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Two stroke oil leaking into fuel hose, 30hp 1993

M

MrOtto

New member
1993 30hp two stroke Mariner serial no. 689 S 251061

Engine was tilted for two weeks. Upon start up, in ran for 3 seconds and then would not run. It would only run on starting spray fluid after that. I pushed the ball valves in the engine tank and motor connection to the fuel hose to check flow, and oily blue fuel came out. I also drained the carb and it also looked bluish.
Engine started fine after fuel line/carb was drained and fuel hose was pulling fuel from a can I use for the lawnmower.
I suspected someone had pored two stroke in the fuel tank, but when I drained the tank the fuel looked and felt ok in color and "slipperiness"
So, could two stroke oil be leaking from the oil tank into the fuel lines of the motor? Flooding the carb and fuel lines with two stroke oil.
 
Disconnecting oil injection is not an option as long as it works. It will be hopeless to teach the 10+ different users of the boat to start adding two stroke oil to the fuel tank, the risk of it running without oil is too big.

Engine starts fine after a couple of days tilted, but I can't believe it not starting and excess of oil in the fuel hose was an isolated incident.

Anyone seen the repair manual for this engine? I have only the original user documentation.
 
I was thinking about disconnecting the fuel line when the outboard won't be used for, let say a week or more, (two-three days tilted it starts fine, smokey though first 10 seconds), then I guess the check valve will be in use, with hose disconnected to the outboard, and neither oil or fuel can run back into the tank. With the hose installed there are no check valves in use and fuel and oil can run back into the hose and fuel tank.
Could E10 fuel have damaged something? E10 might have been used last year, no Ethanol blended fuel is used this year.
Anyone seen a maintenance manual so I can identify the components?
 
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Typically, there is a check valve that prevents the oil in the oil tank from gravity feeding back into the system when the engine isn't running, it appears to have one at 7:00 to the fuel filter and the nearside of the fuel pump. That may be it. I've replaced them on Mercurys before and it cured that problem.
 
I would aslo replace oil tank cap as if not venting it could allow pressure to build from heat and push oil past check valve
 
The oil is injected just after the fuel filter on the line from the fuel filter the fuel pump draw fuel from the filter. Check valve is there on the oil line to prevent fuel from mixing back into the oil line coming from the oil pump?

Can I clean the oil filler cap, probably the the vent hole is clogged from tens of years of use? Soak in gasoline or diesel fuel?

Oil is pressing on from the top of the oil tank, through the oil line into the fuel line, both into the carburetor, and back into the fuel filter and is moving back into the filter and down into the fuel tank?

Over pressure in the oil tank will help this, but also under pressure in the oil tank would stop this? The oil line check valve doesn't prevent oil moving into the fuel line, just fuel moving into the oil line?

Also the regulator in the oil pump must stay open even when throttle/gear is in Neutral, because some oil must be injected on idle, so this would also stay open even if the engine is stopped, there is just no pump moving, but oil could press through just by hydrostatic pressure?
 
30 year old motor,worth $200 in parts, no need to argue virtues of design and function. Replace check valve and make sure the cap is venting. Do that and see what happens.
 
I put the hole cap for the oil tank in nafta overnight and pulled it apart and cleaned all holes. The valve in the cap looks to be a one way valve letting air in to prevent vacuum forming and oil not getting pulled out by the pump.
Hopefully it also let pressure out some way.
The check valve is not produced any more so I have not been able to source it to replace it.
 
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