135 OPTI piston help

im helping out a friend of mine with a rebuild on a 2003 opti saltwater series he just purchased.
the powerhead needs two starboard pistons(#859563t 4).we are having trouble locating the right p# that corresponds to the mercury p# for this particular engine.it is listed as a 2.5 dfi motor so are the 135,150 ,and 175hp pistons the same?if so,where does the horsepower increase come from?i know there are ALOT of guys on here that know these black motors inside out,so help out my ADHD buddy please as he just does not have the patience to sit down and research these things!

the Ecu and and there is a restrictor located on the air handler.i would have to look up the exhaust to see if its the same.

are the pistons the same?

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Originally Posted by skeeter91

are the pistons the same?

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yes the pistons are the same

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Originally Posted by boatdr72653

yes the pistons are the same

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the exhaust tube is the same as well.i went back through several serial groups to be for sure your engine was covered.all were same 135 to 150.unless somebody knows something I'm missing it's just the ecu and restrictor.the restrictor is as easy to remove as the ecu.hope this answers your question.i believe this information to be correct.you can look for yourself on boats.net.compare your 135 to the 150 your same serial group

thanks a bunch for the help.i have crossed alot of numbers on that site,it is a real useful tool for crossing numbers.do you think it is worth removing the restrictor if we are going to keep the 135 ECU?