Yamaha 150 carbed idle issue

Blue_Runner · #1 05-29-2018, 04:35 PM

Ferm/Spare - anybody.
2004 with around ~1200 hours. Runs out perfect at all RPMs except at idle (600 rpms) it runs fine overall, just occassionally coughs, but keeps running except sometimes cuts off. It cut off with me probably 20 times over the course of a day. Seems to be worse when trimmed up. I noticed the primer feels soft and not what I'd expect. Couple of times had to choke motor to start it back (after priming). But if I just increase idle in neutral to say 900, it seems fine?

Right now I'm thinking I'll replace the primer and the small fuel filter under the cowl. Wondering if it could be sucking air and/or restricting flow at idle? What else could it be? Carbs? Reed valve <-- I don't know what that is, lol.

Been a long time since I cleaned the carbs - like probably 10 years

but it has never seemed like it needed it. I do a seafoam decarb once a year for the last 5 years or so. Just replaced plugs, changed h2o separator and foot grease as part of annual maintenance.

Need to get this solved - so lets hear some expert opinions pleeeeaaaaase! I could post a video if it helps but it will be this weekend.

Blue_Runner · #2 05-29-2018, 04:36 PM

what about fuel pump? Was thinking maybe not that if it is fine at WOT?

spareparts · #3 05-29-2018, 06:48 PM

go back thru the carbs, replace the fuel pump diaphragms. If you haven't done it since the last time, replace the fuel lines with new line as well(tank to engine). Make sure you get an OEM primer bulb(Yamaha, Merc, or Bomb)

Blue_Runner · #4 05-30-2018, 07:31 AM

Thanks for the advice Spare, already replaced fuel lines so I'll get to work on the the carbs, primer bulb, fuel pump and inline filter and see if anything changes.

THEFERMANATOR · #5 06-02-2018, 04:38 PM

I was gonna say it sure sounds like a plugged air bleed or something.