Today my 04 VMAX 150 OX66 started stumbling or hesitating when I would push the throttle up from low RPM. Mainly while accelerating out of the hole.

Has anyone experienced this and what was the solution. I was thinking a dirty fuel filter or fuel pump needs replacing.

Any help would be appreciated.

Thanks

Or a bad Primer Bulb or Fuel Line collapsing?

if it stumbles on take off but then runs good look at the fuel lines for an air leak, clean and or replace the filters.

Put Sea Foam in it.

Pull the O2 sensor and give it a cleaning also.

Thanks guys I was hoping that would be all that it needed was a good cleaning and new filters.

Mike - What can I use to clean the O2 sensor?

How long has it been since you changed the plugs? When mine does this it is usually the plugs. Unless you have re-set the oil pump linkage these motors run rich and the plugs usually foul at 30-50 hours of use. The linkage is set rich at the factory and most of the motors I have seen have never been re-set to the specs Yamaha recommends in the manual. Get some NGK's at NAPA and try this first. I bet it solves your problem.

Steve
www.amistadtackle.com

Guys if you need to replace your O2 sensor you can get them at auto zone for $50 instead of $300 from yamaha i read this in the yamaha motor section of the bbc

I replaced the plugs last April but the boat sat for most of last year because I didnt have time to fish. I dont have that many hours on them.

clean o2 sensor with a stainless steel brush or stainless steel pocket knife, Scrap the carbon off. Also since it set for a year,,,,,,,Gary hit it dead nut...SEA FOAM.

It could be the O2 sensor. As Mike suggests you can clean it. Google Bass and Walleye boats article on cleaning the OX66 O2 sensor and you'll find the info to clean it. If you spent significant time at idle the plugs could still be fouled.

Here is what I posted on removing the O2 sensor.

O2 Sensor

Ok guys I really appreciate all of the input, I have learned a lot.

I run ring free and Stabil in every tank of fuel. I assume that I still need to Sea Foam occasionally (annually) the engine though? Is this correct?

Also for Sea Foam do I need to mix it with a whole tank of gas or just mix a smaller amount.

Thanks again.

I would replace the ring-free with sea foam. I am not a ring-free fan. Seen too many Yamys have pump screen problems while useing Ring-free and no problems while useing Sea Foam.

These are just some things that I do because I've had the same problems you talking about and it come from 1 of 2 things everytime. 1. Bad spark plugs and 2. the spark plugs got bad and fouled up because I was running crappy oil instead of Yamalube. I ran some Penzoil Synthetic through mine once because I was running low and couldn't find the Yamalube. It ended up costing me about $60 in spark plugs and turble performance out of my motor. Changed the plugs, trashed the crappy oil and haven't had an issue since.