Fouled Plugs

[Fab1]

Hello,I own a yamaha 30hpcv 2cyl outboard that starts to hesitate/stumble ending up fouling the plugs 10 min after driving at slow/moderate revs,i always use premium fuel mixed at 100:1 but iv,e notice when i give it more throttle it seams to clear up but returns at lower revs.I,ve put in new plugs as recommended in owners manual but the problem continues,maybe it is a carby issue,if so how do i ajust it?

any advice would be appreciated.

[Geoff]

Has the problem just started to occur & become progressivly worse or been a problem for some time.

Are both plugs the same or is the bottom one wetter than the top??

If that's the case then it could be the fuel pump diafram is cracked or has a hole allowing fuel to be sucked into the cylinder.

If the diafram then what your seeing is the engine flooding not excess oil.

They are not expensive & easy to replace.

Geoff

[Fab1]

Both plugs are wet the same,and it,s been happening since new.Bought bmt package march 2011.Could the diaphram be faulty since new?

[BFB]

I had a similar problem with a motor years ago. It turned out then that the "black box" for the ignition system was causing the problem. Check to see if spark is strong at low revs.

Not having the right heat range plugs could also be causing the same type of problem.

[tareeterror]

Both plugs are wet the same,and it,s been happening since new.Bought bmt package march 2011.Could the diaphram be faulty since new?

Any warranty? if so, dont fiddle, just take it back.

[Geoff]

Could the diaphram be faulty since new?

It's possible.

To check , remove the fuel pump , dismantle & hold the diaphram up to the

light (sun). If faulty , you will see light through the diaphram.

Geoff