Spark Plug Issues

[amkulic]

Hi,

I'm just looking for anyones advice regarding my 15hp mariner outboard motor

I have recently bought it second hand and bought new spark plugs for it as well

However when I've taken it out recently the spark plugs keep getting clogged with oil causing it to run on only one cylinder and then the boat goes really slow. But when I clean them up it seems to go ok again

Any one got any ideas on what the problem might be or how to fix it ?

Cheers

Andrew

[Dreamtime]

What mixture are you running? (fuel to oil ratio)

Is the gap set correctly (using feeler gauges)

Are they the plugs recommended by the manufacturer? (what number are they?)

Have you checked the mixture adjustment, or is it a new model without the adjusting screw?

[amkulic]

The gap has been left as it was when new

The spark plugs are equivalent to the ones that came out of it

The fuel oil mix could have something to do with it but it is only the bottom cyclinder that is clogging up

I was running it 30-40:1

thanks

Edited August 27, 2008 by fish hunter 181

[dangles]

check the compresiion on both cylinders to see if they're even. A cylinder down on comp won't fire correctly, which in turn wont get the combustion temps up to burn the crap off the plug.

[BlacknBlue]

was it running okay when you got it?- as mentioned, try new fuel at correct ratio 50:1 with proper outboard TCW-3 oil and make sure the plugs are correct for the engine- (internet or local friendly boatshop)

regards wayne

[pelican]

What model and year?

possibilities.

float stuck in lower carby .

twins lower cylinder run rich when the fuel pump diaphram has hole in it

Choke on lower carb not turning off - check butterfly and also linkages as they fall off one carby now and then.

Check it still hs a thermostat in it.

Carby out of adjustment - check linkages

Stuffed HT lead of plug boot allowing spark to earth elsewhere

Check they are right plugs and compression as above.

Edited August 29, 2008 by pelican

[pro fisher]

all the above would probably be your last resort possibilities to avoid having to take everything apart.

check the simple things first.

it sounds to me that it could just be your high concentration of oil to fuel mix causing one of your plugs to clog up, why not both i'm not sure. could be one of other guys' ideas above as to why...

another option could be that as a result of trauling, ie. low revs on the motor, then if it's a 2 stroke that could be your cause as two strokes run best when reving fairly high. so if you were trauling for a while then a bit of oil could have not burnt and staying on the plug.

30:1 is fairly rich seeing as the recommended ratio is 50:1 so i'd say give the plug a clen in white spirits, chech the obvious things, whack the plugs back in and try a leaner fuel mix. unless of course you think continuing to run it is not a healthy option for your engine.

goodluck champ.

[a boat]

Hi Andrew, if your outboard is mechanically sound, that is, it has good compression and spark then the following will apply. Run a fuel:oil mixture of 50:1 and ideally a good quality oil like XD-50. make sure you have the right spark plugs in particular the heat range is correct. Depening on the model the plugs will be different but, if a late model engine they run NGK BP8HS-15. The most important thing for any brand of outboard is that the thermostat is there and working correctly. Any engine, whether it is dirty or clean needs a thermostat for the engine to reach operating temp escpecially at idle.

Your engine with the right plugs, correct oil, ratio and a thermostat will idel fine without fouling plugs.

Cheers,

Huey.