Fuel Vent? Running Rough Merc 200

[fishfetchr]

Hello All- got a question on how to change the vent/overflow piece mounted on the outside of the hull. I am hoping that maybe this is my intermittent problem of the motor having a loss of power & bogging down/shaking a bit between 3000 rpms on up. Can this be checked by simply opening up the main fill cap to see if I can "vent" that way to see if my problem goes away? I wouldn't mind replacing but not really sure how, as when I flip through catalogs showing replacements, it seems to be a 2 or 3 piece device with the vent, backing nut of sorts and a short piece of tubing. Does the exterior piece get grapped and screwed off? Is it done by removing the whole fill? Any help is appreciated. I have replaced the plugs and seperator( and this is actually when it started running badly-right after the plug & seperator change):^- guess I'll also try replacing the primer bulb ( maybe the ethanol is ruining the ball?) I heard the little check valves is the ball can go causing a restriction, The ball remains firm when running. I am trying to do the simple things first that I can tackle. I suppose I can hook up a portable 6 gal. tank to see if the problem is at the motor (are these portables self explanatory as far as hooking up)? Anything you folks recommend to add to fuel to clean out the carbs? Whats this seafoam stuff all about and how's it used? The problem appears to be intermittent, so I hoping its not major. Could it be power/battery related? I have noticed the amps gauge reading around 3/4 instead of in the middle on a few instances too. I cleaned up the terminals, charged the battery on a charger. Could this be a stator issue? The motor is a 1986 200 Merc straight 6 on a 20' Robalo CC
Thanks So Much For Your Time.
Mario

 

[andy6374]

Re: Fuel Vent? Running Rough Merc 200

If your vent was clogged your primer bulb would probably collaspe.

When was the last time you changed the entire fuel line and primer bulb?

Try pumping the primer bulb when the engine boggs, if this saves the engine from falling on its face then it's time for a fuel pump rebuild.

Cleaning the carbs can only be done by taking the carbs off the engine, diassembling, cleaning with carb clean, blowing out with compressed air and reassemble with new gaskets.

Also the antisyphon valve on the tank can cause restrictions, but these too usually leads to a collasped primer bulb

 

[fishfetchr]

Re: Fuel Vent? Running Rough Merc 200

Thanks for the reply Andy. The fuel line & bulb is less than a year old. Do I have an anti-syphon valve? How would I find it and whats that all about? I find it weird that this all happened 1st run after changing the plugs & seperator. I double checked the plugs and wires and all seems OK. Please advise.
Thanks Again.
Mario

 

[andy6374]

Re: Fuel Vent? Running Rough Merc 200

probably coincidental, but bypass the seperator and see if it helps.

Did you try pumping the primer bulb when the engine starts shaking?

Check the little plastic inline filter under the cowling too.

Just to rule it out, make sure you have spark on all cylinders and run a compression test.


If all above checks out I'd look to the carbs.