175hp sportjet

[blen]

I have a 175hp sportjet with two scored cylinders that the machinist says needs to be bored.The other four look good and the motor only has 75hrs on it.Is it acceptable to run two oversized pistons and would it be possible to resleeve the two holes and run all the same size pistons? What would be best? THX

[props4u2]

It is normal to see 1 or more over size pistons in o/b engines & the rest std. size. New sleeves can be installed if you want all std. pistons. If it is a carb engine, be sure to install the next size larger jets in the bored cylinders.


Lee

[Raceman]

Running 2 oversized pistons is fine. I'd rather have it than a resleeved steel block when it isn't necessary otherwise. My 175 Sportjet stuck a piston when the crap plastic oil pump gear that Merc uses took a dive at 8 hrs. on the meter. I just bored the one hole and didn't see the need to re jet.

[blen]

Raceman the infamamous plastic oil pump gear caused my woes also.THX for the reply. I wonder what else I should do while I have the motor apart.Should I hone and rering the other four holes? (The oil pump is already in the garbage) As I stated in My first post the motor only has 75 hrs but I would like it to be as reliable as possible.I'am not looking to get real good at tearing the thing down THX.

[Raceman]

One thing I'd caution you about is re-torquing the exhaust chest bolts. I was doing mine with a ft lbs torque wrench and dividing by 12 (less a little bit) About the 3rd bolt and BANG......... all the threads pop out on one bolt........ looked like a heli coil pulled out, but it was just the threads. HalfFast gives me hell for doing it with a Ft/lb. So I go buy a helicoil set in that size and an el cheapo click type inch lb. torque wrench at Auto Zone. About 2 bolts later, dead to factory spec and BANG........ another set of threads. HalfFAst gives me hell about using a cheap torque wrench, So........... I go get a Snap on. Guess what............. BANG AGAIN. So now I've got 3 different torque wrenches, pullling on a bolt to factory spec, and 3 helicoils in different holes to show for it.

Back off 5 in/lbs.