1997 Challenger 1800 Piston Size

[spoutingrock]

My pistons are 81.89 - The pistons I'm seeing for sale state they are 82. Is the 82 referencing the cylinder size and the 81.89 piston is the appropriate size for that?

 

[mikidymac]

Why are you replacing the pistons?
81.89 is STD piston size.

 

[spoutingrock]

Why are you replacing the pistons?
81.89 is STD piston size.

 

[spoutingrock]

One of them is hammered on the top. Not sure why all the listings state 82.00 and larger. I've yet to find one for sale at the 81.89.

 

[mikidymac]

99.9% of the time you don't just install pistons and rings.
These watercraft ahve enough hours now that they need to be bored oversized and oversized pistons installed. I can almost guarantee that if you just slap in new pistons your compression is going to be low.

What happened to "hammer" one of the pistons? What let go? How did the cylinder not get damaged?
If nothing else you need to have a qualified machine shop measure the cylinders to see if they are still in spec before ordering new pistons.

Stock Bore diameter is 82.00mm
Minimum clearance is 0.100mm
Maximum Clearance is 0.200 mm
82.00 - 0.100 = 81.90 mm stock piston size.

 

[spoutingrock]

Not sure, I purchased as a project boat. The top is rough, could just be build up, but I figured it is worth spending the money to buy new ones. I appreciate the advice, I'll have them measured and honed if needed. Thanks.

 

[spoutingrock]

The cylinder walls and pistons seem to be in good shape. No rough spots

 

[spoutingrock]

Pressure test was 90 and 115

 

[mikidymac]

With those compression numbers it is worn out and needs to be bored with oversized pistons.
New STD pistons and rings aren't going to help.

 

[spoutingrock]

Thank you...will do.