Yamaha idleing problem

[littlefeet]

Hi all,
Last week I installed new plugs in my Yamaha 115 salt water special year 1998. I put it in the water it ran well for about 20 min. went back to dock. Next run started out ok, after 5 mins. motor stopped. Limped back to dock. Here are the symptoms: runs well at above 14oo rpm. will not idle, choke helps some. Hooked to alternate fuel system, no help. While running engin above 1400 pulled each plug wire off one at a time, first 3 made no change in engine. when I pulled the last off motor died. (replaced each b-4 removing next) Checked compression each cyl 125 to 135 psi. Any ideas?
Thanks for any help. Bob

 

[Ray Neudecker]

Re: Yamaha idleing problem

Sounds like you need to go through the fuel system, likely including rebuilding the carbs and replacing the fuel pump.

 

[JUSTINTIME]

Re: Yamaha idleing problem

so u have spark to all cylinders?

 

[grid]

Re: Yamaha idleing problem

That it runs well over 1400 says spark is okay; you have good compression; all that's left is the carbs, and I think you swallowed some junk in them. Trying a new gas tank after the fact won't tell you anything. Check the engine's fuel filter for clues. Then R&R the carbs for sonic cleaning.

 

[JUSTINTIME]

Re: Yamaha idleing problem

it has a high and low speed stator also

 

[grid]

Re: Yamaha idleing problem

Choke helped. Stator wouldn't affect fuel flow. Then again, this is a holiday week, so anything might happen!

 

[AGENT 37]

Re: Yamaha idleing problem

Maybe the carbs just need adjusted but if you want to do a simple check on the fuel pump you can try pulling the output line off of the fuel pump and check a couple of things, first squeeze the primer bulb and see if a steady stream of fuel comes out indicating a leaky diaphram allowing the motor to get too much fuel. Second... maybe crank the engine and see if fuel pumps out of the output side as it should. If the fuel pump is bad it could be either allowing too much fuel to the motor or not enough. I'm no expert, but it got me once. I had the same symptoms when I pulled spark plug wires while it was running. I went through the whole ignition system before I found the pump. Working on turbine jet engines can occasionally get you thinking the wrong way about the other stuff. Oh yeah....and don't smoke if you work on the fuel system.

 

[Ray Neudecker]

Re: Yamaha idleing problem

Easy way to check the fuel pump is to back off the two mounted bolts far enough to allow it to move away from the block. Squezze bulb and see if fuel leaks out behind the pump. If so replace the fuel pump.