Yamaha motor problems

[Guest]

There is someone here who always has the right answer so I thought I would give this one a try. Recently, my motor (1999 Yamaha 150HP Vmax, OX 66)has not been working right. The problem has been going on for a month now. I have it scheduled to go in next week finally!! Here is the problem:

When driving the boat the motor seems to miss occasionally. Like it is not getting the gas it needs. The top end speed of the boat is off about 8MPH from normal. Sometimes is runs just fine and sometimes it is very inconsistant..Fast..slow..fast..slow like it is chugging or something. Makes for a very jerky ride and before I take it in I thought I would give the brains here a chance to figure out the problem. I have my suspicions but I am looking for some second opinions. I think I have ruled out an air leak in the gas line, checked that out already. Your thoughts??ScottS

[Surface Tension]

http://fishingminnesota.com/ubb/Forum43/HTML/000661.html

[Guest]

Thanks guys! The mechanic told me to change the plugs and treat the gas this AM. So, that is what I am doing this afternoon. They keep giving me things to try before I bring it in. They are so busy this time of year, I think they actually hope I can get it fixed. Since I am trying things, anything else I should try. I will start with the gas and plugs.ScottS

[Guest]

My boat sat at the shop for 2 weeks because of incorrect part orders, too busy, etc..

If you bring it in now, you might not have it ready for Minnewaska!

Hope you can figure it out, Scott. That is a complicated motor and might need a diagnostics w/ computer? Only Yamaha knows how many computers are in the motors these days. It sounds like a sensor problem, kinda runs EXACTLY like my car right about now and it needs a new sensor to the EFI system.... Sea Foam worked a little bit in my car! Give it a try.

[Guest]

Scott, did you change oil brands or run a different brand oil through it.

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[Gordon Fothergill]

Scott,

I once had an under floor fuel line deteriorate and cause the same type of problem (it would partially collapse). Just a thought.

Good Luck

[Guest]

There is someone here who always has the right answer so I thought I would give this one a try. Recently, my motor (1999 Yamaha 150HP Vmax, OX 66)has not been working right. The problem has been going on for a month now. I have it scheduled to go in next week finally!! Here is the problem:

When driving the boat the motor seems to miss occasionally. Like it is not getting the gas it needs. The top end speed of the boat is off about 8MPH from normal. Sometimes is runs just fine and sometimes it is very inconsistant..Fast..slow..fast..slow like it is chugging or something. Makes for a very jerky ride and before I take it in I thought I would give the brains here a chance to figure out the problem. I have my suspicions but I am looking for some second opinions. I think I have ruled out an air leak in the gas line, checked that out already. Your thoughts??ScottS

[Guest]

I got it figured out last night. I changed the 6 Spark plugs, treated the fuel with 2+4 and changed the fuel filter. Not sure which one did it, maybe a combination of all of them.

D-Man, I only us Yamalube in the engine so I don't think that was the problem. They say you can use any oil but I stick with Yamalube.

Thanks for the advice from everyone, you were all right. Much appreciated.ScottS