Yamaha 70 rough idle and fuel consumption

I have a 1995 yamaha 70 with about 500 hrs. Has been flawless for the first five years. Now however it Idles very rough and excess fuel is left on the water. It runs rough until about 4800 rpm. From there to full throttle 5500rpm, it seems to smooth out and run fine. 5500 is the rpm it has always reached. Fuel consumption<br />is more than double what it has been in the past. I have changed $500 dollar computer, spark plugs, and cleaned and examined the carbs<br />and choke several times. All with no change in performance. I suspect floatlevel to high<br />and passing fuel through the carboratuers but upon examination see no problem.<br />A call to the service dept. lead to purchace of new fuel pump. I have not installed it yet<br />but find this unlikely as the engine does turn up to pre problem rpm. <br />Any suggesttions? Stumpedyamaha 70

• javascript: x()<br />Frown ssavland@gci.net

Re: Yamaha 70 rough idle and fuel consumption

Savland, what are the compression numbers on your Yammy?

Re: Yamaha 70 rough idle and fuel consumption

I have not done a compression check yet. I realize that one should be done. However I still find it strange that the engine will preform at wot.

Re: Yamaha 70 rough idle and fuel consumption

That is odd. Wonder if you're dropping spark on one cylinder at lower RPM's? At any rate, I always like to start with compression to see what's happening. I'd keep the receipt for the fuel pump, I don't think it sounds like the culprit either.

Re: Yamaha 70 rough idle and fuel consumption

Savland,<br /><br />Guessing maybe the motor doesn't start real well now either?<br /><br />Had a merc once that did what you are describing and the timing was out to lunch. Most of the rpm band was a mess, but wide open it would go. If you need the particulars, my manual covers your motor.<br /><br />I can email or fax pages if you need them.<br /><br />Don't know where you are getting parts, hopefully not from the guy right next to the Douglas bridge.<br /><br />Best prices I have found are here: http://www.newagemarineparts.com/ <br /><br />Good service on parts delivery.<br /><br />PS: Moving to Juneau in May. Can't wait!

Re: Yamaha 70 rough idle and fuel consumption

Like to let people know it was a faulty fuel pump after all. I think there was a hole in<br />plastic piece between engine and pump allowing <br />fuel to flow into crankcase directly. Could not see the hole just a small crease in plastic. $45 fix. Engine now runs like knew.<br />thanks for the feedback.