yamaha 150txr idle problem

Flash51 · Nov 18, 2012

My 2005 yamaha 150xtr started running rough at idle. It stalls soon after putting it in gear. After starting it cold, I imediately pulled the cover to take a look and found exhaust smoke inside the engine area. As the motor warmed up, the idle seemed to return to normal but as soon as I replace the cover, the idle drops. It appears I'm getting exhaust up in the engine area depriving it of oxygen. It runs fine each time I remove the cover. The cover is not pinching fuel lines or interfering with anything else. Where can this be coming from? Thanks, Flash51.

kmarine · Nov 18, 2012

Re: yamaha 150txr idle problem

I am not a yamaha expert, but it seem to me like a reed valve issue. Do you have a carb that seem to backfire at idle?

Flash51 · Nov 18, 2012

Re: yamaha 150txr idle problem

kmarine said:
I am not a yamaha expert, but it seem to me like a reed valve issue. Do you have a carb that seem to backfire at idle?

No problems with the carbs. The smoke appears to be coming from the rear of the engine housing at the left rear section of the housing. I can feel the exhuast if I put my hand down there while running. It seems to be leaking from the midsection somehow getting into the engine compartment. This motor only has 170 hrs. on it and it runs fine otherwise. Thanks for your input.

99yam40 · Nov 18, 2012

Re: yamaha 150txr idle problem

gasket or corrosion

Maybe both

Probably need to pull power head and see

Flash51 · Nov 18, 2012

Re: yamaha 150txr idle problem

Thanks. I'm thinking now it's the exhaust gasket at the base of the power head. Don't know why I didn't think of that. The boat needs the bottom touched up anyway. Thanks for your reply.

Capt Ken · Nov 18, 2012

Re: yamaha 150txr idle problem

Gaskets don't usually blow out. Expect a corrosion problem and if there is, good luck getting the power head bolts out.

Flash51 · Nov 19, 2012

Re: yamaha 150txr idle problem

Capt Ken said:
Gaskets don't usually blow out. Expect a corrosion problem and if there is, good luck getting the power head bolts out.

Thanks. I found some corrosion today and was able to poke a hole into the midsection. I can't believe it as this motor is only 6 yrs. old and has been meticulously cared for. Oh well. Thanks again.

erniefish · Nov 19, 2012

Re: yamaha 150txr idle problem

remember, if you have to destroy bolts to remove power head, with that much corrosion they will only come out going up, there seems to be a taper plus all that crud, good luck ,i have the same motor

Flash51 · Nov 20, 2012

Re: yamaha 150txr idle problem

erniefish said:
remember, if you have to destroy bolts to remove power head, with that much corrosion they will only come out going up, there seems to be a taper plus all that crud, good luck ,i have the same motor

Thanks for your input. I'll keep that in mind when I tear into this project.

livebaitdrifter · Nov 24, 2012

Re: yamaha 150txr idle problem

If you get the powerhead off look for corrosion around the drainback orifice mid block in front of exhaust passages. I don't know what year it is but late 80,s and early 90,s 225 hp had massive corrosion around this push in orifice. I had to have area welded and decked, then I rebuilt the motor. I did this on 2 motors the second I welded the drainback closed.

Flash51 · Nov 25, 2012

Re: yamaha 150txr idle problem

Actually, after removing some cowling I found a 5/8" hole in the top of the mid section exposing the exhaust chamber. A friend is checking into warranty repair for me and til then I will screw an aluminum plate with some sealant over this area to get me back on the water. The motor is almost spotless and only 170 hrs. on it. It appears to be a casting flaw.

yamaha 150txr idle problem

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