In every manual, flushing engines (inboard or outboard) with freshwater is recommended after use. You understand why — the effects of salt and corrosion are likely large contributing factors to our employment. Salt left to corrode in the engine remains mostly unseen, and its consequent wear and tear will show up as poor performance and shorter engine life and failure, effects that will only show after some months, so it’s useful to remind green deckhands of this.
A flush should occur after every use, but if you know you’re just moving anchorages and are putting that tender back in the water in six hours, you could probably forgo it until after, especially if you’ve got other stuff on the go and beach setups to prepare. Just make a note — plans always change.
We’ll cover jets and outboards; however, let’s go over some pointers for both. If you’re in an enclosed tender bay, consider proper ventilation as you’re running your engines. You wouldn’t hang out in the garage with a running car, so don’t do the same with the tender. If the seas allow it, keep the shell door open until you’ve flushed, and use any other means of ventilation available, e.g., extractor fans, mechanical blows, etc. On a guest-related note, if your tenders are housed on deck, it’s going to be noisy having them run as you flush, so try not to do it in the middle of dinner service.
For older outboards, attach a pair of what appear to be earmuffs to the water intake at the bottom of the outboard. This connects to a hose; turn it on, and then start the engine. For outboards, do not engage the engine/put it in gear unless explicitly stated in the manual. Let it run for more than one minute, but no longer than five. There should be a clear, steady telltale stream. Then turn off the engine and shut off the water. For newer outboards, there will be a direct flushing point connection, and some may not even require the engine to be run. Check the manual.
Inboard motors are not much different — the flushing connection point is usually under the driver’s seat or on the transom. Again, turn on the hose and start the engine for the same amount of time, and, unlike outboards, it may (depending on the make) be necessary to apply a very slight throttle. Once completed, shut off the water and kill the engine.
For both inboard and outboard, check the hose pressure. It should be the same pressure you’d expect from a household garden hose. I’ve seen deck outlets with significantly more pressure than that, so partially open the outlet until you get the right pressure. Too much pressure can cause damage to impellers and pumps and too little may overheat the engine.
This article was orginally published in the May 2023 issue of Dockwalk.