Just recently bought a boat with a 2003 Yamaha 200hp 0x 66 saltwater series .Ran it twice before problems arise.While going at wot the motor started surging high to low rpm and smoking excessively .I was able to even it out at low rpm and nurse it back to the marina.Read the forums and replaced the vst filter, high pressure fuel pump filter "which was plugged" .The original owner had the low pressure fuel pumps and vst filter cleaned in June. So i guess I inherited someone else s headache.I took a fuel pressure reading of 35psi at idle.One other thing to mention I replaced the o2 sensor and tube.They were both plugged solid with oil oozing out of orifice.All spark plugs were laden with oil so I changed them.I check the oil linkage and i used a feeler gauge to the engine specs it was OK.There was also an issue with the oil alarm going off because reservoir tank was low.Had a mechanic look at it and he flushed the tank and added new oil.Also he check the gas line and screen going into tank and changed the primer bulb"all with out using any test instruments"?I was told I was getting good gas flow to motor.The only thing I did when I got this boat was start using ring free and putting Yamalube in oil tank and get gas at the marina.I don't think the previous owner used ring free or Yamalube and only used the boat very little,it has 200Hrs on motor.Another observation I made with this motor is that at when I adjust the trim on the motor like around 4 the motor smokes less,trim it down and it smokes more?Any other suggestions would be appreciated.
