Need advice 1972 evinrude lark 50 hp

[jfl1960]

Ok long story short I had to do some repair to my outboard, was given to me for free and ran but electronics were not working, had to pull power head due to some broken off bolts on exhaust cover and decided to pull head and take a peek, found both pistons in very good cosmetic condition, cylinder walls show minor scuffing and no ridge at all however the head has evidence of detonation on the top cylinder, normally there is damage to both the piston and head but in this instance I only see damage to head, here is my question would you guys reuse this head or scrap it and get a replacement (getting hard to find) is there any repair I could do to make it useable??????

 

[Boat Doctor1]

we dont know on damage??No PIX?? so---- id change the head!! Id also check the timing as thats an older engine & likely will have to be adjusted-due to our fuels now!! We all went thru this on the older engines when fuels werechanged in 80's!Maybe im the only one that remembers this here??HaHa--- are there any small parts (SMALL!) imbeded in tops of pistons? Top of piston ring lands all ok?? look =Closely!

 

[jfl1960]

we dont know on damage??No PIX?? so---- id change the head!! Id also check the timing as thats an older engine & likely will have to be adjusted-due to our fuels now!! We all went thru this on the older engines when fuels werechanged in 80's!Maybe im the only one that remembers this here??HaHa--- are there any small parts (SMALL!) imbeded in tops of pistons? Top of piston ring lands all ok?? look =Closely!

added pics, no damage to piston tops as far as I can see, didn't pull pistons but from the exhaust ports everything looks ok, I am thinking that the head was changed by previous owner or repair guy before I got it since ther is no visible evidence of detonation on the piston top, the motor ran strong just didn't charge battery and electric choke wasn't working, the sensor in the exhaust cover had failed, and the shifter diode was shorted along with the rectifier, anyway all sensors, diode, rectifier and the coils have been replaced with NOS, the CDI is only part I haven't replaced, going to test it and deal with that at a later date. Compression was within 10 PSI on both cylinders (actually 7.5 psi difference) when I tested it , wrote that in the repair manual but forgot to write in the actual pressure so cylinders compression is fairly equal.

 

[jfl1960]

No Title

Here are some pics if the pistons as seen through the exhaust ports, everything looks good to me what for you think.

 

[F_R]

Obviously, the top piston has been replaced at some time. The rings probably busted out of the top groove, causing that damage. They had a problem with that happening.

 

[jfl1960]

Obviously, the top piston has been replaced at some time. The rings probably busted out of the top groove, causing that damage. They had a problem with that happening.

Don't think so, to replace a piston the case would have to be separated, the paint is still intact at the case and gasket mating surface area and bolt heads, doesn't look like a socket ever touched them so I don't think the piston was ever touched, and if the rings had busted out I am sure the cylinder walls would have been scored, had a 2 stroke motorcycle that that happened to and it toasted a cylinder had to be bored. I found a head on ebay and am going to swap it out.