Q & A — April 2002
By Capt. Ken Kreisler
Torquing It Over
| Problems with a leaky oil pan, impeller pitting, an explanation of Total Base Number, and more.
have a 3.0L, four-cylinder in-line gasoline stern drive and do most of
my own maintenance. Lately I’ve noticed some oil leakage around the
oil pan. What could be causing this?
A.V., via e-mail
One is excessive torquing of the oil pan screws when a new gasket is installed, causing the gasket to be deformed and squeezed out. While the typical one-piece silicone rubber gasket includes metal spacers around each of the screws to prevent this from happening, over-tightening is still possible. You’ll have to replace the gasket. Refer to your engine manual’s specs on the correct torque for this application.
Two other possibilities are a defective gasket and one with insufficient contact or "crush" in certain areas to make a good seal. This is commonly caused by residue from an old gasket that was not removed during installation. Yet another cause could be deformation of the pan’s flange. If this is the case, you can usually straighten out the flange by tapping it lightly with a hammer. If not, a new pan will be needed.
Finally, the leak may be coming not from the pan but from either the front or rear main-bearing seals. The seals could be worn or defective, or if you’ve had any work done on the crankshaft, the problem could be mismatched surfaces. If this is the case, you’ll either need a new crankshaft or have to have yours machined.
a routine maintenance inspection of my cooling system’s freshwater
pump, I found the impeller blades to be pitted. What could have caused
this? T.L., via e-mail
Leaks are the usual
cause, so regular inspection to ensure hose and clamp integrity, proper
seating of all seals, and proper pressure cap and thermostat operation
is important. Flush your system regularly, following the engine manufacturer’s
directions, and always refill with approved coolant. You may also want
to check your engine owner’s manual for recommended coolant additives,
many of which contain defoaming agents.
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.