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How do I disable the oil injection on my 1991 115hp Mercury

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shemp0091

New member
I would prefer peace of mind on my older 1991 Mercury 115 hp 2 stroke and just premix my gas. I wanted to know the proper way to disable the oil injection. Will plugging up the oil feed tube be ok, or will that do damage to the fuel pump?
 
Reroute the oil feed line into the oil tank and let it run in a loop w/a small amount of oil in the tank. If you sell it the new owner can reconnect it.
 
Wow! Good thing you asked. Here's why:

That motor is unique in that the bottom two carbs do not have any idle fuel flow--the motor runs on the top carbs ONLY at idle. So, if you go with premix only, the lower cylinders will not see any lubrication at idle, and there goes the bearings, pistons, etc.

Jeff
 
Thank you so much for the input. If you dont mind, please educate me on how premix or using the oil pump makes a difference in how the lower cylinders get lubricated. In my thinking by premixing i am meerly doing the job of the oil pump. The oil pump itself has one line that runs directly to the fuel pump to mix with gas before going to the carbs. The is no separate oil line that provides oil to the bottom 2cyls only.
 
The automatic oil mixer injects oil into the fuel line before it goes into the carburetors !!!!---So 50:1 will work just fine on these motors !!!-----The bottom 2 cylinders have very small carburetor jets for idle.--This means just a little bit of fuel and oil go in for lubrication and cooling.---Cylinder does not fire with that little bit of fuel.---Amazing how much mis-information is out there !
 
Thanks to all of you for your input. After reading all of your comments and doing a bit more reserch I'm feeling confidnt that a 50:1 premix will work just fine.....Thanks again
 
YOU can run this motor on pre-mix, but I sure as hell wouldn't!

Jeff

PS: On our old dirt bikes, we used to blip the throttle constantly when descending a long hill, so the motor would see a bit more oil (as the gas came through). And they had an idle circuit.
 
YOU can run this motor on pre-mix, but I sure as hell wouldn't!
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It doesnt matter at all as carbs are filled with fuel ,only bottom 2 are dejetted per say to allow just enough fuel /oil to cylinders to prevent seizing but little power output.Engine wont care if its oil injecteded or premix...
 
..."bottom 2 are dejetted per say to allow just enough fuel /oil to cylinders to prevent seizing ..."

What "oil/ fuel" mixture, since the motor uses oil injection! (There would be NO oil coming in from its idle jet system which is NOT there). Furthermore, the ONLY way those two lower cylinders can run without seizing is for there to be NO gas coming in at all. Running a lean idle mixture would damage the those cylinders, so they run totally without ANY combustion at all at idle, the oil injection system supplying the oil needed to prevent damage.

For that reason the owners of these engines notice the lower cylinders suddenly "kicking in" when the throttle up--they go from NO combustion to mid-range power instantly.

I repeat: deleting the oil injection on these motors and going solely pre-mix will destroy the engine!

Jeff
 
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Sorry Jeff--You need to look into how the 2+2 system works !!!!--The oil is mixed with the gas before the carburetors !!!
 
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Dude... throw away your SELOC manual!!!!!!
Furthermore, the ONLY way those two lower cylinders can run without seizing is for there to be NO gas coming in at all.
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You cant run em dry as they will seize due to friction..
For that reason the owners of these engines notice the lower cylinders suddenly "kicking in" when the throttle up--they go from NO combustion to mid-range power instantly.
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If the system is set-up correctly you will never notice the bottom cylinders kick in unless you pulling skier/tubes. The reason for "kick" is the accelerator pump and mini injectors under electrical plate that shoot fuel charge in along with increase in air flow thru lower carbs which internal metering starts flowing fuel. Bogging problems with these motors are usually do to: incorrect sync/link of carbs and accelerator pump, dirty/restricted injectors,accelerator pump diaphragm weak or low fuel pressure from fuel pump to carbs/accelerator pump.
 
If the system is set-up correctly you will never notice the bottom cylinders kick in unless you pulling skier/tubes.
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Manure! Mine are set up correctly and have always kicked/surged as sufficient fuel enters the combustion chamber when passing 1750-1850 RPM.
 
Manure! Mine are set up correctly and have always kicked/surged
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No manure......On some boats /toons you may but one's I have setup/ran on bass/FS hulls you feel just a increase in power...no "kick" or surge unless pulling a skier/tube then you will notice it.
 
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