225 mercury pistons 4 and 5 pitted

[CPC]

I bought the offshore center console a year ago with a 97 225 carbed motor. Besides bad fuel mileage the motor seems to run well. Had 105 psi on all 6 cylinders and motor is very clean! The guy I bought te boat from said it had low hours due to being stored for 5+ years due to health issues. I got it cleaned carbs and changed fluids and plugs. Went on a dozen offshore trips and had the motor die on power last trip. Pulled the heads and 4 and 5 pistons have pits and what looks like pieces of metal stuck in the piston and head surface. All the bores looks good and still have good cross hatching. Is it ok to replace just the pistons and bearings and call it a day? Before I took the heads off motor still had 105 psi across all 6 cylinders.

Should I change all or fix what's broke and be on my way? I own and shop and build high performance turbo two stroke motors so am very familiar with 2 stoke motors. Only difference is my motors can't Leave me stranded 50 miles offshore. lol

Thanks for the advise.

Also who has the best deal on oem parts. I am a dealer with wiseco and see they have pistons for my application but don't think a forged piston would be the best for a stock motor.

[perfmarine1]

Sounds like you threw a ring.Ring dowel pin may have moved in and ring spun on piston then hooked a port. Pull piston and check,if so check all other piston pins. I have seen 1 inch piece of ring broken and compresson still good,and no damage to cyl. Stay away from wiseco forged ,go with stock merc,or pro marine pistons or others.

[CPC]

If they all check out ok would you just replace bad pistons or all?

On a side note I never go over 3800-4200 rpms due to fuel mileage on long range offshore trips. Wonder if I need to go wot every once in a while to blow out some carbon hold up? Not much outboard experience so looking for advise.

Thanks for reply.

[baddjonny]

Do the easy thing first check for a broken reed also check broken pecies with a magnet , rings or reeds or alum.

my 2
jon b

[CPC]

I've got the plate the reeds and carbs off and reeds look new and everything looks good. Can't see any bad bearings. I'll get the motor torn apart later in the week and see what the issue is.