Oil Injection Removal on Mercury 2.5 Liter Laser Motors

Acknowledgements

This would not have been possible for me to do without the knowledge gained from the many members of Scream and Fly. Particular thanks goes to Pyro for outlining the steps and to Hunter for providing a couple of the photos used for this document.

Tools and supplies needed

You will need some basic hand tools consisting of sockets, pliers, screw drivers, wire cutters, etc.
Muffs, or some means to start and run the outboard on a garden hose.
Zip ties
Rags

You will also need a block off kit for the motor. This consists of the following

NOTE: The first two parts should be available from any Mercury dealer.
Here is a picture of the complete kit.

First step is to premix the fuel in your tank to the specification that you will be using. Most recreational/fishing outboards will run a 50:1 mixture, the race motors (Pro Max) will use a 40:1 mixture and higher performance motors turning in excess of 6700 rpms will use an even higher mixture. Start and run the motor for a good 5-10 minutes on the garden hose. IMPORTANT! Do not skip this step! The reason for doing this is to get a good fuel/oil mixture into the fuel system. Failure to do this will result in straight gasoline with no oil going into the motor on first startup after removing the oil injection.

After running the outboard disconnect the battery.
Remove both oil tanks and all associated hoses. Pinching the hose to the oil pump with vise grips will lessen the oil mess. On some motors, you have to temporarily remove the ECU and upper bracket to remove the oil tank. No big deal.

Disconnect the oil cap wires from the warning module (one light blue/white wire and one black ground wire).

Disconnect and remove the rotational sensor. It is located on the port side of the engine above the oil pump and has a light blue/white wire, a white wire and a black ground wire coming off of it. Refer to the following picture and note in the upper right the black circle.

Remove the throttle interconnect linkage to the pump and remove the oil pump assembly (pink circle above). Since the small bolts that hold the oil pump on may be hard to access on your motor, you will probably need to take out the bolts that hold the vapor separator on (red circle above), and remove some fuel lines and a couple of small bleed lines to move it. You'll be able to swing the assembly slightly out of the way to access the oil pump's bolts. Slide it out, and replace it with the plastic block off Theo-ring should be installed on its shaft detent. Flat side of the shaft faces the crank. This plug will prevent the bushing from falling out inside your crankcase.

Theincoming oil fitting on the vapor separator is a check valve. If you simply remove the hose from the barb, it will probably be fine. You can replace the fitting with a plug if you want, or as mine is, simply install a screw with a plastic zip tie to block it off. Refer to the following picture.

Theoutgoing air pressure fitting on the starboard side of the block below the starter is also a check valve, but it needs to be removed and replaced with the threaded pipe plug.

All wires that were disconnected should be capped off and tied neatly with the other wire bundles. Once that is done, reconnect the battery and enjoy the peace of mind knowing that your outboard will happily receive the oil that it needs.