Mercury Outboard Float / Fuel problem?

[Tim Good]

My outboard seems to have a problem whereby it struggles to start and when it does I need to keep it at high revs. If I get it started I can use it but only fairly fast about half throttle or more. Occaisionally the fuel chamber over flows and pipe on the top of the carb pours some fuel out.

I assume the float is sticking or not closing the needle properly but when I've stripped it down then all looks fine. I've cleaned it all out and still seems to be the same.

Any suggestions?

 

[PeteCooper]

Float height adjustment?

 

[thinwater]

Clearly the float is hanging up or the needle is jamming. Probably just a good cleaning. Take off the carb, remove the bowl, and spray like crazy, being sure to let the needle drop. There is probably no need to disassemble farther. Since the bowl is overflowing, it is not a jet that is clogged, but dirt right on the outside of the float or needle. Easy fix.

Most likely some water go in with the fuel, causing some corrosion and perhaps some emulsion. The cure is to make certain the cap and vent is closed when not actually in use, and to use a good anti-corrosion additive, like Mer Stor-n-start. These additives have been tested by both PBO (I think) and Practical Sailor (I did the testing)--some really work, some are snake oil. If avaialbe in the UK, Biobor EB was the best in testing.

 

[Dave95979]

I had one that leaked fuel into the carb intake it turns out to be the bowl gasket where the 2 rings are

 

[RichardS]

Unless you've altered the float height, which can be usually be checked using the heights detailed in the manual, you must have a leaking needle valve.

Clean the point on the needle and the seat part of the jet with alcohol or whatever, then reassemble the float chamber (doesn't have to be tight) then invert the carb whilst sucking on the inlet pipe (attach a short piece of flexible pipe if needed) as soon as the needle closes you should feel a vacuum being drawn. Stick the end of your tongue over the pipe and you should be able to turn the carb back the right way up and sit there for minutes/hours with your tongue being held tight against the inlet by the vacuum.

If you can't draw or hold the vacuum then the needle or seat are still dirty or damaged and you need to replace them.

Richard