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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4728
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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I have a 2001 Yamaha 200 HPDI engine that has a blown head

Customer Question

I have a 2001 Yamaha 200 HPDI engine that has a blown head gasket on the #1 cylinder. While replacing the head gasket, I noticed a small shiney piece of metal stuck in the top of the piston. I'm concerned that the piece of metal might be a piece of a ring. Is it possible to pull one piston without pulling the entire power-head ? Should I put it back together and see what my compression is with a new head gasket ?
Submitted: 6 years ago.
Category: Boat
Expert:  Jeff G. replied 6 years ago.
Welcome,this question may need more than a single answer. Please post back with additional questions on this at any time.
If there is metal in the top of the piston then yes the piston must come out. To be honest I haven't tried to remove just one piston on that particular engine. It is a horizontal reed engine so you should be able to do it. Remove the intake and go in from the front through the intake. then once the rod bolts are off push the piston out the back.
If you got water in the cylinder or overheated it is very likely a broken ring, particularly if it is a square shape.
Do not even try to put in together and do a compression test. The metal came form somewhere! If it is a broken ring and it catches in a port doing a compression test, it could severely damage the engine. If there are groves and scoring in the engine sleeve then I would go ahead and pull the entire engine apart.
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Customer: replied 6 years ago.
Jeff, I pulled the piston today and can't tell you how much I appreciate your answer. The piston and ring are damaged. I might be able to fix it, but it would have been disastrous to put it back together the way it was. Thank you very much !
- Chris
Expert:  Jeff G. replied 6 years ago.
You're welcome Chris, glad I was able to help.