Learning how to winterize a 5.0 Volvo Penta is the only way to make sure your boat survives the freezing months without a massive repair bill waiting for you in the spring. If you've spent any time on the water, you know that water expands when it freezes, and if that water is trapped inside your engine block, it's going to find a way out—usually by cracking the iron. Nobody wants to start their summer by shopping for a new long block because they skipped a couple of hours of maintenance in October.
The 5.0-liter Volvo Penta, whether you've got the carbureted GL model or the fuel-injected GXi, is a workhorse, but it isn't invincible. The good news is that you don't need a degree in marine engineering to get this job done. With a few basic tools, some fresh fluids, and a bit of patience, you can do it yourself and save a few hundred bucks in shop labor.
Start with the fuel system
Before you even think about draining water, you need to deal with the gas. Modern fuel, especially the stuff with ethanol in it, doesn't like to sit around for six months. It starts to break down and turn into a gummy mess that will clog up your injectors or your carb.
First, head to the gas station and top off your tank to about 95% full. Leaving a little room for expansion is good, but you want to minimize the amount of air in the tank to prevent condensation. Add a high-quality fuel stabilizer—something like Sta-Bil Marine is a classic choice. Once the stabilizer is in, you must run the engine for about 10 to 15 minutes. This ensures the treated fuel actually makes it through the fuel lines and into the engine itself. If you just pour it in the tank and shut the boat off, the fuel sitting in your engine is still "dry" and unprotected.
Changing the oil while it's warm
While you're running the engine to circulate that fuel stabilizer, you're also warming up the oil. This is the perfect time to do an oil change. Cold oil is thick and stubborn; warm oil flows out much faster and carries more of the sludge and contaminants with it.
Why change the oil now instead of in the spring? Because used oil contains acids and moisture that are byproducts of combustion. You don't want those sitting against your bearings and internal parts all winter. Use a vacuum pump to suck the oil out through the dipstick tube—it's much cleaner than trying to reach the drain plug in a cramped bilge. Swap out the filter, rub a little fresh oil on the new gasket, and fill it back up with the manufacturer-recommended weight. Usually, for a 5.0 Volvo Penta, you're looking at a high-quality 30W or a synthetic blend designed for marine use.
Draining the cooling system
This is the most critical part of how to winterize a 5.0 Volvo Penta. If you mess this up, the rest doesn't matter. You need to get every drop of "raw" water out of the engine.
Most 5.0 Volvo Pentas have a series of drain plugs. You'll usually find two on the engine block (one on each side) and one on each exhaust manifold. Look for those blue or black plastic wing-nut style plugs. Unscrew them and let the water drain into the bilge.
Pro tip: Don't just assume it's empty because water stops flowing. Rust flakes and sand often settle at the bottom of the water jackets and plug up the holes. Get a small piece of wire or a thin screwdriver and poke it into the drain holes. You'll often be surprised when a whole new gallon of water comes rushing out after you clear a tiny blockage. Also, don't forget to disconnect the large hoses at the bottom of the circulating pump and the sea water pump to let them drain out too.
The "Pink Stuff" (Antifreeze)
Once the water is out, a lot of guys just leave it dry. While that can work, it leaves the inside of your engine open to oxygen, which causes internal corrosion. It's much better to fill the system with marine-grade propylene glycol (the non-toxic pink stuff).
There are two ways to do this. You can use a "muff" kit on the outdrive and let the engine suck the antifreeze in while it's running, but that's a bit risky if the thermostat doesn't open fully. The more reliable way is to manually pour the antifreeze into the hoses.
Remove the top hoses from the thermostat housing and use a funnel to pour the pink stuff directly into the block and the manifolds until you see it coming out of the drain holes (which you should have put back in by now). This guarantees that every corner of the cooling system is protected. Make sure the antifreeze is rated for at least -50°F; don't use the cheap automotive stuff, as it's toxic to the environment and can damage your seals.
Fogging the engine cylinders
To prevent the piston rings from sticking and the cylinder walls from rusting, you need to "fog" the engine. If you have a carbureted 5.0 GL, this is easy. With the engine running (and water/antifreeze flowing), spray marine fogging oil directly into the carburetor throat until the engine starts to cough and emit thick white smoke. Then, shut it off.
If you have a fuel-injected 5.0 GXi, don't spray fogging oil into the intake. It can mess up your sensors. Instead, the best way is to pull the spark plugs and spray a quick burst of fogging oil directly into each cylinder. Give the engine a very quick crank (don't let it start) just to spread the oil around the cylinder walls, and then put the plugs back in. This keeps everything lubricated and ready for that first turn of the key in May.
Checking the outdrive and gear lube
You can't forget about the back of the boat. The Volvo Penta outdrive is a precision piece of machinery, and it needs love too. Trim the drive down so it's in the vertical position. This allows any water trapped in the housing to drain out so it doesn't freeze and crack the casting.
Check your gear lube by cracking the bottom drain screw just a little bit. If clear, green, or blue oil comes out, you're fine. If you see "chocolate milk," you have a seal leak, and water has gotten into your gear housing. If that's the case, you need to drain it all and get those seals replaced before the water freezes and ruins your gears. Even if the oil looks okay, it's usually a good habit to change it every year anyway.
While you're back there, check the rubber bellows. These are the accordion-looking boots that keep water out of your u-joints and shift cables. If they look cracked or "checked," plan on replacing them before the boat goes back in the water. A leaky bellows is one of the fastest ways to sink a boat.
Final battery and bilge care
The last few steps are all about the small details. Disconnect your battery and, if possible, take it home and put it on a trickle charger in the garage. Batteries hate the cold, and a dead battery that freezes is usually toast by spring.
Clean out your bilge and make sure the drain plug is removed from the transom. You want any rain or snow melt to be able to run straight out of the boat rather than pooling in the bottom and potentially reaching your starter or oil pan. Give the engine a quick wipe down with a rag soaked in a little WD-40 or a corrosion inhibitor spray to keep the exterior parts from rusting in the damp winter air.
That's pretty much the gist of how to winterize a 5.0 Volvo Penta. It feels like a lot of steps the first time you do it, but once you get a rhythm down, it's just a Saturday afternoon project. Taking the time to do it right means you can sleep easy when the temperature drops, knowing your boat is safe and sound. Come spring, you'll be the first one back on the lake while everyone else is still waiting for the mechanic to call them back.