2001 225 Yam Piston Failure

[gardo]

my V6 225 Yamaha Saltwater series outboard's top port piston has melted, while the middle cylinder on the same side is worn on the exhaust port side. the bottom cylinder and the 3 starboard cylinders are in as new condition.

does any one know if there is a generic reason for this model to failure at this particular cylinder, or the likely causes for failure of just the 2 cylinders, one severe the other moderate?

 

[BruceAML]

Re: 2001 225 Yam Piston Failure

What type of oil and what spark plugs were in the engine?

 

[gardo]

Re: 2001 225 Yam Piston Failure

the plugs are NFK BR9HS 10
I have only used yamalube oil brought from my local yamaha dealer.
cheers

 

[BruceAML]

Re: 2001 225 Yam Piston Failure

Please post the complete model number and the country that the motor is from. In the US there are at least three 225 motors for that year. Have you looked at the oil injection lines for those 2 cylinders? Have you looked at the oil injection line check valves for those cylinders. Am I correct in thinking you have the oil pump and lines connected?

 

[gardo]

Re: 2001 225 Yam Piston Failure

Hi Bruce
the engine is from Australia
model is 225FETO
62J X 104418 T
All lines are definitely connected. I have not tested for blockages etc though
thanks for your interest

 

[rodbolt]

Re: 2001 225 Yam Piston Failure

a picture is worth a thousand words. however I cant convert your model number.
what is the engine displacement and is it EFI ?

 

[gardo]

Re: 2001 225 Yam Piston Failure

hi rodbolt.
I will have to check the displacement tomorrow. as far as I know there was only 1 2001 2 stroke saltwater series 2 engine on the market in OZ. obviously in the US you have far more of a market and product range!
the engine is efi.
thanks

 

[rodbolt]

Re: 2001 225 Yam Piston Failure

without seeing the piston I would make a guess of a lean fuel mix or possibly an overheat due to a loose pencil zinc in the block.
as all of the oil is mixed in the VST I would not suspect an oil failure, usually oil failures show up on the crank and rod surfaces as blueing.
check all the injectors and the O2 sensor carefully at reassembly. a defective O2 sensor can cause a lean piston burn above 4000 RPM.
it should be a 3.1L with CCS ign system.

 

[gardo]

Re: 2001 225 Yam Piston Failure

thanks, I will check them all during reassembly