During the summer I used my bass boat to pull skiers, thats when my problem began. This is a 1990 150 Johnson GT. First I started fouling plugs. I thought I might be getting to much oil so I disconnected my oil injection and pre mixed the oil. The warning beeper had been going off so I disconnected it too. Now with pre mixed oil I thought my problems would be over. But plugs still fouled and my feul ball would suck closed. I could open the gas tank and it would pump back up. But it would do it over and over so I could not run it. I did check the vent to the gas tank and there were no obstructions. I also checked the check valve in the pick up tube and it was not sticking. I had a boat mechanic tell me today that I should of never bypassed the oil injection systm and I probably need a new oil pump. By bypassing the oil injecter it was making the feul ball suck closed. Please help. I would like to continue pre mixing to advoid buying a $400.00 oil pump right now.