1977 70hp - Carb rebuild now no power...

I'm having trouble with my motor and I need some advice. A little history, the motor is a 1977 70 hp Evinrude (70773s). I recently installed a new water pump and rebuild the carbs and replaced all of the fuel lines.

I'm experiencing low RPM and lack of power from the motor. According to the new tach (boat never had one before and hopefully this new-used one is correct) it's idling at about 1000 RPM. At 2000 RPM it purrs like a kitten. It accelerates to 3000 RPM with no problem but that is as far as it will go. If I try to go past 3000 it give a little surge then drops back to about 2800 and continues to surge a little.

Here is what I have tried so far:

• Spark: spark is good on all three cylinders, will jump a 1/2 inch gap.
• Compression: reading are 120,115,120, so looks good to me.
• Cylinder drop test (pull plug while running): top and middle very noticable change in engine perfomance, lower carb only small differance...
• timing light on each plug lead: all three had a consistant pattern at idle and the pattern appeared to be the same for all three as well.
• Carbs: dismantled and checked the jets, none were pluged, re-adjusted the floats the middle carb was set a little to high.
• Installed new spark plugs
• Adjusted the linkage
• Fuel is new with marine stabil added

On the muffs it starts up nice and idles fine.

The thing I'm most concerned with is the lack of response from the bottom cylinder when the plug wire is pulled while running. It has compression, spark, the float bowl fills with fuel and the jets have been verified clean and clear, what else could be wrong? Is there any other way to tell if that cylinder is running or being dropped? Last night I pulled the new plugs and compared the bottom one to the other two and they all look pretty much the same, basically clean and dry. So it sounds like the bottom plug is firing or it would be black and oily right?

Your caption is more telling than anything else. Are you saying you did not have this problem before the repairs were made? Gasket for lower carb in place?

The last time the motor was run it did not have this issue. The reason for the rebuild was that the motor sat unused for about 3 years. The gasket for the lower carb is in place, all of the gaskets and floats were replace using OEM kits. After the trial run I took all three carb apart again to verify that there were no blockages and that the gaskets were in place. I know that the float bowl on the lower carb is filling with fuel but I'm not sure how to verify that the fuel is reaching the cylinder?

As I recall, there is a trick regarding that. I believe that you run the engine with the cover off the carbs, and then you partially block each carb in order, and see how that affects the way the engine runs. I believe the theory is that partially blocking the carb makes it draw more fuel and run richer. Hopefully someone who fully understands the procedure will chime in.

And where did you get the work done?

If you do a word search, and put in "finger carb", and go down the list to "3cyl leaking" you will bring up a post from last year that looks just like yours. May be helpful. I would have attached it as a link, but it would have taken me years to figure out how to do that.