Pre-Winter Engine Detail

Give your boat's engine one last thorough cleaning.

All spring, summer and fall, your engine worked hard to provide your family with memories that will last a lifetime. Now it’s time to repay the favor and give it one last top-to-bottom cleaning. It’s even a good idea in southern states, because prolonged winter cold fronts can keep a boat out of the water for quite a while.

A heavy cleaning is especially critical if an engine is a few years old, because seals and gaskets start leaking and the resulting oil is a grime magnet, even if it’s behind an outboard’s sealed cowling. The biggest reason to clean an engine is to prevent corrosion, which gets its start in places that are neglected.

Unlike the business ladder, we’re going to start at the top and work toward the bottom. For outboards, this means the cowling — an engine’s protective armor and the part that is visible to everyone. It can take a beating during the season and deserves special attention. The first area of concern is the rubber seal that prevents water from entering — especially critical for boats in salt water, which is a corrosion jump-starter. If the seal is damaged in any way, replace it (now is a good time to do it, because there will be a backorder list when spring arrives). Use only factory replacements for this one and use contact cement to install it. If it looks good, clean it with mild soap and water and wipe it down with Aerospace 303 Protectant ($7.99), which also works on hoses, wires, vinyl seats and even Bimini tops.

For the cowling itself, use a water-and-soap mixture of Awlgrip Awlwash Concentrate 7324 ($27), which is an expensive but quality all-purpose boat wash that’s gentle, PH neutral and biodegradable. Star brite Boat Wash is only $8 and is in the same quality ballpark. Wet a new microfiber towel (a pack of 36 Zwipes is $17), which won’t scratch the clear coat, and gently wash the cowling. Rinse the rag, wipe the cowling again to remove the soap and dry it with a clean towel. For the last step, my favorite is Mercury Marine’s Cowl Finishing Compound. Not only does it make the cowl shine and protect it, but it can remove most scratches. Stay out of direct sunlight and apply it in small circles with a towel. Let the compound dry and use a clean towel to buff it. For areas that are


still scratched, apply a heavier concentration and spend more time working it in. A badly scratched cowling may require a buffer, such as the Shurhold Random Orbital Dual-Action Buffer ($160). This protocol works for the exterior of the lower unit too.

I am not a big fan of hosing down the engine block with water — and especially not with a high-pressure spray — because there are too many electrical items that can be compromised. Let the dirtiness of the engine block determine the cleaning regimen. First, disconnect the battery and remove it, especially if you intend to spray it with a low-pressure hose, and clean its exterior. Then, with a wire battery brush, clean the poles and connectors with CRC Battery Cleaner ($4) or replace them if they are worn. Don’t forget the battery tray, which can collect crud and some of the caustic overflow.

Next, use an assortment of brushes — toothbrush, bottle brush, longhandled brush with soft bristles and scrub brush — to attack the motor, dry, before introducing water or degreaser. You’ll be surprised by how much dirt and grime this step will remove. To keep things clean during the procedure, use a shop vac to suck up loose debris and keep it from falling down and hiding elsewhere.


Then fill a bucket with soapy water, dip a microfiber towel in it and wipe down the exterior of the block. Wrap the towel around the “wrong” end of a toothbrush, to get into the crannies, which transfers the dirt to the towel and keeps the surrounding area clean. Then go over the area with a damp towel to remove the soap. If rinsing is a must, protect electrical connections by wrapping them in heavyduty tin foil — and don’t forget to disconnect the battery.

If the engine is really grimy, use a degreaser, but first, lay down a giant diaper, aka an OilDri Absorbent HW Pad ($7), which can be found at an auto parts store. For sterndrives, use a bucket to collect the cruddy water from the bilge drain hole and dispose of it at a local recycling center. A tried-and-true product for this is Gunk Engine Brite Engine Degreaser Heavy Duty Gel ($6.49). Do not use the foamy version. Spray on enough for coverage, let it sit for a few minutes, work it in with the brushes and gently rinse, using a hose’s rain setting. Then dry it with a towel. If any water has pooled into recesses, use an air hose to clear it. A can of compressed air for cleaning a computer keyboard works great.

To protect the engine, spray the entire block with Yamaha’s Yamashield Rust & Corrosion Protectant ($9.49), which lubricates and protects all surfaces — even hoses and belts.

Next, pull the prop and use a towel to get rid of old gear oil that probably looks pretty grimy. Clean with degreaser if it’s really bad. Inspect the seals and remove any fishing line that may have gotten wrapped around the prop shaft (an inspection that should occur regularly during the season). Then re-grease the shaft and put the prop back on.

With that done, reinstall the battery, attach ear muffs and run the engine for a few minutes to heat-dry any water that may have escaped notice. Be sure to use ear muffs instead of the hose attachment found on many engines, because most engine manufacturers stipulate the hose outlet should only be used to flush with the engine off.

Now the engine is ready for the winterization process. And when the first boating day of next year arrives, you — and the engine — will be ready.