For all of you optimax users, what plugs do you guys run? Do you all run the plugs that mercury recommends which are about $15 a piece or do you use cheaper alternatives. I have a 2005 opti 150 and plan to replace the plugs this spring. I also here that you need a special wrench to get at plugs 5 and 6 so you have to have a dealer do it. Any truth to that?
Yep, they’re spendy…but shop around at your local auto parts stores. I found them anywhere from $12-$18 for the exact same plug. Checked online as well and had the same results.
#5 and #6 are a pain in the 
!! I ended up getting a flexible socket adapter (not sure if that is the correct term) and was able to get them out. When all was said and done, I wished I would have spent the $85 to have them changed by a marine tech – would have saved myself 2 1/2 hrs of frustration 
and a hand full of bloodied knuckles….
The only plugs to use in a optimax are NGK the cheapest place to buy them is at O Rileys Auto Parts. For the bottom plugs there is only one that is a pain and thats the port side plug. Use a piece of rubber gas line to start the plug.
Are you having a problem with your Opti? Mercury only recommends changing plugs when an issue accurs. They recomend indexing the plugs allso.
I was fortunate with my Opti I had another issue and had to take it in for diagnostics ( dirty injector ). They changed out the plugs ran great for 2 outings and started to act up again. Turns out I had two brand new plugs that were bad. So dealer got to change them again at there expense.
Make sure to check plug numbers with your dealer as they have made some changes as to what Mercury recommends.
And yep use fuel line to get the port side bottom plug started. Make absolutely sure that it dosen`t get cross treaded. 
A word of caution, take the boat to a dealer who has the right plugs & more importantly “Tools” because in the event you strip one of the cylinders, NOW you’ve got a really expensive proposition….” It only costs a little more to go 1st class”. 
Definetely go with the recommended plugs…
Yamaha good…. 
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