weak rpm's

[weakboat]

I have a 2006 40hp 3 clynder yamaha outborad motor and it was working fine up until yesterday when it started to rough idle going down to 700 and then up to around 1200 ,I decided to take out the carbs and clean them out , the bottom carb had some black particles on the bowl when I opned it up and I did notice that the float was sticking ( could this be the problem that I need a carb kit ) well any way point is I cleaned them out and put them back on turned on the engine in a tank of water it worked fine rpm"s 1100 when idling bit rough but ok . I decided to take it out to the lake and try it out it worked fine for about 25 minutes runing full throttle at 5000 rpm's then all of a sudden the rpm's at full throttle dropped to 3000 and would not go up past that I cut of the engine and restarted it but the rpm's would not go past 3000. Can somebody out there please help me out . Thanks in advance.

 

[99yam40]

Re: weak rpm's

Check compression and spark on all cylinders. make sure timing is advancing as it should. Test the over temp and oil level alarm to make sure they work.
If all is good then clean the carbs again sound like you got more trash in jets. That trash is coming from somewhere so clean the lines and pump also.

Make sure you do the link and sync procedure like the manual says after reinstalling carbs.

 

[weakboat]

Re: weak rpm's

Thanks I will try all of that although i did do the sync and the spark plug and compression and I did turn it on this morning and it fired right up I did notice that the vent in the tank was closed so I opened it up and will go try it at the lake later this week and hopefully it will work right.