F115TXRD 2005 surging

[MattF115]

Surging under load anything above 4000rpm fells like it shuts down what ever RPM your traveling at to 0RPM then back to what your set at. I have gone through the fuel system have 42psi on rail cleaned injectors replaced filters and yes in the VST. I think its electrical but not sure i seem to lose more RPM as boat gets warmer i did replace water pump as well. any help would be great

[fairdeal]

if you've monitored the rail pressure while running the boat -
and its still a steady ~42 psi right up to 4000 rpm,
then seems like its not a fuel problem

but then "shuts down what ever RPM your traveling at to 0RPM then back to what your set at. "
doesn't sound like a fuel issue, either

in fact it doesn't sound like anything I've ever heard of -
"0 rpm" - to me - means the motor is stopped -

[MattF115]

its like it is shutting itself off but does not stall out the engine this all happens in mill seconds i seen another post on here with same problem but it was an 2003 F115 but never found out what fixed his problem

[MattF115]

Dehayrf1
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#1 2003 Yamaha F115 cutting in and out at higher RPM's

07-17-2020, 02:46 PM
I have a 2003 Yamaha 115 4-stroke on a 24' pontoon boat. This past weekend we took the kids tubing. Motor ran great, we pulled them around for a few hours with no issues at all. Then, as we were making it back to the launch, we accelerated, and at around 4,000 RPM's, the engine cut way back, to about 1500 RPM's. I immediately pulled the throttle back and let it sit for a minute. Tried to accelerate again, and the same thing happened...accelerated smoothly, but when it got up to the higher RPM range, it dumped back to the mid 1000's. This time, I didn't pull the stick back, and it shot straight back up to the high RPM's after a half second or so, and then back down, then back up, back down, like a bucking bronco. After a couple cycles of that, we decided to limp back to the launch. It runs smoothly, no sputtering, it's like it's on or off, on or off, not like it is running on fumes. It should also be noted it didn't appear it was doing it at one specific RPM, and dumping back only to one specific RPM...it was just dumping from a higher RPM (in the plus or minus 4,000 range) to the mid 1,000's range.

Anyway, because we had been out all day, I was hopeful I was just running low on fuel, or maybe had a cracked fuel pick-up, or something along those lines. So I pulled the pickup tube, and it was solid. It was somewhat low on fuel, so I filled the tank and took it back to the river to try it again in hopes it was just sucking air when we were accelerating. Long story short, it is still doing the same thing. Posted a link to a video of it. https://youtu.be/HmkkZSSFo0o

LIke I said, it isn't sputtering or acting like it's running out of gas, it's like it is on or off, on or off.

Any ideas?

I have same problem

[99yam40]

does the rail pressure stay at 42 when the motor is stalling?
if it drops off then that means the injectors are not getting the proper pressure to deliver the proper amount of fuel

[MattF115]

I have a 2003 Yamaha 115 4-stroke on a 24' pontoon boat. This past weekend we took the kids tubing. Motor ran great, we pulled them around for a few hours with no issues at all. Then, as we were making it back to the launch, we accelerated, and at around 4,000 RPM's, the engine cut way back, to about 1500 RPM's. I immediately pulled the throttle back and let it sit for a minute. Tried to accelerate again, and the same thing happened...accelerated smoothly, but when it got up to the higher RPM range, it dumped back to the mid 1000's. This time, I didn't pull the stick back, and it shot straight back up to the high RPM's after a half second or so, and then back down, then back up, back down, like a bucking bronco. After a couple cycles of that, we decided to limp back to the launch. It runs smoothly, no sputtering, it's like it's on or off, on or off, not like it is running on fumes. It should also be noted it didn't appear it was doing it at one specific RPM, and dumping back only to one specific RPM...it was just dumping from a higher RPM (in the plus or minus 4,000 range) to the mid 1,000's range.

Anyway, because we had been out all day, I was hopeful I was just running low on fuel, or maybe had a cracked fuel pick-up, or something along those lines. So I pulled the pickup tube, and it was solid. It was somewhat low on fuel, so I filled the tank and took it back to the river to try it again in hopes it was just sucking air when we were accelerating. Long story short, it is still doing the same thing. Posted a link to a video of it. https://youtu.be/HmkkZSSFo0o

LIke I said, it isn't sputtering or acting like it's running out of gas, it's like it is on or off, on or off.

Any ideas?

I have same problem

[MattF115]

I found that post but never found out what was done to resolve problem

[99yam40]

you did not answer my question about the rail pressure

[MattF115]

I never left fuel pressure gauge on when on the lake just with pucks on at home i thought it was fuel so i took fuel system right apart thought i was sucking air pulled line out of fuel tank right to the VST i cleaned the injectors but have not tested under load with clean injectors.

[99yam40]

if you want to eliminate something you will have to do testing while the problem shows up

[robert graham]

Is your fuel tank/fuel system venting properly? …..what kind of fuel tank do you have?…..maybe try loosening the fuel cap a bit and run the motor….just a thought…

[Keithbaja]

Run with a portable fuel tank, remove anti siphon valve at tank. Replace fuel line and primer. A clear vinyl fuel in the system will show wonders.... DUH !!

[panasonic]

Run with a portable fuel tank, remove anti siphon valve at tank. Replace fuel line and primer. A clear vinyl fuel in the system will show wonders.... DUH !!

All good advice Kiethbaga for sure. Just leave out the "DUH" next time. People come come here for help, not to be made out to be idiots.

[MattF115]

I have ran an external tank with lots of venting no difference replaced fuel line from tank to water separator replaced fuel line after primer ball to engine as well have not replaced primer ball yet. there has been no change. When this all started i was pulling tube running engine hard and it fell on its face at 5500rpm it cut out at did not stall but lost all RPM. Hoping to get out Friday on the lake and do more testing monitor fuel pressure under load.

[MattF115]

Out on lake right now first thing this morning launch boat ran wide-open at 5800 RPM for 10 minutes turned around on the lake was heading back to the dock all of a sudden it kicked out put a fuel gauge on it under load maintaining 42 psi and when the engine kicks out it definitely loses fuel pressure but it’s electrical like it it’s not kicking out as an a lost fuel pressure