yamaha 225 power issue

[aaloift]

hi
\have a yamaha 225 2 stroke carburated, revs great in nuetral when in gear has no power and its on an 18 ft javalan boat any suggestions?????

 

[racerone]

In nuetral even a motor running on 4 of 6 cylinders will rev up, means nothing.-----------Do a compression test, followed by a test that that you have spark at each cylinder that will jump a gap of 7/16"------------Is this something that developed suddenly ???