This is a continuation of my other thread where my motor was hard starting, had low compression, didn't reach full power, couldn't maintain rpm and then it suddenly started working fine only to have my flywheel key shear while out on the water leaving me stranded.
I tore the head open and was shocked to see deeply gouged pistons, take a look:
http://imgur.com/a/OF7x3
1. What caused this to happen? The rings are not damaged, there was good waterflow from the discharge port and the inside of the motor looked clean.
2. Did I do this or a previous owner? Both cylinders were at 70psi previously, and after the key sheared I still read 70 psi on the top cylinder before doing the tear down.
I picked up a spare evinrude 9.5 powerhead with a blown head gasket, top cylinder was heavily carbonized while bottom was spotless. I attached the johnsons starter to the head and did whatever pulling I could which wasn't fast enough for a true reading, I got 60 psi top and maybe 35 on the bottom.
3. Would the blown head gasket account for such a pressure difference or could there be other issues?
I tore the spare head open and everything was in bad shape from the water leak, there was even sideways play in the connecting rods to the crank shaft by I'd estimate 15 thou. The cylinders have 'barreled' and become wider near the exhaust ports, the rings looked completely compressed through the intake ports and on the exhaust side they were bulging out. I don't have good measuring tools but the pistons measured about 2.308 to 2.311 of ovalling at the skirt and near the top was close to 2.300 dead. And the cylinders were about 2.308 at the top to about 2.318 near the ports, I think it would be safe to say that the average clearance is 10 thou. The pistons have dark corrosion marks all over but the cylinders still have a crosshatch.
To make matters worse, the evinrude design was slightly changed from the johnson and they have different carburetor systems and I may not have a complete carb for the evinrude or one that would work with the johnson face plate. The johnson head has deep lines running up and down so I think the only way to re-use that would be an expensive re bore + new oversized pistons, but other than that everything else on the johnson powerhead looks clean and shiny with minimal sideways play.
4. Would you bother trying to make a new motor out of these parts or do I need to buy new parts/ cheaper to buy another working motor? All of the seals are gone obviously.
5. Since I've got some dead pistons and a small lathe to play with, what about some exotic options like electroplating the pistons and turning them down to size?
I tore the head open and was shocked to see deeply gouged pistons, take a look:
http://imgur.com/a/OF7x3
1. What caused this to happen? The rings are not damaged, there was good waterflow from the discharge port and the inside of the motor looked clean.
2. Did I do this or a previous owner? Both cylinders were at 70psi previously, and after the key sheared I still read 70 psi on the top cylinder before doing the tear down.
I picked up a spare evinrude 9.5 powerhead with a blown head gasket, top cylinder was heavily carbonized while bottom was spotless. I attached the johnsons starter to the head and did whatever pulling I could which wasn't fast enough for a true reading, I got 60 psi top and maybe 35 on the bottom.
3. Would the blown head gasket account for such a pressure difference or could there be other issues?
I tore the spare head open and everything was in bad shape from the water leak, there was even sideways play in the connecting rods to the crank shaft by I'd estimate 15 thou. The cylinders have 'barreled' and become wider near the exhaust ports, the rings looked completely compressed through the intake ports and on the exhaust side they were bulging out. I don't have good measuring tools but the pistons measured about 2.308 to 2.311 of ovalling at the skirt and near the top was close to 2.300 dead. And the cylinders were about 2.308 at the top to about 2.318 near the ports, I think it would be safe to say that the average clearance is 10 thou. The pistons have dark corrosion marks all over but the cylinders still have a crosshatch.
To make matters worse, the evinrude design was slightly changed from the johnson and they have different carburetor systems and I may not have a complete carb for the evinrude or one that would work with the johnson face plate. The johnson head has deep lines running up and down so I think the only way to re-use that would be an expensive re bore + new oversized pistons, but other than that everything else on the johnson powerhead looks clean and shiny with minimal sideways play.
4. Would you bother trying to make a new motor out of these parts or do I need to buy new parts/ cheaper to buy another working motor? All of the seals are gone obviously.
5. Since I've got some dead pistons and a small lathe to play with, what about some exotic options like electroplating the pistons and turning them down to size?
But that is me.