mercury 900 90hp metal flakes on spark plug?????

[lhart1]

2 plugs have a coating on them with what looks like metal shavings. Boat was running good for a few hours then lost power and wouldn't start.

 

[sawblade723]

Re: mercury 900 90hp metal flakes on spark plug?????

Does the metal flakes look like melted aluminum? Sounds like you have scorched some pistons.

 

[rodbolt]

Re: mercury 900 90hp metal flakes on spark plug?????

another blown powerhead.
when was the last full water pump install?
the pistons overheated and the crowns ate off.
its called throwoff.
test the compression on all 6,all should be within 10 PSI.