Help needed with Mercury 4hp 2 stroke...

[Hoblands]

Outboard motor nightmare!

Just sold my trusty 4hp Mercury on Ebay and the buyer collected it at the weekend with my assurance that it is an excellent runner and last used in May on my tender before being stored indoors.

I now have the motor back and have refunded the buyer as at some point between last being used, flushed through and fuel removed it has developed a fault.

The motor started briefly for the buyer and then cut out and then refused to start again while dripping fuel from the underside of the carb. I have a limited knowledge on outboards but was able to remove the carb and clean it - jets ect look to be in good order. Reinstated the carb and air box and the engine jumped in to life on the 3rd pull of the cord, revved, ticked over and went in to gear without fault. After running for around 10 minutes I shut it off and tried to re-start a few minutes later - nothing, and the carb is flooding again with fuel dripping from the underside...

Any advise gratefully received

Paul

 

[dehlerdave]

Sounds like you've got dirt in the fuel tank. Clean the carb again and then drain the fuel tank and take out the fuel tap. There is a filter on the inside, clean that and refill with clean fuel and you should be ok providing you have cleaned all the jets and the fuel pp.

 

[Hoblands]

Many thanks. I will give that a try tomorrow and post the results

Paul

 

[rbmatthews]

Could also be the needle valve that is supposed to shut off the flow of petrol when the float chamber is full. If the float hinge has been bent while cleaning, it may be that the valve is not closing properly when the float chamber is full and petrol keeps flowing in. It should give the correct height of the float hinge above the edge of the float chamber in the workshop manual for the engine, which you can bend manually to the correct position. On ours it is 3 mm, but it may differ between engines.

Alternatively, the seating on the needle valve itself might be damaged, and you might have to replace the whole needle valve assembly.

 

[VicS]

Almost certainly what has been said.

Needle not shutting properly or float sticking.


Usually the correct adjustment of carb floats is that they just close the needle valve when exactly horizontal/ parallel with the joint between carb body and bowl. Turn upside down to check. Avoid messing with it though unless you are sure you may have bent it previously

Look out for a little spring clip between the float arm and the needle. If its not refitted you could have the opposite problem of valve sticking shut!

Exploded diagrams which might be useful at http://www.boats.net/parts/search/Merc/parts.html


You may find a workshop manual at http://boatinfo.no/lib/library.html# Go to the Mercury section and scroll fully to the right, There are some non OEM manuals there which should cover your engine.

 

[Hoblands]

Thanks for replies - I will take the carb off again and have a look. It seems to be the same problem since I cleaned it as previously though, is it possible for the needle / float to get bent out of shape with just time / wear and tear?

Cheers
Paul

 

[Hoblands]

Thanks for replies - I will take the carb off again and have a look. It seems to be the same problem since I cleaned it as previously though, is it possible for the needle / float to get bent out of shape with just time / wear and tear?

Cheers
Paul

 

[rob2]

Probably not, but it could certainly have got some dust into the jet, whilst draining the fuel or cleaning the internals of the carb.

Rob.