Fouling Plugs - Cause

[Skeeter50]

Can someone provide me a laundry list of items that would cause plugs to foul after 30 minutes of use on a 89 Yamaha 50HP (Pro 50) oil injected engine?

So far I have only replaced the fuel line between the portable tank and engine and ran Seafoam through the engine (16oz to 2 gallons). Losing power out of the hole. Cranks and idles great, but lose power when I push the throttle forward.

Personally, I don't think the plugs look that bad when I remove them, but a new set temporarily fixes the problem, so I am assuming they must be fouled. Is this assumption valid?

I need to start going through this list one at a time (least expensive to most expensive).

Thanks,

[jb123]

Likely your fuel pump....do you see unspent gas out of the exhaust?
Also, consider not using a quick disconnect on your motor as air leaks can be a pain to troubleshoot.

[Skeeter50]

I've look at the plugs several times and I can say I thought there was a little more oil on them than I expected.