Oh, I see. What are the forward idle specs for your motor? I think most magneto ignitions recommend 550-600 rpms while CDI ignitions are approximately 750 rpms. I would think your 650-700 would be fine.

 

[Bowhunter1661]

I believe spec is 700-800. We shall see tomorrow. I get the rest of the parts to get the motor running tomorrow afternoon. Praying this works or else I am buying a four stroke!

 

[Bowhunter1661]

Well here goes nothing. Heading to the river. Just ran it on the muffs and it appears to be running better. Then again, it ran decent on the muffs last time. Wish me luck!

 

[Bowhunter1661]

Well... Just got done at the river. You all are reading a post written by the happiest man in the world right now! First off, the motor fired right up without hesitation. Idled smoother that any merc I have seen. When I would take off and run full throttle then come back down to idle, it would run as smooth as can be! Not one hiccup, missed beat... Nothing. Idle screw is set to 2 turns out from lightly seated. Running slightly rich, but, Boyesen recommends this due to the possibility of lean pops destroying the carbon reeds.

I am not sure wether it was the reed replacement, seal replacement or what. All I know is the motor is running great. I do not even have to mess with the idle knob to get it to run. RPMs are around 1100 at idle and 900 in gear.

MAN AM I RELIEVED!!!!!

 

[perchjerker]

great to hear! your hard work paid off!

I do know the Boyesen reeds are great, I have them in my snowmobiles.

like you said cant be sure what it was, probably a combination of things

 

[Bowhunter1661]

great to hear! your hard work paid off!

I do know the Boyesen reeds are great, I have them in my snowmobiles.

like you said cant be sure what it was, probably a combination of things

Yes sir, Likely a combination. Personally I think the motor was sucking air and running lean. The reed plate has three Phillips screws and two nuts that hold it in place (two screws on bottom, one on top and two nuts in the middle) When I initially disassembled the reed plate the two bottom screws were hardly tight, one may even consider them loose. After disassembling the plate and removing the cage I found the gaskets were soaked all the way through with gas. This probably explains the fuel under the intake. If it was loosing fuel, it was surely sucking air, path of least resistance.

 

[fishdaddy]

Back to the lower crank seal for a bit here, when I ran mine either hooked to a hose or in a garbage can of water I never had water going up the shaft into the lower cylinder and the motor ran fine but when put in the lake it sat deeper in the water and this was when the water fouled the lower cylinder. After the motor stalls pull the bottom plug and check for milky crap on the spark plug, if it's wet with water and oil you have a lower seal issue and yes pulling the power head for this seal is a pain but take your time and pictures along the way and it can be done. Once the power head is off the motor it is a bench job.


Fishdaddy