1999 OX 66 225 surging

[bigdave]

I have a 1999 Cobia 240 W/A with a 225 OX66. I put it in the water last weekend after running her at my house. She started stalling immediately, then finally idled up and kept running. Once clear of the dock she started to loose power and die unless someone pumped the fuel bulb. I have replaced the fuel filter, fuel bulb, blew out the breather line, cleaned the spark plugs, knocked the ball out of the anti-syphen valve and am now dumping the fuel. The reason I am pumping out the tank is it ran better on a 5 gallon can and I wanted to salvage the fuel if possible. I bought the boat in July at a bargan price knowing it had fuel issues. The man I bought it from hadn't used her in 4 or 5 months. She doesn't knock or make any unusual sounds when running in my driveway. Am I on the right track?

[MeyersHurtado]

I am a newbie to this website.
I hope you guys help me always if I fall in trouble. And I'm really happy to join with you.
Pls share your valuable tips and tricks with me.

[wildonesfl]

Have you looked at O2 Sensor Posts

I have simular problems. Looking at other posts it sounds like the O2 sensor needs to be service regularly. I'm in the process of cleaning mine.

[bigdave]

1999 ox66 225

I figured out the problem last night. I was replacing the fuel line from the anti siphen valve on the tank to the fuel bulb and discovered a fuel water seperator that probally hadn't ever been replaced. The filter was severly rusted with holes along the top which allowed the system to suck air and lose prime. Also fuel comming out of the filter was full of rust and contaminents. I am going to water test the boat tomorrow and I am optomistic.

[bigdave]

I have simular problems. Looking at other posts it sounds like the O2 sensor needs to be service regularly. I'm in the process of cleaning mine.

I cleaned the O2 sensor a week ago, it didn't fix my problem.

[bigdave]

I figured out the problem last night. I was replacing the fuel line from the anti siphen valve on the tank to the fuel bulb and discovered a fuel water seperator that probally hadn't ever been replaced. The filter was severly rusted with holes along the top which allowed the system to suck air and lose prime. Also fuel comming out of the filter was full of rust and contaminents. I am going to water test the boat tomorrow and I am optomistic.

I water tested the boat motor and had poor results. I am going to change the spark plugs tomorrow, then plumb in my new fuel/water seperator, and try to clean the intake with some carb cleaner. If I can't get it going tomorrow, I am putting her in the shop Monday.

[bigdave]

1999 OX 66 225 Surging

I found another problem today. I inspected the fuel lift pumps and noticed all 3 pumps had the diaphrams either torn or cracked. I am replacing them tomorrow and will see if this solves all problems.

[bigdave]

1996 OX66 fuel problem

I ordered new pumps from a dealer so they are under warranty. I haven't replaced them yet, but spoke to a certified yamaha tech yesterday and he believes I should be fine after replacing them. He told me that without the lift pumps working and regulating fuel pressure I woul have poor idle, stalling from too much fuel being dumped into the cylinders and the tendency to flood the engine. My symptoms exactly. I would have just replaced the diaphrams myself, but the cost of 2 diaphrams and gaskets makes it almost more cost effective to buy new pumps. I will let you know how she runs after replacing the pumps.

[bigdave]

1999 OX66 225 fuel problem

After replacing the lift pumps, the fuel bulb is staying hard, engine idles smoothly and there is no fuel being blown out the exhaust. I still need to water test the boat but expect positive results.

[jb123]

usually pumping the ball with bad low pressure pumps will make the engine run worse if the diaphrams are bad, dumping raw fuel into crankcase and not into VST/intake but if they were bad they needed to be replaced anyway.
if this doesnt help i would look at your fuel delivery side,from tank, pickup tube,lines, ball,filters and then clean VST tank and clean/replace filter

[bigdave]

Motor is running great. I encourage anyone that owns a boat to buy a shop manual and follow the troubleshooting guide.