Blown Piston ? Sleeve or Bore?

[optech]

I have a 1998 Merc offshore 200hp carb engine. The motor was blown due to an oil pump failure . # 4 piston is blown along with the rod and portside cyl. head the engine has a sleeve block not chrome. The # 4 cylinder is scored. I do not know how deep. I found out that OEM pistons are only available for this model at .015" over this may not be enough of an over bore to get rid of the scoring. After market (Wiseco) pistons are available at .020", .030" and.044" is it OK to overbore more than the OEM .015". Should I not overbore and go for a sleeve and standard size OEM piston & rod. The rest of the engine is perfect. The motor has less than a season on it. A friend gave it to me he was reimbursed for it by insurance and it was stored in his place of business for 6 years (no rust the motor is like new except for the broken parts) I also need controls and a wire harness.
PS
How do I disconnect and bypass the auto oiler system and mix oil and gas I think it is a safer bet.

Many Thanks

Joe M (optech@optonline.net)

 

[andy6374]

Re: Blown Piston ? Sleeve or Bore?

Not sure about the overbore more than the OEM .015". I suspect it is fine as Wiseco makes the pistons.

However an oil pump failure wouldn't have been my guess, why is it yours? The oil pump pumps oil equally to all cylinders, so if one failed, all the cylinders should have been damaged. Due to the selectiveness of the damage I bet you have a lean jet in the carb. I figure out the cause for sure before putting back together. A blown piston is the result not the cause.

 

[optech]

Re: Blown Piston ? Sleeve or Bore?

Not sure about the overbore more than the OEM .015". I suspect it is fine as Wiseco makes the pistons.

However an oil pump failure wouldn't have been my guess, why is it yours? The oil pump pumps oil equally to all cylinders, so if one failed, all the cylinders should have been damaged. Due to the selectiveness of the damage I bet you have a lean jet in the carb. I figure out the cause for sure before putting back together. A blown piston is the result not the cause.