1989 100hp Outboard Oil Injection Bypass

[Derek Loudy]

Hello, newbie here. Just acquired a 1989 bowrider 160 with the 100 hp outboard. Is there a how to or sticky thread on how to bypass the oil injection system and run premix only?

Thanks in advance for your help!

 

[blaster]

Out of curiosity, why bypass the oil injection? By the late 80’s mercury had pretty reliable oil injection.

 

[Derek Loudy]

Out of curiosity, why bypass the oil injection? By the late 80’s mercury had pretty reliable oil injection.

I had heard they were prone to fail, however, this is my first Merc I’ve owned. Are there any other things I should look for or update, etc.?

 

[blaster]

Not knowing the maintenance history of the motor it would be wise to make sure the oil lines and fuel lines are in good condition. The oil pump seal may also need to be replaced. Most of the problems with the oiling system on these were the alarm module causing a constant alarm. That doesn’t mean oil isn’t flowing in most circumstances though, it is more of an annoyance.

I would be certain the fuel pump and carbs are rebuilt if they have not been recently serviced as well as the water pump impeller.

Most of these motors die from running lean without enough water flow.

Do not run an AGM battery just use a regular wet cell. These motors have a weak charging system and AGM batteries can fry the voltage regulator and stator.

 

[Derek Loudy]

Not knowing the maintenance history of the motor it would be wise to make sure the oil lines and fuel lines are in good condition. The oil pump seal may also need to be replaced. Most of the problems with the oiling system on these were the alarm module causing a constant alarm. That doesn’t mean oil isn’t flowing in most circumstances though, it is more of an annoyance.

I would be certain the fuel pump and carbs are rebuilt if they have not been recently serviced as well as the water pump impeller.

Most of these motors die from running lean without enough water flow.

Do not run an AGM battery just use a regular wet cell. These motors have a weak charging system and AGM batteries can fry the voltage regulator and stator.

Thank you - I actually have a water pump on order that I'm going to put in as soon as it gets here, also a new fuel filter and plugs. The carbs looked a little damp and it looked like the fuel pump or oil pump could benefit from a new gasket. I may go ahead and order both new pumps. The lines themselves seem o.k.

I started to spray in some light degreaser and gently hose it off so I could get a better idea of where the oil or oil/fuel might be coming from, but wasn't sure that would hurt anything or not....so long as I didn't get around the coils and electronics. Looks like it was coming from top down, though, on the motor.

 

[blaster]

Keep the motor clean and you will know if there are any leaks. Most of these so called oil injection failures are due to neglected maintenance. If you want you can add some oil to the gas when you run the first ten gallons to be certain the oil level in the reservoir is dropping. I would not run oil in the gas if it is working because you will run rich and carbon up the motor. The variable oil system will be 100-1 at idle and 50-1 at full throttle. This is the more efficient way to go and will actually help the motor run cleaner.

Do not overlook the fuel pump. Most of these motors die from running lean and lack of cooling not oil injection failure.