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we have a 13 year old yamaha 175. after running for about 10 minutes, engine bogs down to low rpms, sometimes stalls. runs perfectly up to that point, up to full wot rpm. comes back to higher revs briefly when we pump the bulb. replaced primer bulb, external water separator filter, and checked fuel lines for cracks. any ideas would be greatly appreciated.
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possibly vapor lockue to clogged tank vent.
open your gas fill and run it, or run motor on an auxillary tank.
could also be a bad fuel pump, cheap and easy enough to replace. remove them, you should be able to blow UP thru them but not back down, if ANY air passes back down, the diaphram is bad. -
Check the seal(o-ring) on the strainer bowl. Also check the pipe fittings,commonly knomn as a quick connect. There is a small o-ring that may be bad. When they go bad air is introduced into the fuel lines.Comment
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great advice. thank you very much. boat is in the water, so we will try out ideas when this wind dies down tomorrow.Comment
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are you alarm buzzers working correcty? could be going into reduction, without you knowing it. also,, my 2c, is that if you run full tilt for 10 mins....your carbs are clean...its the supply getting there, thats interrupted.
if you havent ...replace ALL lines....very cheap and if you DO have the line junction at the motor...which i think they did away with in `90....rid of it....run the hose directly to the filter...or deal with the issues it will bring.
also...you might have junk in the tank...that clogs the pickup tube....again, run on an aux tank.
[ January 28, 2007, 06:29 PM: Message edited by: jb123 ]Comment
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UPDATE: Thank you to everybody for the suggestions. Finally got to the boat to try out ideas today. Vent not clogged, though monel screen was a little corroded. Took apart every inch of fuel supply line from vent to motor. No clogs or leaks anywhere. Primer bulb collapsing after running for about 5 minutes at high rpm, then motor bogs (overheat sensor working normally, had triggered after idling for 20 minutes at the dock while pumping bilge, so probably not auto rpm reduction). Finally we emptied the fuel/water separator filter, unfortunately had no clear container to see if water in it, but it did appear that there may be 2 different liquids when it was emptied. After that, the motor ran normally for over 1 hour, including 15 minutes at WOT. This was a new spin on filter that we had installed after the first time we had this problem, less than 1 hour run time on this filter! Is it possible that so much water in the tank had overloaded this filter, and the previous one also? Never heard of that happening before. Local station is pumping 15% ethanol/gas so we know that there will be more water problems, but is it possible for the water to actually clog the filter. Nothing else is clogging the lines. Next plan is to replace fiter with a filter having a clear bowl and drain plug. Any other ideas would be most welcome. Thank you again for all your help. If you're ever in Cedar Key, look us up, Faraway Inn.Comment
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Yeah it's possible for the water/fuel seperator to restrict fuel flow once the canister is full of water. You can try and install one that has a drain screw on the bottom bowl.
Thanks for posting your findings!
Good luck!Comment
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I had the exact same problem sever months ago. Contaminated gas that I purchased three days after a flood on the viginia penninsula.Comment
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