Flushing an engine or the A/C system used to mean disconnecting the inlet hose from the raw water strainer and attaching a longer hose from the strainer to a bucket for flushing and inserting the antifreeze solution. Here is a method that eliminated removing ANY hoses and can be used for any engine or the A/C water system.

I use Groco raw water strainers for my auxiliary and my generator, as well as my A/C water input. These strainers have a screw on cap. At a plumbing supply I purchased a 2”x¾” and a 2½”x¾” bushing for my two different-sized Groco strainers and two garden hose adapters to ¾” pipe. I screwed the hose adapter into each bushing to make a flushing cap. The cap installed on the filter is pictured here.

Groco Raw Water Strainer with Flushing Cap

The first step is to shut the seacock and remove the strainer basket for cleaning. Without the basket in place, screw on the flushing cap and connect a hose to a 5-gallon bucket of fresh water. I run the engine or A/C system about 10 minutes to completely flush all traces of salt from the system. Keep the bucket filled as the engine sucks the fresh water out of the bucket.

Fresh Water Flush thru Engine

After a fresh water flush, mix 4 gallons of a 50/50 solution of the propylene glycol (environment-friendlier) antifreeze. To the end of the hose in the previous step, connect a drill-powered pump and another short hose. Start the drill pump and open the seacock. Antifreeze will fill the strainer and then go out the seacock. It will not get past the rubber impeller of the positive-displacement raw water pump into the engine, but will go out the seacock instead. Pump about ¾ of a gallon or until you feel the hose to the seacock is full. Then shut the seacock before stopping the drill pump. This ensures that no seawater will enter the seacock and dilute the antifreeze.

Now simply start the engine and let it suck the antifreeze thru it and run until the dark color of the antifreeze is seen at the exhaust discharge. Shut down the engine and remove the flushing cap and replace the strainer basket and the original cap of the Groco strainer.

Advantages are a faster flush without having to remove/replace clamps and hoses. Also there is no need to suck the water out of the seacock hoses with a syringe and refill with antifreeze, thus saving more time and aggravation.

Pump Antifreeze thru Seacock