Yamaha F115 Starting Problems

[BWillis88]

Yes the IAC is clicking on shutdown, thank you for that info.

i disconnected at the primer bulb and used the primer bulb on my 12 gal tank. I guess it is possible there is a restriction not allowing enough fuel? I know some was making it to the fuel rail and injectors, had 45 psi and saw fuel coming out injectors when i was still troubleshooting. Will definitely check before i hook back up to main tank.

[99yam40]

It is. SHE RUNS AGAIN!!!! I promised an update and as bad or ashamed as I am here it is. Not saying everything I changed didn't need it for a healthy tune up, being new to me and all but the last issue appears to be nothing more than "bad" 2 week old gas. I did put regular pump gas in it with a stabilizer so it really hasn't crossed my mind. Took my 12 gal tank off my old 40 HP 2 stroke Evinrude, that I only run Ethanol free in, and after clearing the line she fired right up and it running great! I guess going forward it's ethanol free for me.

Thanks for everyone's help, definitely wont be a stranger, this is a great community.

If bad gas is correct, remember you need to get all of it out of the tank.
meaning sucking out only what you can thru the normal pick up tube is not getting it all out

also the clicking when key was turned on has me thinking bad gas was not the problem, but lets hope you got it solved

[BWillis88]

Good morning again everyone, I'm bumping my old thread to say thanks and say that bad gas may not have been the whole problem but it did help me identify another issue. The load of water in my fuel was due to a hole in the tank, problem found and repaired. Tank drained and cleaned, more ethanol free pumped in .

Current issue is bogging down when under a load, put the boat in the water Saturday, fired right up, idles out of the marina, push throttle up to 2200 or so and does ok, start to go higher and it coughs, chokes, bogs down, push throttle all the way and nothing, bring it back and it runs fine at 2200-2400 RPM. Go back to dock check fuel/water separator and its all clean, check fuel filter cup at back of motor, all clean no water in system. Go back out, same problem, check everything again, open up the drain plug on VST and pump a bunch of fuel thru just for good measure. Go back out, the RPM does go a little higher, 3400ish but you can tell the motor doesn't really like it, head out of the cove hit a few waves 5200 and we are hauling! Hit a few more waves and motor will barely make 2000 and we limp back to marina. Get home, check everything again, no water in system, fuel pressure gauge on rail says 40 psi, oh and the whole time the motor will fast idle all the way up no problem, fuel psi stays steady.

Afterwards I pulled my high pressure pump, checked VST filter, its clean and found no water in the pump/VST bowl.

Oh and TownsendsFJR1300, the IAC worked perfectly the whole time, clicking only on shutdown.

Any ideas?

[99yam40]

what was the fuel pressure when the problem showed up?

[BWillis88]

That i am not sure of, didn't have my fuel pressure gauge at the lake but that is what I am going to try next, in the driveway, not under a load, it stays right at 40psi, idling and reving it up.

[TownsendsFJR1300]

With the hitting the waves and then a change, makes me wonder if all the water is out of the tank.

Was the tank pulled, or just emptied by priming the primer bulb into another container? IE, if so, you may still be mixing up just a tad of water(from the bottom of the tank).

As you noted, simply draining the VST, CATCHING it in a small container to examine it is critical....

I'm assuming just water was in the tank or could any other type of debris get in there (with the prior leak)?

[99yam40]

That i am not sure of, didn't have my fuel pressure gauge at the lake but that is what I am going to try next, in the driveway, not under a load, it stays right at 40psi, idling and reving it up.

I have found that testing pressure while everything is good gives good readings every time

[zenoahphobic]

I have found that testing pressure while everything is good gives good readings every time

This thread appears to me as a possible example, where things are changed/ cleaned/replaced enthusiastically without knowing what the problem is, repeatedly, without progress.
Although it is sprucked as "good maintenance" to do these things, it however is a poor way to do "good diagnostics".

[rodbolt17]

me??/
I would disconnect two plugs and rev the snot out of it on the muffs.
revving a motor with no load is a teat on a boar hog.

[BWillis88]

me??/
I would disconnect two plugs and rev the snot out of it on the muffs.
revving a motor with no load is a teat on a boar hog.

What should I look for while doing this? With 2 plugs off if it runs I imagine it wont make power or RPM. You thinking coil packs going bad under load? Only test i saw in manual was the resistance check, which they passed but i could do a dielectric test and see if the insulation is breaking down, perhaps grounding out under a load?


TownsendsFJR1300, yes tank was drained and pulled from boat. The last 2 times i pulled water separator filter and fuel filter, post tank pulling, no debris was seen but possible earlier debris in fuel rail/ injectors i guess is a possibility.

[99yam40]

I am fairly sure Rod was getting at the motor will rev up with no load on motor even with some cylinders not firing, so it is useless to even do that (rev with no load)

[BWillis88]

latest update; 3 hours on tha lake today, got home and checked fuel water seperator all clear, looks like tank flushing and repair is all good.

yesterday used a spark gap tool and set it to 1/2 inch based on other threads to "simulate" load on motor, nice blue spark on every cycliinder. Did the at home fuel injector cleaning, cyclinders 1-3 after a few seconds had a nice stream with a "halo" spray around it, cylinder 4 injector even after minutes of cleaning would never do more than a fog or mist. Still have old injectors, tried 2 and both had nice streams like first 3 i cleaned, so used one of those.

Today on the lake immediately got 1,000 extra RPM, but still would not get above 3,400. Put my fuel presuure guage on the rail, idling it would make 40psi, as soon as you pushed the throttle up psi would drop to 30. i sprayed a little starter fluid into the intake and RPM would rise, also noticed bulb seemed a little soft, could squeeze it and psi would rise a little, momentarily.

Low pressure mechanical pump not keeping VST fuel? Thoughts?

[rodbolt17]

at 30m psi it is to lean to run correctly. keep trying and you will post about piston or ex valve damage. myself I would find out whether a VST or other filter is clogged, can you keep the vst full and is the VST pump grommet ok.