2004 Mercury 115 2 stroke - oil injection block off plate

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griggsmars

Petty Officer 3rd Class
Joined
Jun 10, 2010
Messages
92
Hello, I would like to remove my oil injection from 04 Mercury 115 EXLPTO 2 stroke outboard. The motor is on a pontoon boat that I always fill with gas cans. I have been having an issue with oil leaking from the holding tank and think it would be easiest to simply block off the oil injection and mix the fuel. Does anyone have any advice on this option and if they know what block off plate to purchase and how difficult the job is. Thank you, Mike,
 
B

Boats Pal Marine

Cadet
Joined
Aug 17, 2025
Messages
6
If you’re looking to block off the oil injection on a 2004 Mercury 115 2-stroke, you’ll need a simple oil injection block-off kit/plate. Mercury used oil injection on those motors, but a lot of owners choose to remove it and premix their fuel for peace of mind.
  • The block-off plate itself is just an aluminum plate (usually sold as a kit) that covers the spot where the oil pump mounts.
  • You’ll also want to remove the oil pump and gears, then install the plate with the proper gasket or sealant.
  • Kits are available from aftermarket suppliers like Boyesen, Pro Marine, and on sites like eBay, Amazon, and many marine parts stores. Search for “Mercury 2-stroke oil injection block off kit” – they’re usually under $30–$50.
  • Don’t forget to plug or cap the old oil line fittings and run the motor on 50:1 premix after the conversion.
It’s a straightforward job if you’re comfortable with basic wrench work, but follow the service manual for torque specs and proper sealing.
 
Texasmark

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,818
I have done that to two engines, 90 and 115 Mercs. All I did was to unscrew the oil pump and remove 1 of its hoses (so that I could pull it back), pull it back, remove the gear/drive shaft...easily removed just grab it and pull) and put things back. left oil in the tank as it wasn't bothering anything. Since you have a leak, then drain the tank mox-nix.

Oh spending a good portion of my life with pre-mix I was accustomed to doing that. When internal oiling systems came out I got used to not premixing. After the above mentioned modification, I wrote the premix ratio adjacent to the fuel filler so that I wouldn't forget.........
 
G

griggsmars

Petty Officer 3rd Class
Joined
Jun 10, 2010
Messages
92
Thanks for the replies. I ordered the block off kit and hope to do the install next week. Thanks again for the info. Mike
 
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