gas in oil

[searocketdesigns]

2006 115hp 4 stroke yamaha, 100hrs... i have gas in the oil, can that be caused by a leak in the rubber diafram in the fuel pump on the cam cover? also, if there is too much oil in the system, caused by the fuel in the oil(about half a quart) will the engine sense too high oil pressure and put the engine in safety/limp home mode by lowering the fuel pressure? please advise.

[99yam40]

Thinned out oil with gas will just cause lower oil pressure and more wear inside the motor due to less lubrication.

Usually stuck open stats causing motor to run too cold, over propped causing lugging of motor, or idling /running low RPMS too much will cause making oil.

I do not know if pump will

[boscoe99]

The F115 uses a switch that senses low oil pressure only.

If and when the switch closes due to low oil pressure the motor goes into RPM reduction mode. Ignition and fuel injection are terminated to certain cylinders in order to reduce the engine RPM.

There is no sensor or switch used to detect an excessive oil pressure condition.

On a 2006 model year motor first thing I would check is the fuel pump diaphragm. Certainly a rupture of the pump diaphragm can allow gasoline to get into the oil supply.

[searocketdesigns]

yamaha 115 4 stroke

the problem i am having with the engine is: engine starts and idles fine, as i increase the throttle to 2600 rpms all is fine, as soon as i go to 2700 rpms, the engine speed drops back alot, it won't go faster. we put a fuel pressure guage on the fuel rail as it was running, the pressure was 40psi, but at 2700 rpms, it drops to 20 psi. i have read that the ethonal fuel i was running may have clogged the injectors or the vst fuel pump. i have drained the fuel tank, everything looks fine inside the stainless steel tank, changed the water/fuel filter and the filter on the back of the engine, i ran a can of seafoam cleaner though the system, i just checked the fuel pump for leaks, it looks ok... now i need to refuel with ethonal free fuel and test.

[boscoe99]

the problem i am having with the engine is: engine starts and idles fine, as i increase the throttle to 2600 rpms all is fine, as soon as i go to 2700 rpms, the engine speed drops back alot, it won't go faster. we put a fuel pressure guage on the fuel rail as it was running, the pressure was 40psi, but at 2700 rpms, it drops to 20 psi. i have read that the ethonal fuel i was running may have clogged the injectors or the vst fuel pump. i have drained the fuel tank, everything looks fine inside the stainless steel tank, changed the water/fuel filter and the filter on the back of the engine, i ran a can of seafoam cleaner though the system, i just checked the fuel pump for leaks, it looks ok... now i need to refuel with ethonal free fuel and test.

There's your problem.

The VST filter may look fine while is can be so clogged as to restrict fuel flow.

It is not ethanol that clogs injectors and or the VST filter, it is debris.

What about the fuel filter from the mechanical pump to the VST? When was the last time that it was replaced.

[searocketdesigns]

i replaced the filter between the first fuel pump and the vst, last year, and i just replaced it yesterday, but i haven't run the engine yet. i haven't done any work to the vst and it's filter yet.

[rodbolt17]

takes about 20 min to remove,dissasemble,inspect and reassemble the mechanical pump.

as its a blow through style pump,brush dust from the pump motor can and will clog the VST filter.