Looking for opinions. I am about to take my boat to the shop to clean out the carbs. When I told the mechanic that it was a carbirated 40hp 4 stroke, he told me that it was one of the worst motors yamaha has made. He said they get clogged up very easy and yamaha quit making them. Anybody else heard this? I thinking my may be better off selling the boat rather than fighting with it if it stops up regualarly. Thanks
Had a 40hp come into the shop last week. Was coughing and weezing at idle and was over heating. soaked carbs in cleaner for couple of hours and reinstalled but still run bad. tore down again and resoaked 4 hrs ... still same problem. carbs looked very clean finally soaked for 12 hrs and reinstalled new gaskets and needle and seat. when reassembling i used magnafying glass and looked at the 8 very tiny idle circuit holes and a couple were still slightly clogged. long story short, pay very close attention to the tiny holes and make sure you have good flow through each and every hole. good luck!
Yamaha recommends using an ultrasonic cleaner instead of the traditional carb cleaner on those particular carbs. The agitation from the ultrasonic seems to do a better job of getting up in those tiny passages. We use it on all the carbs.
One of Yam's most complex carb's.
yami does not make the carbs
hondas are even worse
you need to use an ultrasonic cleaner with their fluid!
Reply With Quote
HUMAN BUILT = HUMAN FIXED 
<U>CERTIFIED MARINE TECHNICIAN</U>