Fuel flow problem

S

snal

New member
Sorry...this is on my pontoon boat.
Engine starts fine, slight erratic idle, idles out fine in gear at 1000-1200rpm with erratic symptoms gone. Throttle up quickly or slowly and it will not throttle past 15-1800rpm. If I put it in neutral...it revs fine! Same in forward or reverse.
At first, the bulb was sucked semi-flat (new bulb...old line)...switched tank flow to reserve (has 3/4 full tank) and the bulb would get full, but not hard. Installed complete new fuel lines, quick connect, and bulb, Nothing changed!
Screen at engine is clean, no other filters. Bulb seems to build pressure, then move fuel...rather than firm up. No line leaks, no leaks at engine, no leaks anywhere.
Thoughts?
 
Open the vent on the tank, point the arrow on the bulb up when squeezing. This will help the one way valves seat. If that doesn't work plug in a totally other fuel supply.( Your buddy's boat tank.) This would tell you if its a fuel supply issue or a motor issue. Also check the engine fuel line connection I know Yamaha's are very fussy and like the factory ones the after markets seldom work for me.

Good Luck

Chris
 
After doing as Chris has instructed ...if you determine it is a fuel delivery problem, then check one additional place...fuel pickup tube (Screen Filter on the end).

Good Luck
 
yeah,it sounds like it is not venting fast enough (fuel is leaving the tank faster than air can get in), creating a pull against the flow of fuel
 
Thanks guys...checked the vent this morning, no restriction found. I'm heading down now to spray some carb cleaner while at idle...checking for air leaks.
Lots of volunteered portable fuel tanks here at the campground, so I'll try that as well.
 
Spraying carb cleaner didn't indicate any air leaks, spoke to a local mechanic that instructed me on how to check the engine temp sensor that could prevent the engine from revving higher than 2k rpm...checked out fine.
It's a beautiful day...so all volunteered fuel tanks are currently being used.
 
Fun Patrol":2i6o6m80 said:
If it's sucking the bulb flat you have a clogged screen on the tank pickup.

..Roy
Click to expand...

Could be...but I have 2 independent pick-ups in the tank...one main..one reserve...and I switched between them. Still, both could be clogged. The 2 independent pick-up lines share the same switching valve, and I did check the valve. Can't check the separate lines by hooking to them individually because the hoses are larger diameter than the line to the engine.
I've tried 3 different bulbs, so apparently it's not the check valves in the bulbs.
The bulb got sucked flat once during my testing, hasn't occurred again, but the bulb(s) still pump full of fuel...but don't get "firm" like they should. This may indicate at least one stuck float (1995 88hp SPL V4)
 
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