You’ve kept your marine diesel mains and generators running well all season, and now the grip of winter is near. But your work isn’t done. To make sure these engines perform well next season, take these six important steps to properly winterize your diesel systems before giving them a long winter’s rest.
1. Fuel Management
Unless properly treated, diesel — especially the newer bio-diesel and low-sulfur fuels — can grow stale and prone to bacteria and fungal infestations while in storage, resulting in sludge and sediment that can plug filters, create starting problems and damage engines. Also, an empty fuel tank invites condensation, and over time this results in water collecting in the bottom of the tank, posing a serious problem for diesel engines. To help prevent any of these maladies, fill up before long-term storage. Then treat the fresh fuel with a diesel biocide/stabilizer such as ValvTect BioGuard Plus 6 ($24.99/32 ounces, defender.com). After treating the fuel, install new primary and secondary fuel filters, and then bleed the fuel lines to eliminate any air pockets.
2. Fresh Oil
Used diesel engine oil contains acids and other contaminants that can eat away at metals over the winter. So ditch the old oil now. To change the oil, run the engine for a few minutes to warm up the oil. If the boat has been hauled, you’ll need the proper motor flushers for the engines (or plumb the intake pumps) to supply cooling water from a garden hose. Installing a Groco SSC engine flush kit ($96.77, jamestowndistributors.com) makes this job easy. Then shut down and drain or pump out the old oil. Change the oil filter and fill the crankcase with fresh oil (per the manufacturer’s specifications). Also change the oil for the transmissions at this time.
3. Good Drainage
Open all drain plugs to purge the raw-water cooling systems. Plug locations vary by manufacturer, so check your manuals. Use a stiff wire to clear any sediment from drains. Also, bump the ignition to turn over each engine (without starting it) to clear water from the pumps. If your boat stays afloat all winter, you can drain the systems by first closing the seacocks for the raw-water inlets, then removing the inlet hoses and intake-pump covers, as well as all drain plugs. After clearing the raw-water systems, replace all of the drain plugs. If you removed the intake-pump covers, give each impeller a light coat of Vaseline and replace the covers.