Black horizontal ring in on cylinder wall

[zigbat]

OMC 2.3 Block.. has overheated but didnt seize or anything, head wasnt cracked , had it rebuilt
The thing is the #4 cylinder has a ring in it its not perfectly straight line its jagged making me thing its an indication of a crack that let some crap in and rubbed it into the wall, but ya cant see an actual crack and it feels smooth... and it goes all the way around so i would think it would fall apart if it was a crack..
everything i can find about cylinder inspections is about scratches that are vertical.. this looks like someone took a broad tipped pencil and drew a line all the way around the cylinder..
Thought about rubbing on it with some 800 sandpaper to see what happened but i have never seen or heard about anything like this and cant find any info online.
At this point i figure Black line = bad no matter if i can identify its cause or not, but if the block isnt cracked and is usable i wanna d that..
Thought about putting a 1/4" sheet of plexiglass on it and bolting it down with some sealer and pumping like 80 psi or so nto it and let it sit awhile and see if it holds air... I dont know what is involved for a shop to check it but i have too much money in a 4500 dollar boat already so trying to get it running reliably so i can keep it or at least have the option to sell it for anything but salvage..

 

[Scott Danforth]

, had it rebuilt

you had the block bored and honed and new pistons, rings and bearings?

if so, the machine shop should have checked with dye penetrate

could be a crack from overheating. I would get some crack penetrating dye, cleaner and developer and follow the directions

if you havent re-assembled yet, take the block back to the machine shop

they will eat the cost of the bore/hone, you will have to pay for another pinto/ranger block core (about $100)

 

[zigbat]

Havent had the block to the shop, just removed the head and found the ring, I'm pretty sure its a crack, I cant come up with a better explanation..
No matter how ya dice it, I think Black ring = bad since it is supposed to be shiny everywhere...
I dont know what a shop would charge to confirm that black ring = bad but I think it would cover the cost of just buying a running pickup motor to have rebuilt instead..
I was hoping somebody would come up with something like Black Ring < Good but block is usable.. You dont sound to confident that may be the case.. .
I have already (almost) decided to call it bad and i gathered all the parts to put away untill before next season and buy a truck motor this was a last ditch effort to see if anyone had seen a similar thing and knew for sure what would cause it outside being a crack.. I am not confident there is another explanation..

 

[Scott Danforth]

I suspect a crack as well, especially since you stated it is jagged in appearance. wouldnt even waste the $100 dye test on it.

personally, if it was my boat, I would pull the pinto motor out and re-power with a 4.3/alpha mercruiser combo.

 

[zigbat]

you have recommended that to me before.. I am looking around for one with the drive..
Let me ask you ths, If i regeared the small hub cobra I have (21:21 13:26) to the 4.3 gears 21:19 14:26), I would have to only buy two gears it looks like
would that work as well as the matched outdrive or does the small hub make any difference (or anything else make a difference)
and how can ya tell the difference between a 125 hp, 175 hp and 205 hp 4.3L at a glance?

 

[Scott Danforth]

the 205 and 220 hp 4.3's are 4-barrel carbs or MPI fuel injection

you can get a mid-90's boat with a rotten hull and a working 4.3 and alpha drive for about $3k. pull the motor/drive, use that in your boat, scrap the hull, sell the trailer, sell your OMG parts and you will be out about $1500

 

[zigbat]

check this out... Found it just now...
https://salem.craigslist.org/bpo/d/omcmercruiser-43-v6-complete/6295582558.html

I'm thinking about taking a trip to salem...
This is what I want right??

 

[Scott Danforth]

you get the whole boat plus everything, for $800. I would hear it run, however that would be a good deal.

if you decide you want more power after that, you can swap to vortec heads and a 4-barrel intake/carb for about $500