Mercury 260HP piston part number?

[Dabbid]

just bought a 260, was told it has only 3 hrs sine new fogred wiseco pistons
removed one head and found the part number is 3137PS (wiseco)
looked it up on the net (http://www.wiseco.com/PDFs/Catalogs/MB07/Mercury.pdf) and found its listed as a any 2.5 from 150-200hp
i figured a high performance engine should have better stronger pistons
also the pistons were hitting the heads and the part number of the piston can be clearly read off the cylinder head, also all the ring grooves are flogged and allow movement of the rings, 1 ring is jammed from piston hitting the head, another has worked its way past the pin and was ready to get stuck in a port...
can someone tell me, should a 260 be using a different piston??
and if so, web page that lists it if possible?

[Jay Smith]

First you need to find out the deck height of your block and how much it has been milled to cause this contact. ALL 260 engines the pistons are .004" recessed into the block at true TDC and Drag motor pistons pertrude .004" at true TDC ( the reason the 260 comes with 3/4 MM head gasket and the gasketed drag with a 1 MM ) My guess is that your block has been decked very deep to straighten or true the sealing surface and some "builder" did not measure this lack of clearance and then finding this lack of clearance installed a thick enough gasket to clear the pistons travel at true TDC allowing for the decking and for rod stretch thus causing contact and you allot of money. If the piston contacts the head the top ring lan will become closed and that piston is now an expensive ash tray , I'd also check the rods for straightness as the contact may has bent them ...There are 3 thickness of Mercury 2.5 head gaskets , 3/4 mm, 1 mm , and 1 1/2 mm.. I'm sure one of the thicker ones will suit your needs and give you enough clearance for decking and rod stretch...

Good luck,

[Dabbid]

ok i understand all that, and thanks for answering so quickly, but wat about the pistons part number? is it a stock fishing piston that they have used? or are they the same like they are trying to tell me?

[us1]

They are forged and very heavy duty. I raced with them up to 10,000 RPM. The problem with them is the ring locater pin tends to fall out in a very short time.