Has anyone blown a 525 EFI Mercury piston?
 

Number 7 is gone to the ring lands, 130 hrs. Has anyone else had this problem? Mercury says it is rare.

Re: Has anyone blown a 525 EFI Mercury piston?
 

I have seen ringland failure in boosted hondas (thats the weak point of those little engines when you use force induction). If you have ringland failure chances are the cyl wall is scraped and needs to be honed. time for a rebuild if you wanna fix it the correct way.

Re: Has anyone blown a 525 EFI Mercury piston?
 

May have leaned out due to a partially clogged injector, might want to replace it before it goes back together.

Re: Has anyone blown a 525 EFI Mercury piston?
 

I would pulse check your injectors, they are pricey but you don't want them back in there if that's your problem. No warranty I assume? :rolleyes: :mad:

Re: Has anyone blown a 525 EFI Mercury piston?
 

Thanks for the replies. I do have a passport warranty, which they are honoring. I will be checking the injectors and fuel system. The motor only has 135 hours on it.
John B

Re: Has anyone blown a 525 EFI Mercury piston?
 

Had the same problem last year.I contacted merc before the warrenty ran out and they said the 6 qts of oil every 20 hrs was normal.I said then why is my other motor using 2 qts every 20 hrs. is one a 2 stroke and the other a four stroke.They wouldn't answer that.3 weeks after the warrenty ran out it let go on a poker run :mad: :mad: call on monday and after alot of i told you so they 2 day air me a new engine.The engine had 126 hrs on it busted in the #7 cylinder.

I know that this is an old thread, but for what it's worth, I currently have a situation of a twin engine 525 boat that has leaned out #7 cylinders in both motors multiple times. Rebuilding does not seem to be the answer.
Did you ever confirm what the fix is for this problem? Mercury is no help.

Only reason for a single cylinder to lean out would normally be a bad injector or injector driver in the ecm on that cylinder or possibly a bad injector pin connector or wiring. Replace those injectors and read the plugs on those cylinders after a light load to make sure those cylinders are not leaniing out again.

Best Regards,
Ray @ Raylar

fixx
 

years ago jasper engines did a study on the ford 302 engines, i know this is a boat engine but this may pertain to whats happening to yours..anyhoo they discovered that the pcv (oil) was routed to #8 cylinder and it would peel the ringland off the piston only on that cylinder..the fix was to plug the hole in #8 intake runner and drill and retap a hole in the center of the intake between all the cylinders..
Im not sure if theirs a pcv hose on the intake going to your #7 cylinder but i wonder if this would have caused your problem..if their is a hose going to that intake runner i strongly suggest to plug that hole and move it to the center of the intake.

The PCV inlet hose ona HP525efi engine goes intot the plenum on the port side of the engine in front of the intake runner opening for cylinder #5 not right at cylinder #7 so I don't think this is a PCV oil issue here.

Best Regards,
Ray @ Raylar