2007 115 hp Yamaha 2 stroke engine misfire.

[rkmnoles]

This engine has been flawless for years and recently started misfiring. A plug change will cure the problem for several trips and then it will happen again. It is usually the top plug on port side. Could this be a coil issue. Thanks in advance.

 

[jerryjerry05]

Could be??

Do a compression test.
Use a GOOD tester.
Harbor freight tools don't give good results.
U-tube has a few good video's on how to do the comp. tests.

Some say hot engine, some say it really doesn't matter.
You should get results both ways.
Just make sure they're all within 5# of each other.

 

[QBhoy]

Hi
that will be a rare beast. A 2007 115 2 stroke.
that aside, yeah. As said, do a compression test on her.
also hate to fear the worst, but I bought a fixer upper boat recently with a 115 V4 yam. The engie was said to be done for, but they didn’t know why. Turns out they had let the bilge of the boat almost totally fill with water. This meant that the remote oil tank took water too. The old thing ran for as long as it could then eventually lost a cylinder. It still ran though, but quite a lot like yours does or a bit worse. Check the oil tank isn’t diluted.