Brackish water and flushing an outboard

Fresh water is 8.33 pounds per gallon. Salt water is 9.0 pounds per gallon. Weigh a gallon of your water and you'll have your answer.

Drain the OB engine completely, then store it in any position the mfr recommends. You just need to ensure you don't have water in the lower unit and other orifices during freezing temps. If you feel the need to flush, do it once a month or whatever feels right at your convenience.

Engines are more tolerant of saltwater than I think we give them credit for. I have NEVER flushed my diesels and they're 3000+ hrs/38 yrs old and still going strong.

I've always thought you were better off tipping up the motor. Assumed saltwater corrosion was long term bad and that marine growth would start to form on the immersed parts. From Psneeld's chart, it appears that the OP is essentially in fresh water. Guess I'd just leave it up or down as you prefer and not worry about flushing it.

Ted

To flush or not to flush , is not the question.

Weather you tilt the engine out of the water after use may have a larger effect on service life.

Please check my Science... Doesn't marine growth require light? I know fauna (weeds & grasses) don't grow in darkness. What about barnacles and such? Just wondering...


Oh, and Merry Christmas to all. I hope Santa was as good to all as he was to this this transplanted Texan.

The parts in most lower units are like a British battery.

aluminum, steel ,SS, brass , bronze and God knows what else.

In addition to the electric corrosion having shaft seals underwater 100% of the time is an invitation to failure.

When sea water gets inside the lower unit the real fun begins.

FF said:

The parts in most lower units are like a British battery.

aluminum, steel ,SS, brass , bronze and God knows what else.

In addition to the electric corrosion having shaft seals underwater 100% of the time is an invitation to failure.

When sea water gets inside the lower unit the real fun begins.

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I respect your opinions and doing it whatever way works for you. I do however feel your views are skewed a bit by years of history and not as much in touch with today's technology on outboards. Around us, almost all are kept in water. On the lake, it was the same. When I was a kid they use to joke about a Mercury mechanic's most important tool being a pry bar to force the lower unit apart. The dealers would warn customers in advance that they might have to replace the housing after it broke in the process. The minerals in our water practically welded it together.

But other motors started doing a better job and soon all followed. Now, we don't ignore the units. We clean and maintain just as we do the hull. And lower unit maintenance, always replacing crush washers (or drain plug gaskets). That's the key.

mbevins said:

Being close to the freeway were about 13 miles up from the coast.
Which is about 5 miles down river from the power plant. You'd think that would be far enough up to be fresh but we still get tidal action so I assume we get salt with it.
I like the chart in post 4.
225hp outboard motors get expensive when you replace them for no reason.

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Rivers may well be tidal well upstream of the intrusion of the saltwater wedge. The dynamic effect of tides on water height of the Fraser River and indeed fish migration occurs above Mission, BC (60 nm upstream of the mouth) even at the end of August during years of low river flow. However, the salt water wedge only reaches Annacis Island, ~18 nm upstream and then only in the periods of lowest river flows and highest tides. Al Ages' classic paper shows that the saltwater wedge in the Fraser River is clearly quite dynamic with river flows and tidal heights:

http://www.dfo-mpo.gc.ca/Library/54922.pdf

Figure 9 shows that the wedge doesn't get anywhere near where our vessel is tied up (just above Gary Point). In December parts of the hull of our vessel will be in saltwater. (Figures 46+). At sometimes of the year, the halocline is visible on the echosounder. At other times of the year, it isn't visible which means either the halocline is above the transducer, or alternatively the saltwater wedge isn't present.

The only way to be certain is to use a salinity meter at depth across a tidal time series.

Merry Christmas!

Jim

"When I was a kid they use to joke about a Mercury mechanic's most important tool being a pry bar to force the lower unit apart."

Some things never change. Even today a Harley mechanics best too is a bigger hammer!

Unused outboards do last a long time on a lake , but wrap a fish line in the prop in fresh or sea water or simply have a barnacle start growing in the seal , and better factory paint is not much help.

Aluminum anti seize is what i use.


Just be cautious about torque specs as most are for dry threads.

Outboard vs. Inboard Flushing

Why flush an outboard when you don't flush a diesel engine? Because diesel engines, and many inboard gas engines, are fresh water cooled. The only parts that come in contact with seawater are the raw water pump, heat exchanger(s) and exhaust elbow, and those parts are typically made from galvanically noble, corrosion resistant materials, copper, copper-nickel, bronze, stainless steel, and they are replaceable. Outboards, on the other hand, are entirely raw water cooled and the powerheads (which are technically replaceable, albeit at great expense) are aluminum, a highly corrosion prone, galvanically ignoble metal. So while uncommon, flushing an outboard wouldn't hurt. For daily use it's probably less necessary. If, on the other hand, it was to remain unused for weeks or months, flushing would make more sense.

Steve DAntonio said:

If, on the other hand, it was to remain unused for weeks or months, flushing would make more sense.

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Well, that's a problem we don't have.