Boatbull: myths, urban legends and downright nonsense, outdrives in salt water

A look at some of the bull that circulates about boats, various forums, internet groups & chats are full of very good information but, equally there is really poor advice and, some common misconceptions, driven by a lot of people who are grossly misinformed and will still die on their hill with their opinions, today, lets look at outdrives in salt water.

The outdrive as we know it has been around since the late 1950s or early 1960s, Volvo Penta, Mercruiser and OMC being the major players, BMW also produced an outdrive and so did Yamaha, Yanmar also makes their own drive. It was genius, a steerable unit which could be coupled to marinized automotive engines in various sizes for everything for runabouts to race boats.

So, if these units have been around for over sixty years and are still going strong, so why the lack of love for outdrives in salt water? To be more specific, why the common, "never buy a outdrive motor used in saltwater"?

Business and salt water

About 97 percent of the worlds water is salt (Wikipedia), think on that for a second. Purely from a business model it would not make much sense to make a boating product to only be used in fresh water, most of which is located in Canada, the Great Lakes and Russia, hardly the most sun drenched of spots for a lot of the year, so even less sense to produce a product that has limited usage time also.

"But my friend told me"

This one happens a lot, somebody who is uninformed or biased has spread this vicious rumor, the "friend" can also be a poster on a forum or group chat.

Where a lot of this stems from is when somebody has a bad experience, they bought a boat with a poorly maintained motor that just happened to have an outdrive attached to it. The same goes for any marine engine, some are more tolerant of a bit of neglect, but in the end, they all need maintenance.

Modern outdrives

One of the newer Volvo Penta outdrive designs, this one includes an oil filter for the drive oil, an oil level and quality sensor plus a sensor to tell you if water is in the bellows, this is as advanced as it gets.

Mercruiser Bravo 4 forward facing drive, you don't see them very often, they are designed for use on ski boats, replacing a single central shaft. 

Today Volvo Penta and Mercruiser are the mainstay of outdrive suppliers, they can be coupled to either diesel or gas motors, from very timid right up to supercharged hugely powerful motors than can run on race fuel, these are obviously more specialized.

There is also Konrad, another supplier of outdrives, at one point they were heavily involved with commercial boats and I believe military also.

So, if you want to leave you outdrive powered boat in the water for a long time (what a strange concept, I know!), will it still be there when you come back or will the ravages of the sea have turned it into a colander?

Corrosion resistance

Saltwater is highly corrosive, fresh water is too, water is called the universal solvent due to its ability to dissolve more substances than any other liquid. Fortunately there are various systems in place that slow corrosion down on outdrives;

Coatings, not just any sort of paint either, I imagine a hot baked powder coating or similar, whatever it is, it does not come off easily, forming an extremely hard and resistant bond to the underlying metal.

Composites, plastics (bit more scientific than that), but basically non metallic components made of highly resistant materials with amazing mechanical strength with the added benefit of not corroding or breaking down in seawater.

Anti corrosion systems, both Volvo Penta and Mercruiser have electronic anti corrosion systems, very simple and very clever, basically all outdrives and boats have sacrificial pieces of metal attached to them called anodes, these anodes are more reactive (called less noble) to seawater than the materials of the outdrive, the electronic systems ensure that the drive remains more cathodic and so the anodes do their job.

Antifoulings, specifically aimed at keeping the propellers clean, a major player here is Propspeed, I can attest to its effectiveness. In my part of the world in Southern Spain, its considered a high fouling area, one year to the next Propspeed kept growth at bay, quite literally the props came out the same way they looked after painting a year previously.

Benefits of outdrives

This does not seem to be argued enough, there are many cases made for outboards, but rarely for outdrives, three reasons to have outdrives;

Dealer network, there are a lot of mechanics who can work on outdrives, especially ones that do not require super specialist diagnostic software.

Swim platform, you retain the platform, this is much more difficult and expensive to do with outboards.

Entanglement, it is not too difficult to untangle ropes from outdrives, contrary to what you might imagine, I usually end up doing a few every year, so far I have not had to get into the water to do it, maybe some boats with extreme sized bathing platforms where you simply cannot reach would be an issue.

Summary

I would imagine outdrives have powered more types of boats for more years than any other propulsion system, it is true that outboards in a lot of markets have taken over the outdrive, but simply put they are not for everyone and every boat type. The bull about never buying or using an outdrive that's touched saltwater is simply just that, bull. I am sure a lot of the same people who steadfastly believe this myth would have a fit if they saw the literally thousands of boats in the Mediterranean, which is a very salty body of water filled with outdrive powered boats that only get flushed (if at all) when the boat comes out for annual service.

Something I haven't really touched on is the engines these drives are coupled too. The benefit of outdrives is they are not limited, they can be mated to small and large (and very powerful) diesel motors, four and six cylinders from Volvo, V8s from Yanmar, I have even seen a Cummins B series motor mated to a Konrad drive, then, we have the gas motors from Mercruiser, V6 & V8 from runabouts to offshore racing, incidentally Mercruiser have sold their drives to use with varying makes of diesel engines, Yanmar, Nanni, VM Motori to name a few, so there is something for every boat and use, mark my words, the outdrive is here to stay and, don't believe the bull.

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