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

The first step in commisioning 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 gearcase, 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 gearcase, which happens to be the number one trouble spot. Gearcases 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 gearcase 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 underfilling a gearcase.

Before buttoning up the gearcase, 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 overspray 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-cavitation plates are best left to the experts to repair.

Before you install the propeller, inspect its blades for nicks and dings. Otherwise the wheel will vibrate and cause premature wear to shafts and bearings. Straighten dings with a rawhide mallet. Minor nicks (smaller than your thumbnail) can be filed smooth. Remove as little metal as possible to prevent unbalancing the wheel. Examine the propeller's shock absorber bushing for cracks or otherwise obvious damage.

Coat the propeller shaft with corrosion fighting, marine grade grease, then re-install the propeller using a new cotter pin. Check water intake and discharge ports for obstructions.

Examine the sacrifical zincs noting they should be replaced before they've corroded away to less than half their original size. Regardless of whether or not an individual zinc needs replacing, remove it and make sure there's good metal to metal contact between the zinc and its mating surface. Otherwise it won't work its magic. Before replacing, coat the bolt's threads with anti-corrosion grease.

Inspect the powerhead for loose, missing or damaged parts. Lay a wrench on every bolt, including engine mounts and manifold bolts, making sure none have vibrated loose. Don't forget the steering linkage! Tighten as necessary, but do not overtighten. On outboards, be sure to check the hold down bolts that secure the motor to the transom. Tip: An outboard motor's loose and dangling hood rubber can be glued back in place with weatherstrip compound.

Last fall during lay-up, you wisely loosened the alternator and water pump drive belts. Before snugging them up again, first inspect for cracks, checkering or frayed edges. Replace as necessary. Correct tension allows for about 1/4 to 3/8 inch play measured midway between the pulleys.

Similarly, visually inspect cooling system hoses. Checkered or cracked surfaces indicate replacement is necessary. Firmly grab each hose. Any that have lost resiliency and become hard and brittle, or are have bulged require replacement. Also check the hose clamps replacing any that have corroded or been otherwise damaged. Lay a screw driver on each one making sure vibration hasn't loosened them.

Last fall you mothballed the motor by fogging its cylinders with a sticky, preservative oil that resists sliding off the cylinder wall's polished surfaces. Come spring, this oil must be blown out of the combustion chambers. To do so, remove all of the spark plugs. Throw the throttle lever wide open. Crank the engine for about a minute, staying clear of the oil vapor that blows out through the sparkplug holes.

Hint: Before cranking the engine, open the fuel line valve so that cranking the engine not only clears the fogging oil, but also pre-lubricates bearings and fills the carburetor float bowl.

Before re-installing the sparkplugs, check the insulator and gap. Fouling should be removed. Even better, replace the plugs outright. Always replace spark plugs in complete sets following the manufacturer's recommendations for heat range and combustion chamber reach.

On outboard motors, squeeze the rubber fuel lines, paying very close attention to the length of hose nearest the engine where heat accelerates deterioration. If a line feels mushy or bloated, or exhibits cracks, replace it. Also pump the primer bulb making sure it works freely.

Before installing starting and deep cycle batteries, top off each cell with distilled water. Tap water is not acceptable because its mineral impurities shorten battery life. Next, bring the batteries up to full charge.

Grease the battery posts and cable terminals with a thin coating of grease to help prevent corrosion. Similarly, you're about to protect the rest of the boat's electrical connections. Choose a favorite brand of moisture-displacing lubricant, then liberally spray terminal blocks, circuit breakers and wiring harness connectors. Applying spray dries out moisture and reduces the possibility of future corrosion. This is also a good time to replace blown fuses.

If the fuel tanks were topped off last fall and the gasoline stabilized, nothing needs to be done in the spring. On the other hand, partially-full tanks have likely attracted condensation. Remove any possibility of water in the gas by dosing the fuel with an appropriate additive such as Heet.

One way to determine whether there's water in the gas is to drip a small amount into the palm of your hand. If all of it evaporates it's gasoline. If little beads of water dot your hand, it's contaminated. If your fuel supply is consistently contaminated by water, installing a fuel/water separator can eliminate the hassle of dumping fuel dryer into the tanks.

Once the boat has juice, switch on the bilge pump and engine compartment blower, making certain they're operational. On outboard and sterndrive powered rigs, run the power tilt and trim up and down several times. Then check the lift pumps fluid reservoir, topping off as necessary. Turn on all the running lights and see if any of the bulbs are burned out. Honk the horn, making sure it hasn't corroded itself to death.

Last fall you removed the drain plugs from the engine block and heat exchangers and stored them in a plastic baggy along with the ignition keys. Reinstall the drain plugs.

On inboards and sterndrives, check the coolant, making sure it's topped off and the blend exhibits adequate anti-freeze protection. If the coolant is more than two years old, drain and refill. Otherwise there is a good chance the solution has lost its corrosion fighting ability.

Check the steering. (If your rig has power steering, conduct this test with the engine running) Turn the wheel hard to port, then to starboard. It should traverse freely.

Next run the throttle up and down to make sure it doesn't bind. Shifting into forward and reverse gear should lock up the prop tightly. It should not ratchet, otherwise the shift mechanism needs adjusting. In neutral, the propeller should free-wheel.

Shift and throttle cables should be replaced if they bind or have cracked outer casings. To determine correct length on replacements, measure from the control box to the stern then across the transom to the motor's connector. Add three feet to that length in order to form a loop that will prevent binding when the motor is cranked from port to starboard or vice versa.

The final step in commisioning a rig is to test run the engine so you locate problems dockside, not offshore. Once the engine's running, take it easy until it's reached operating temperature. Letting it idle for several minutes circulates fresh oil throughout and lets the seals soften. In the meantime do keep an eye out for potential problems. Check the oil filter base for leaks, and tighten as necessary. Also keep an eye out for coolant leaks, paying particular attention to the drain plugs you just reinstalled. Steam vapor is a clue you're loosing coolant.

Monitor oil pressure and temperature gauges as the engine warms up. Wherever applicable check the water pump discharge that indicates raw water/coolant flow. If you're not sure whether your engine is overheating, carefully lay your hand on the cylinder head, being careful to avoid a potential burn or shock from the high tension leads. The head should be hot, but not scorch your hand. In other words, you should almost be able to lay you hand on it. However, if it's as hot as a griddle, and sizzles droplets of water, immediately shut down the engine.