Re: OMC 3.0 Piston Slap? a common problem?
Manufacturers use all sorts of techniques to reduce friction and raise fuel economy. applying a coating to pistons is just one of those techniques. Any coating takes up space so if that coating wears off a bit the piston to bore clearance opens a tad and during warm up an engine can exhibit piston slap. My Yukon with 111,000 slaps for about 20 seconds from about 30 seconds after cold startup. It then quits almost immediately. It uses no oil and is used as a tow vehicle.
I already covered several reasons for piston slap but additional reasons are an engine that may have been assembled with a combination of high-limit and low-limit parts. That means pistons at the small end of the diameter tolerance were installed in a block bored to the high end of the diameter tolerance. It is called a build-up of tolerances and applies to anything mechanical. It is the thrust of the piston against the cylinder wall as the piston fires that causes the slap and it makes no difference whether an engine is a pancake design, in-line, 60 degree or 90 degree "V". The only time the piston does not have side thrust is when it sits exactly at TDC or BDC which is when the piston, rod, and crank throw are all perfectly in alignment.
