Changing the spark plugs on a Yamaha 230 HO (2007 model)
One of the easiest maintenance tasks on my boat so far.
Total time: 1 hour (includes finding the right tools). This project will probably take 20 minutes next time.
I did not have a metric gap tool so I gapped to .028 inches. It just so happened the plugs were at the
correct measurement out of the box and matched up precisely with the old plugs out of the engines.
*scroll to end of document for options
Items you will need:
1. 8 NGK CR9EB Spark Plugs – Gapped to .7-.8mm (.028 - .031 inches)
2. 5/8’s inch Spark Plug Socket
3. 8 inch plus socket extension
4. 10 millimeter wrench
5. 10 millimeter socket (not required)
6. Phillips screwdriver
7. Spark Plug Gap tool – METRIC
8. Some type of Anti-Seize/Never-Seize for spark plug threads
9. Beer (your choice)
Your enemy:
Twin Yamaha MR1 1052cc engines. 4 spark plugs each.
Removing the Air Cover
Slide the 8 air cover clamps to the open position (2 on each side)
Remove the 2 Phillips screws
Do not remove the bolt on the left side of the air cover between the 2 clamps. It does not hold the
cover on (woops on my part).
Once the clamps and screws are removed, tug hard on the air cover (it tends to stick) to expose the air
cleaner and injection system. Remove the air cleaner, it should come out easily.
Once the air cleaner is removed, the spark plug connectors are exposed (picture has one plug removed):
The following 2 steps can be done in either order:
Disconnect the Spark Plug connectors one at a time by pushing down on the tab at the top and
pulling. *Caution: unplug/remove only 1 plug at a time.
With a 10mm socket wrench, remove the bolt holding the Spark Plug cover in place. *Note: the
rearmost assembly will need to be removed with a 10mm wrench as a socket does not fit under the
air cleaner assembly:
Carefully twist while pulling to remove the plug assembly: *Note: The assembly can stick and have
some suction. Keep twisting and pulling and it will eventually free itself
Once the plug is exposed, insert a socket and “break” the plug free:
Once it is free, remove the wrench and unscrew the plug using the extension and socket:
Gap the plugs to .7-.8mm or .028-.030in. Place Anti-Seize on the threads to keep the plugs from
locking in place (more than one has broken their plugs).
Using the socket and extension, carefully put them back in the engine. Screw the plugs in using
your fingers until it stops then turn 1/8 to (no more than) 1/4 turn to snug them down.
*note: If the plug should fall out of the socket or the socket with the plug fall during installation,
please re-gap it as it may close the gap beyond tolerances.
Replace the Plug assembly, replace and tighten the bolt and plug in the connector.
Repeat a total of 4 times per engine.
When replacing the air cleaner, there is a notch to guide it on the left side (not shown). Once in
place, it should look like the following picture:
Replace the cover, screw down the 2 bolts and remember to slide all 8 clamps to the proper
position.
*note: if the air cover is on backwards, the clamps will work but the bolts will not fit correctly.
Total time, 3 beers
Options:
Spark Plug Options (more added as they are posted)
Standard
• OEM: NGK CR9EB (available over the counter at Napa/Autozone/Kragen/etc.)
Platinum
• Autolite APP3924 (This does not appear to be a correct application, These are too large)
Dual Electrodes
• NGK CR9EK
Iridium
• NGK CR9EIX (request plug caps as they are not included)
• Denso IU27
• Autolite XS4302DP
Extra Set of Plugs on the Boat
I personally keep an extra set of plugs on the boat. An excellent suggestion is to “pre-gap” the plugs
in case they are needed. While the NGK plugs have a cardboard tube to protect the electrode (and
the gap), there are some nice waterproof options such as the Kwik-Tek Plug Holder