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Winterization Of Gas Engines (MerCruiser)

Tips for your MerCruiser Engines

Taking time to winterize your boat correctly will insure that your boat is ready for dependable operation when Spring comes along.

Winterization should start with a good tune-up! Haul your boat and make sure the bottom and drives are cleaned of any barnacle or grass growth. The sooner you clean or pressure clean the boat after haul, the easier it will be. Run the engines on flush-muffs or a similar fresh water flushing system with good, clean fresh water for about 15 minutes each engine.

Note all gauge readings for proper operations and listen to the engine for any weird noises which may be an indication of existing problems.

Now is the time to address any mechanical problems that you might suspect. For example, if you hear a slight tapping noise and the engine really doesn't idle that great, your engine may seize up from rusty water that has leaked into the cylinders, especially if you ignore this problem till spring, The above example is actually VERY COMMON.

After you have flushed the engines on the hose it's a good idea to run some antifreeze through the system. PLEASE observe any environmental laws and safety concerns that may pertain to the coolant/antifreeze products that you are using.

Please note. The next step involves sucking an antifreeze mixture from a bucket using the suction of the water pump in the drive unit. If your water pump is not in perfect condition then the pump might not be able to draw the water from the bucket. This could cause an engine overheat condition which could lead to extensive (and expensive) damage. Take careful note if the hose is sucking from the bucket right away. If you get no suction then you have a problem with the hose, the flushett, or the water pump.

Get a 5 gallon bucket and mix up a 50:50 batch of antifreeze and water. It's good to use a short (6 foot long) garden hose that has the engine flushett at one end. Make sure the bucket end of the hose stays at the bottom of the bucket so that it doesn't suck air!

Note: The next step can be dangerous and it is recommended that an experienced MerCruiser mechanic perform the fogging operation as removal of the flame arrestor is necessary which can lead to burning, damage, injury and death. The flame arrestor on a boat is different from a cars air filter. A boats flame arrestor prevents backfires from exploding dangerous gases which can accumulate in the boats bilge. NEVER run a boat without an installed flame arrestor unless care is taken to prevent such explosions and fire fighting tools are close by and in good condition in case the need should arise to extinguish a gas or oil fire.

Following and knowing about the warnings above, remove the flame arrestor from the carb and have a can of fogging oil close by. Fogging oil now comes in spray cans. MerCruiser’s fogging oil is called Storage Seal and works great. You can also use a quart can of Marvel Mystery Oil if you like. It's a good idea to have a friend on the outside of the boat watching the garden hose and monitoring the fluid level in the bucket. This all has to happen smoothly!

NEVER run the engine without a water supply! Not even for 10 seconds!

Start the engine and let idle while observing the fluid level in the bucket. Before the bucket is empty, start to fog the engine but don't let it stall. Just before all the fluid is sucked out of the bucket, stall the engine by fogging at a faster rate. Once the engine has stalled, stop fogging. Reinstall the flame arrestor and plastic cover if supplied.

Some people prefer to leave the engine as is from this point. We recommend that the block and manifolds be drained. To drain the block, you will have to remove some type of block plug or open some type of petcock valve. MerCruiser has used a few different types of petcocks and/or plugs. Some look like brass wing-nuts with a drain hole in the center. Some are as simple as a brass plug. In either case, they will be located on the side of the engine block usually just behind where the motor braces bolt to the block.

These drains can be very difficult to remove sometimes. Also, when removed, they might be plugged with rust and will not drain. If the passage is plugged then take a thin screwdriver and ream the hole clean.

Next you will need to drain the exhaust manifolds. The bottom of the manifolds will sometimes have petcocks or brass plugs. Sometimes the manifolds wont have drain plugs and in this case you simply need to remove the water hose from the bottom to drain it.

The large water hose on the front of the engine should also be removed as it will puddle water even after the block is drained.

Get some good anticorrosion spray such as LPS#2 or Mercury's Corrosion Guard and spray the entire engine with a good coat while trying to avoid the plug wires and belts.

Make sure your bilge is clean as well as the rest of the boat.

Remove the battery, charge it up and store it in a well ventilated dry and safe area so it's not sitting on the ground.

Remove the drain plug so melted snow won't sink your boat on the trailer!

Remove the speedometer tube from the back of the speedometer and blow through the tube to expel any water in it.

Change your outdrive lube with whatever the factory recommends. If you had noticed ANY water in the old drive oil then take the outdrive in for service right away. Don't wait or your repair bill will be extremely higher due to the rusting of expensive parts.

Remove the prop and grease the prop shaft. Grease the transom zerk fittings and steering system.

Store the drive in the down position to prevent water from freezing in front of the prop and cracking your case. Also, it prevents the U-Joint bellows from getting distorted.

Your local marine store should have additives for your fresh water system. Drain the pipes and hoses. Also empty any sea-strainers On inboard engines.

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