Yamaha 1999 225HP 2 stroke OX66 Top two plugs not firing

I

ibuyre111

Seaman Apprentice
Joined
Sep 16, 2003
Messages
36
Last winter I changed the head gaskets on the enging.
This spring I cranked the enging up and It ran fine for about 3 trips.
I started losing RPM's till the enging finally died.
I checked the plugs and the top two on each side were in pretty bad shape with what looked like salt water entered the cylindres.
I retightened the bolts on both heads and they were a little loose. I know I should have tightened them after the enging warmed up in the spring.
I changed the plugs and tried it again with the enging not sounding that bad but with only 4 cylinders firing. Got the RPM"s up to 3000K. I cheched and the top two cylinders were not firing. I also did not notice any water in the cylinders and the plugs looked unfired and not wet.
Any ideas would be appreciated
 
9

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,127
Re: Yamaha 1999 225HP 2 stroke OX66 Top two plugs not firing

Check compression on all cylinders and spark with spark tester, if all that is good then it is fuel related

Salt water inside motor is bad on bearings and other shiny surfaces, so good luck with motor in the long run
 
I

ibuyre111

Seaman Apprentice
Joined
Sep 16, 2003
Messages
36
Re: Yamaha 1999 225HP 2 stroke OX66 Top two plugs not firing

I will check the compression and Spark.
Spoke to my friend and he mentioned that it might/could be a sensor that shuts off a couple of cylinders form firing. Some kind of fail safe. On this enging its the top plug on each side that dont fire.(V6) How does this sound to you? Running the enging to the ramp it would only go to about 1300 rmp's and seemed to run ok as far as smoothness goes.
Thanks for your response
 
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