cylinder wall and pistons

Pretty inexperienced, but learning a lot quick.
I just got done taking apart the motor and noticed that the top two pistons in the block had been scratched up a little on the sides. There was no damage to the rings. The top right piston or cylinder #1's piston top is somewhat melted or distorted. Both the top cylinders have a little scratching inside. I took the block to a machine shop to hone it out if possible. The guys believe its just part of the piston on the cylinder wall. If its not honeable is the next step to bore out the cylinders to .020 ? and should all cylinders be bored out or just the damaged ones?

This motor is a 1973 evinrude 135 hp

Another question is what could of caused this? Did the water pump stop working? Or did it run to lean? The carbs look in great shape. Is there a post that talks about the steps to checking to see if the water pump is working properly?

I appreciate any help and thank you for your time

Re: cylinder wall and pistons

You could well have dirty carb's. That 73, 135 was quite a hard running engine for it's time. Check the timing also when you get it back together. Also do the thermostat's, and water pump at that time.

Re: cylinder wall and pistons

You should check compression on all cylinders. If the undamaged cylinder show good compression, just bore the bad ones. You will need oversize pistons and ring sets.

Clean the carbs, replace the waterpump and set the timing to spec.

Re: cylinder wall and pistons

Most times people will say you need to do all of them at the same size/spec, but it is also said that it's perfectly acceptable to do only one cylinder and not the others, i.e. bore 1 and hone 2. If you look at Wiseco Pistons they offer other sizes other than the .020" over, in case yours is better or worse than that.
As previously said, do rebuild kits for the carbs and clean/rebuild them, and also do the water pump while you have the powerhead off.

Re: cylinder wall and pistons

The only accurate way to tell if the cylinders need boring is to measure them. The 2 with damaged pistons are a no brainer. Those will get bored. It's not likely that a 35 year old motor will still be in spec, especially with damaged pistons. Boring compared to honing isn't that expensive. The expensive part is the piston which you'll need 2 anyway.

As for the others, it's again not likely they will be in spec after a hone job. Even if the cylinders are only half thru the wear tolerance before it's honed you'll be at least 3/4 thru the wear tolerance after it's honed. And you haven't even talked aqbout piston skirt wear yet. No need to start with a fresh rebuild and have a motor that, at best, has 1/4 of the expected life left in half the cylinders.