I have a 2003 Ox66 yamaha 3.1 225 with 350 hours. I have gone through 6 mechanical fuel pumps in the last 100 hours (changed all three twice) and now today I find I have one leaking again (the middle one). The other two are fine. I am wondering what is causing this? I have heard the diaprahms on these pumps frequently fail, but am wondering if another problem is causing these failures. The motor runs good, but when a pump goes I lose top end and have to drop the throttle back and then punch it to get it back. Change the pump(s) and it is fine until the next time it happens. This is getting expensive and I would hate to blow the engine if there is another problem causing a lean fuel condition.