Mercury Disappointment

[Dave R]

Originally Posted by Kamper

I'm not saying you were abusive but new motors do have a break-in period where the builder advises running at moderate engine speeds. Some operators get through this run-in period by letting the motor idle at the dock or on the hook, or hose. 15 hours would be well within most recommended time frames .

Running at idle would be a terrible way to break in an engine. The piston compression rings are designed to allow combustion gases behind them and these gases push the rings against the cylinder walls on the power stroke, creating a seal. You want high pressure in the cylinders to get the rings to seat properly. At idle, there's very little pressure and the rings won't seat, but they will soften the sharp ridges off the cross hatch pattern from the final honing and that will keep the rings from ever seating. Engines need to be loaded to break them in.