Help w/ Troubleshooting a 25 hp Yamaha

[SunneyeDay]

I am working on a 25 hp Yamaha that has been sitting idle under a tarp for the past two seasons, but never had any previous problems. Did some standard maintenance (plugs, checked lines, etc., but put the earmuffs on and encountered some struggles. If I pump the primer she'll usually start right there and then die out shortly thereafter. Sometimes it will hold and I can really throttle it up and it will hold for a while before choking out or chokes out when I try to idle it at low.

Line has been replaced, and I have tried a couple of different tanks. I'm leaning towards a dying fuel pump, but the fact that it worked perfect before being stored for two years and will occassionally hold a constant throttle has caused me some doubt. Needle valves?

If anyone has any ideas on how to troubleshoot the problem or maintenance I should try before ordering a new fuel pump I would appreciate and help.

Thanks.

[marine_man]

If it's been sitting for two years I'd go through the carbs first. Make sure they're clean.. then you know what you have before you start buying parts.

marine_man

[broken_line]

did it sit those 2 years with a slight ammount of gas in it?? if it did my bet would be on dirty carbs and ethonal chewed fuel pump...

[Rivernut]

Had similar problem w/ 25 Yamaha that I recently bought used. An 88. I thought it wqas sucking air, and when I took off gas can cap, the tube fell off into tank. Put a hose clamp on, and it has run perfect since. Was told it is a common occurance w/ Yamaha's. Hope this helps. Good luck.