what do reeds in mercury outboard motors do and what problems can they cause when they go bad?

Answer 1

I will be back later to explain reeds correctly and what they do.

If you go to How things work.com they have some good flashes that show how a 2 stk works. A reed valve allows air to be pushed in through the carb or throttle body in to the crank case when the piston is moving from BDC (bottom dead center) to TDC (top dead center) the end of this movement is the secondary compression stroke. This movement also allows the crankcase area to increase and the pressure decreases thus allowing air to be pushed into the crankcase past the reeds. As the prior air/fuel charge is ignited, the expanding nitrogen pushes the piston from TDC to BDC thus creating primary compression of the air fuel mixture in the crankcase. This will then push the air fuel mixture into the cylinder via the intake ports in the cylinder wall. The reed valves must seal the crankcase pressure or the mixture will be pushed back through the intake (carbs) and then "spitting" fuel outward. Reeds are a one way check valve,in a nut shell.
The running issue will vary as the degree of failure. Split or chipped reeds will cause a running issue at higher speeds, not too much a lower speeds. Broken peddle will cause low speed missing and no running at higher speeds. Weak reeds will make a motor run great at low speed but limit the rpms the motor will turn. A damaged reed will not cause a backfire, it can do what is known as a lean pop through the intake.
If you have an Optimax, different running issue, let me know.
To clear something else up, 2 stk motors control the crankcase pressure through, piston port, Reed valves or rotary valves. Reeds can either be plastic or metal.

Answer 2

Mercury Outboard Problems

Answer 3

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Yes, it's rare but it can cause rough idle etc, but the problem you discribe sounds like bigger problems than a lesking crank seal.....Has this enging been "rebuilt? When you say the carb was rebuilt, Did an outboard mechanic rebuild it, and set the float. Can you blow air through all of the ports in the carb, it sure soundslike something is plugged up. When the carb was reinstslled did you use new gaskets. Just for the heck of it, Try starting the engine, and take a can of WD40 and spray around the carb, bolck, fluwheel etc. is if the engine reacts to the spray. Other than that, It sounds like a n old mechanic needs to take a look.. The first thing I'd do past the above is pull the head. Good luck!

Answer 4

Reed valves are flat thin little peaces of metal that that cover intake and exhaust ports in a 2cycle engine. They flex open and closed as the piston runs up and down in side the cylinder sealing on compression stroke and opening on intake and exhaust. They can cause a motor to back fire when they are, cracked, worn, bent; or not to run at all. Rough Idling and such. Controlled by + or - pressures in and behind cylinder.[ Reed Plates and cages]

Answer 5

Reeds act similar to the valves in a 4 cycle engine.
Can cause hard starting, back firing, poor runing

Answer 6

there called reed valves, they actually allow the fuel mixture to come into the cylinder and close during combustion. every 2 cycle motor has them, well unless its a diesel and thats a different story. when they go bad it wont start because it cant pull the fuel mixture into the cylinders. if you can actually pull them out then send me a message and i can tell you how to check them

Answer 7

Check the transfer port lines on the side of the block first. These are rubber 1/8 lines that run from one cylinder to the other, and do deteriorate over time. Cracked and leaking lines will give the same symptoms as a bad crank seal.

Answer 8

hi guys at this point my motor runs well at a Ideal ' up to 1200 rpm's when I throttle down on It the motor dies '
a ace tech told me the carbs need rebuilding ' so I had him do this $ 150.00 took boat to lake'
the very same problem' now he tells me It's the read valves' just who do you believe these days ?? when
a head mechanic tells you It's the carbs and he wrong' I feel Like I been had'
these people been In business over 35 years' I probably should share there name'
at this time' I'm holding back on that'

Answer 9

I'm having similar issues, we think its reeds but will know tomorrow. Symptoms for me are it won't hold an idle. Runs ok under load but the carb is spitting fuel and again, at idle it just dies....

Answer 10

What Are Reeds