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(NEED HELP) Removing 1997 Mercury 90hp 2stroke VRO pump and bypassing.

H

Harryyabs

New member
I’m new to this so apologies in advance.

Went to fill up my oil reservoir today to find that fuel had leaked back into oil tank, stinks of fuel. I’ve been told to just bypass VRO system as oil is also leaking.

I’m not an idiot but I’m also not mechanically experienced, I’ve been told that I just need to drain and remove oil reservoir tank and remove oil pump drive shaft and put the pump back on.

is this really all I need to do? Do I not need to cap/remove/loop any pipes from the pump to fuel pump? Do I not need put something where the oil pump drive shaft was originally?

I am at the hands of your knowledge, please help me.

all the best,

h
 
I would fix the problem and leave the oil injection system alone. I'm trying to understand how gasoline is getting into your oil tank. Its usually the opposite that oil leaks back into your fuel system because of a bad 2 psi checkvalve in the oiling line running to the fuel pump.
 
fitz73222 said:
I would fix the problem and leave the oil injection system alone. I'm trying to understand how gasoline is getting into your oil tank. Its usually the opposite that oil leaks back into your fuel system because of a bad 2 psi checkvalve in the oiling line running to the fuel pump.
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I have been instructed that the fuel pump may need looking at as it could be the one way valve is broken allowing fuel back through.

do you not think I should just scrap the VRO system all together and just premix? How hard is it to do? Cheers mate.
 
Mercury oil injection systems are extremely reliable and failures are very rare. VRO was an OMC term for their oiling system and typically had more issues than the Mercury system. Generally speaking, oil injection was one of the best advancements in two stroke engine reliability. Many people do not mix oil and gas reliably at the correct ratio's and can lead to severe carbon build up or the a oil lean condition and melt bearing surfaces. Additionally, an engine that has had it's oil injection system disabled is worth less money and less salable.
 
fitz73222 said:
Mercury oil injection systems are extremely reliable and failures are very rare. VRO was an OMC term for their oiling system and typically had more issues than the Mercury system. Generally speaking, oil injection was one of the best advancements in two stroke engine reliability. Many people do not mix oil and gas reliably at the correct ratio's and can lead to severe carbon build up or the a oil lean condition and melt bearing surfaces. Additionally, an engine that has had it's oil injection system disabled is worth less money and less salable.
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I appreciate that but I’m really not worried about reselling the engine it’s more for my use for the next year or so. The oil leak is an issue and I feel removing the pump will void that.

as for the issue of fuel getting into the oil, how hard are the fuel pumps to change? Where shouts is the one way valve located to check if it’s working properly?
 
The best advice is to purchase a factory service manual and familiarize yourself with the system so you can locate and diagnose the parts of the system. The factory Service manuals are easily obtained on ebay. Good Luck...
 
Cheers, I might take the fuel pump apart and see if it’s the diaphragm, would my engine have an in-line oil filter that could have failed sending fuel back into the oil?
 
A manual is just going to show me how to fix the problem. I don’t even know what the problem is yet.

I will look for a manual but I’m hoping someone on this forum will actually know.

cheers!
 
Harryyabs said:
I appreciate that but I’m really not worried about reselling the engine it’s more for my use for the next year or so. The oil leak is an issue and I feel removing the pump will void that.

as for the issue of fuel getting into the oil, how hard are the fuel pumps to change? Where shouts is the one way valve located to check if it’s working properly?
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When my 2002 got to be 10 years old, I decided to add oil myself; same basic engine, size, type, just later upgrades. I removed a couple of the 3 hoses from the pump for convenience in getting it out to be reinstalled on going back together. Removed the 3 or 4 screws attaching it to the engine and pulled it out exposing the drive gear and shaft...and any little parts that may be there.....were none. Pulled the shaft/gear out.

Reinstalled the pump the reverse of the removal. Didn't pinch off any hoses, didn't drain the onboard oil tank, did nothing else. Wrote on the boat at the fuel fill connector to add 1 pt-6 gallons of gas. That's it. Engine is still in service with a local fire-rescue dept..

My engine, my money, my decision. To each his/her own for whatever your reasons. My reason was that I slept better at night.
 
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I completely agree. However after looking at the issue of fuel in oil tank further I think it could be the fuel pump has failed allowing fuel to go back through to the oil tank.

when you disconnected the oil system did you leave the drive shaft out of the pump or replace it with a plastic one that is void? I’ve been told that if you take it out it can lead to issues with the crank volume. Also did you just put the pump housing back on or just put a cap plate on it?

cheers in advance.
 
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