Piston clearance

**tony nc** · 11-16-2002, 11:42 PM

What clearance would you recomend for a steel sleeve 260 motor running mahle pistons? Thanks Tony

**QUICKSILVER** · 11-17-2002, 12:06 AM

I don't know for a 260 but for a 200 2.5 with steel cyl. bores, the service manual gives .007 for a new block and piston.

**KRAAZYBOAT** · 11-17-2002, 09:15 AM

So bore size is 3.502 to 3.503 for a steel bore motor. And i guess i tend to stay to the 3.503 mostly. Others jump in on this. Dave

**QUICKSILVER** · 11-17-2002, 09:29 AM

For a factory steel sleeve motor, bore size is 3.501, piston is 3.494 +or- .001

**MTCM** · 11-17-2002, 09:56 AM

From the 2.5 Hi-Performance Service Manual..............................................

**MTCM** · 11-17-2002, 09:58 AM

More Specs.................

**Jay Smith** · 11-17-2002, 10:00 AM

What ring are ya gonna run on that steel bore with that Mahle piston Tony ? The gold rings even with a diamond slick hone have not lived long for us. If the keystone angle cut is the same and the ring is 1 1/2 mm on your suspect Mahle you can use the Pro marine ring for a steel bore BUT the end gap slot has to be cut to accept the locater pin in the middle of the ring lan ! I use John Marles( US1 ) to cut my rings if I have to convert a side pinned to a top pinned ( Or Mahle type positioned pinned piston ). Just trying to save ya some grief that we have found to be in the future with anything other than the set up I just sited !

Good luck !

**us1** · 11-17-2002, 11:09 AM

I use .007 on any Mercury 2.5 piston in a steel bore and .0085 on a Wiseco. This is for motors running no popet and no thermostats.

**tony nc** · 11-17-2002, 12:26 PM

Jay, I have been useing the gold rings. They have done ok, but do need alot of breakin time. I didnt post that to start with because I didnt think there was anything else to use..lol.

John, I would take it that .007 would be 3.501. Going with a 3.494 piston size.
On a motor like this would you change anything about the cooling. as in the water diverters around the cylinders. changing the size of the water restricters in the heads..ect.. Thanks. Tony

**us1** · 11-17-2002, 12:33 PM

I measure each piston before setting the final bore size but if your piston is 3.494 then 3.351 will do fine. As long as you are running 1/8 stainless fender washers in the heads the cooling will be fine. Was the water pressure 15 lbs. minimum at WOT before.