Question on reed valves

I have a 84 50 hp Merc .Is it a hard job to change these valves? Is there any way to check or test them before dismatling the engine?Thanks for the help

Re: Question on reed valves

It's not common for these to fail, what makes you think that they're bad?

To change them is not so easy, it requires removing the powerhead and splitting the crankcase halves to gain access to the reed blocks.

Re: Question on reed valves

emckelvy said:

It's not common for these to fail, what makes you think that they're bad?

To change them is not so easy, it requires removing the powerhead and splitting the crankcase halves to gain access to the reed blocks.

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I can't get the 2 top cylinders to fire right. When I remove the wires from #3 and 4 the motor will almost stall .The upper 2 cylinders make hardly any difference the way it runs.I have 120 lbs compression on thesecylinders and the plugs do have gas on them.Thanks

Re: Question on reed valves

Unless it's spitting fuel back out of the top carb, it's not reeds.

If you have good fire on the upper (2) cylinders and fuel, and it still won't run, perhaps there's too much fuel.

Either fuel pump diaphragm or some other issue with the carb flooding out.

Have you verified (by timing light or spark plug firing indicator) that, when the motor's running on #3 & #4, that there is spark on #1 & #2? That is, with spark plugs in those cyls, and the spark plug wires hooked up, do these cyl's actually fire under compression?

Another thing I'd try, just for a lark, is to disconnect/plug the fuel line to the top carb.

Then, make up a spray bottle of 50:1 mix, lite the motor off and spray the mix into the top carb.

If you can get it to run at all this way, the problem would definitely point to the carb.

If it makes no difference, and this motor has external fuel pump(s) you also must eliminate a ruptured diaphragm as a problem, as this'll dump raw fuel into the cyl's and they won't run.

Note that you should run on the spray bottle for just the time it takes to diagnose the problem, as you're getting lube to #1 & #2 only when you spray pre-mix into the carb.

HTH and let us know what the results are............ed