An In Depth Look
From Jim Shepard, Your Guide to Powerboating. About.com

Soon, many boat owners, myself included, need to face the ugly fact that it will be necessary to winterize our boats against the icy blasts of a long winter in the Northern climes. Whether to suffer the slings and arrows of outrageous labor costs or do it yourself becomes a hot topic of debate. The discussion always comes down to this question: “Is the money you save this fall worth the risk of facing major damage next spring, in case you missed something?” It is my opinion – and I have an opinion on just about everything – that unless you really know what you’re doing, leave it to the pros! That said, I have a few reminders for those of us who are still going to do it ourselves.

Engine Winterization

1. Change the oil and filter.
It doesn’t matter if the engine has 5 or 105 hours on it since the last change. Today’s oils do not wear out, but they do get contaminated with dirt, combustion residue and acid. Leaving any of these things to settle on your engine’s moving parts, during the winter, is a bad idea.

Run the engine until the oil gets warm, thus suspending all of the “bad stuff.” Next. drain or pump it out, change the filter (including a new gasket), and put in the new oil.

Caution: Do not over fill, as too much oil will cause all kinds of problems. Check the owner’s manual for the manufacturer’s recommendations on the type and amount of oil to use.

2. Add fuel stabilizer to your fuel and top off the tank. Run the engine long enough to ensure the stabilized fuel has reached your carburetor or injectors.

3. Fogging: Fogging is accomplished by feeding a rust preventative lubricant through the carburetor or throttle body, while the engine is running at about 1000 to 1200 rpms and is thoroughly warmed up. Very slowly pour in the lubricant until lots of blue smoke comes out of the exhaust. This method will thoroughly coat the cylinders, rings, valve seats and valve stems. DO NOT pour the liquid in too quickly or you will “choke” the engine, causing combustion knock. Besides, too much liquid added at one time can cause hydrostatic lock in the cylinders and DESTROY your engine! Follow the fogging oil manufacturers’ instructions!

4. I/O Engine: If you have an I/O (inboard/outboard), drain the lower unit and check it for any sign of water contamination (a milky color instead of clear) and/or any metal shavings (gear damage). If all looks good, refill the unit with new grease. If not, get it repaired now!

5. Cooling Systems: Preparing your cooling system for winter depends on the type of system you have. Remember, always follow the manufacturers’ instructions and use the following procedures only as a guide.

Raw Water (Direct) Cooling System. Proper winterization of a raw water system should start with a thorough flushing of the system with fresh water running through the engine while it is running at normal temperature. This part is REALLY important if you have been running in salt water.

First, disconnect the intake hose from the thru hull fitting and attach it to a garden hose. Note: if you have an I/O, you’ll need a set of “ear muffs” to attach to the water intake on the lower unit. Remember, running an I/O for even a few seconds without water will destroy the impeller in the water pump!

After flushing, drain the engine block, manifolds, risers and oil coolers by opening the petcocks on the various units. After all the water has drained out, close each petcock. Disconnect the garden hose from the intake hose and place the intake hose in some environmentally friendly (“Pink”) antifreeze and drain the fluid by running the engine. When the antifreeze starts coming out the exhaust, shut the engine down.

Now here’s a biggie: Don’t forget your engine has a thermostat! This whole procedure must be done with the engine totally warmed up and the thermostat OPEN. A closed thermostat will not allow the antifreeze to enter the block or heads. This means the antifreeze will go through the manifolds and out the exhaust, leaving the block and heads completely void of any antifreeze. If this happens, next spring you may have a cracked block or head and find it necessary to buy a new, very expensive engine. One of my sons stores many boats over the winter, most of which are laid up by the owners themselves. Each spring, one or two of them fall victim to this oversight.

Closed (Indirect) Systems: These systems do not require annual draining and flushing of the closed part of the system. HOWEVER, the open part of the system DOES require the same procedures of flushing, draining and antifreeze infusion as previously described in the Raw Water (Direct) System.

Finally, some additional thoughts:

* If any of the above instructions seem to be confusing or over your head, that’s probably the best clue that you need a professional to winterize your engine.

* Also remember, if a pro lays up your engine and something goes wrong, next spring he has a problem. If you’ve done your own work, you have a problem!

From Jim Shepard, Your Guide to Powerboating. About.com