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How-To Spring Commission
A Marine Engine

a tool boxPhoto courtesy Jensen Tools/Techni-Tool

Spring commissioning for an outboard motor or stern drive begins at the gear case, which happens to be the number one trouble spot.

As the vast sheets of ice begin melting away from the Great Frozen North eager boaters are toying with the notion of pulling their powerboat out of mothballs. With that in mind, the following checklist provides a step by step guide for spring commissioning outboard motors, stern drives and inboard marine engines for the coming season.

The first step in commissioning a marine engine is to review exactly what lay-up procedures were followed last fall. At the bare minimum, lay-up should have included draining and refilling both the engine's crankcase and the lower unit's gear case, fogging the engine to prevent rusty cylinders and storing the battery in a charged state in a warm, dry location.

Begin spring commissioning for an outboard motor or stern drive at the gear case, which happens to be the number one trouble spot. Gear cases should be drained and refilled at least every 100 hours running time, or at the minimum during lay-up. Even if you did change lower unit oil last fall, double-check to ensure you actually refilled it and that the gears aren't running dry.

Remove the bottom screw first, followed by the top. Drain old oil into a drain pan. Carefully examine the old lubricant for traces of water or broken bits of bearing and gear teeth. Water shows up as droplets, rust or a milky white froth. Be sure to rub some of the oil between your fingers, relying on your senses of sight and touch for detection.

If the oil comes out jet black and smelly, there's a very good chance the bearings and gears have been running red hot. Usually when you find burned oil you'll also find ground up brass and broken bits of gear teeth. Water indicates a leaking propeller shaft seal or shift rod seal. A few drops are OK, but require careful monitoring throughout the season. However, more than an ounce of water definitely requires professional repair as does any sign of metal bits or a burned smell.

Dispose of the old gear oil in an environmentally friendly manner then refill the gear case with the manufacturer's specified lubricant. The least messy method is to pump lube in from the bottom. Pump until oil just begins to trickle out the top vent hole. Then screw in the top plug and snug it down tightly so vacuum holds the oil in place long enough to screw in the bottom plug. Even more important than helping keep your hands clean, the top down method eliminates air pockets which could otherwise cause under filling a gear case.

Before buttoning up the gear case, count the old drain plug gaskets. There should be one for each plug. Be aware these gaskets tend to stack up on top of one another, leaving you with two gaskets one drain plug and none on the other. Such an unacceptable arrangement causes the gear case to leak oil and draw in water.

Prime and paint bare metal on the prop and lower unit housing to protect their surface from corrosion. When touching up, don't allow over spray on the sacrificial zincs or the coating will insulate them from electrolytic activity and render them useless as effective corrosion fighters. Note: Broken skegs and bent anti-ventilation plates are best left to the experts to repair.

- Continued -