Stern drive in saltwater

[Privilege]

For many years I had heard that out-drives in saltwater were not a good idea. However on most modern catamarans, saildrives are becoming the norm and they are just the same as out-drives. Like any soft metal left in saltwater, they require special attention as they are more prone to corrosion. A good tip that I once heard and which seems to make sense is to always leave the drive down when not in use. This leaves the bellows compressed and stops barnacles from forming within the folds. If left up and barnacles settle, they can damage the rubber when compressed.

[LLizzard]

Originally Posted by Privilege

For many years I had heard that out-drives in saltwater were not a good idea. However on most modern catamarans, saildrives are becoming the norm and they are just the same as out-drives. Like any soft metal left in saltwater, they require special attention as they are more prone to corrosion. A good tip that I once heard and which seems to make sense is to always leave the drive down when not in use. This leaves the bellows compressed and stops barnacles from forming within the folds. If left up and barnacles settle, they can damage the rubber when compressed.

Also when the drive is down, the lifting rams are not as exposed to growth. If the drive is up somewhat, tube worms or other hard growth can attach to them. When the drive is then put al the way down, that growth can cut the seals inside the ram.
There are simply places you cannot access to clean the growth from. Mechanically and from a metallurgy standpoint, it's not a sound way to store your boat. However, there are probably more outdrive boats than shaft drive, so it can be done with proper care and maintenance.
In areas where they are hauled for the winter, it's a bit better because you have months to clean, inspect, and replace what's needed.
In year around boating areas, that usually doe not happen as regularly.
One thing to consider is resale value on an in the water IO boat can be lower, because many people simply will not consider them.
I've had both, but prefer shaft drive.

[Colin A]

Originally Posted by jsc7

I have read some forum posts (on other web sites) that state having a stern drive moored in a slip in salt water is a "fool's errand" because corrosion is constant and problematic. Moreover, if the bellows lose their integrity then the boat can sink.

How accurate is that?

Bellows do sink boats. Quite a bit actually. Mostly it's due to lack of maintenance.
In general the drives should be pulled off every year fluid changes and everything inspected. TO be safe water pumps and bellows get changed every 2 years. Many people go 3 years on water pumps and 5 years on bellows but it dosen't always work out.

Corrosion varies certain drives used to have more problems then they do now. If your buying used make sure everything has been done maintenance wise.

[Cheechako]

Originally Posted by Colin A

Bellows do sink boats. Quite a bit actually. Mostly it's due to lack of maintenance.
In general the drives should be pulled off every year fluid changes and everything inspected. TO be safe water pumps and bellows get changed every 2 years. Many people go 3 years on water pumps and 5 years on bellows but it dosen't always work out.

Corrosion varies certain drives used to have more problems then they do now. If your buying used make sure everything has been done maintenance wise.

Let's mix in a little reality:
(Boats That Sank While Underway)
Waves Over The Gunwales 30%
Leaks At Through-hulls/Hoses 18%
No drain plug 12%
Leaks At Raw Water Cooling Systems/Exhaust 12%
Navigational Error (Grounding) 10%
Boat Construction (Structural Failure) 6%
Leaks At Outdrive Boots 4%
Struck Submerged Object 4%
Other 4%

( Boats That Sank At The Dock)
Failure Of Through-hull Fittings Below The Waterline 50%
Rain and Snow (All Involved Self- bailing cockpits!) 32%
Failure of Through-hull Fittings Above The Waterline 9%
Improper Mooring Arrangements 8% (Loss to Hurricanes Not Included)
Other 4%

Looks like if you are really thinking of changing your boot every 2 years you better change your seacocks every few months!

[Colin A]

Originally Posted by Cheechako

Let's mix in a little reality:
(Boats That Sank While Underway)
Waves Over The Gunwales 30%
Leaks At Through-hulls/Hoses 18%
No drain plug 12%
Leaks At Raw Water Cooling Systems/Exhaust 12%
Navigational Error (Grounding) 10%
Boat Construction (Structural Failure) 6%
Leaks At Outdrive Boots 4%
Struck Submerged Object 4%
Other 4%

( Boats That Sank At The Dock)
Failure Of Through-hull Fittings Below The Waterline 50%
Rain and Snow (All Involved Self- bailing cockpits!) 32%
Failure of Through-hull Fittings Above The Waterline 9%
Improper Mooring Arrangements 8% (Loss to Hurricanes Not Included)
Other 4%

Looks like if you are really thinking of changing your boot every 2 years you better change your seacocks every few months!

Right but seacocks often failed when they were 15 years old not 5. Volvo actually lists a 2 year cycle replacement on the bellows mercruiser just says inspect and replace as needed last I knew.

I used to work claims for a boat/yacht insurance company. On claims thru the unit I worked in, regarding sinkings, about 65-70% were sinkings at the dock mostly from heavy rain and poor drainage or scupper issues. I would say about 15% of sinkings at dock were related to sterndrive bellows shift boots etc. It was pretty much a weekly thing.
I actually sank a sterndrive boat once. U joint gave out took out the bellows and down we went. That's not to say there aren't plenty of ways to sink a boat besides a stern drive there are, but bellows deserve special attention just like stuffing boxes etc. The only boat I had sink on me while I was onboard from a lifetime working on boats for a living was a sterndrive. Which I will admit might make me slightly biased.

This infographic from Boat US lines up pretty well with what I saw for claims.
http://ww1.prweb.com/prfiles/2014/06...%206_30_14.pdf

[flyingfin]

Here is a good article by David Pascoe for those who want to consider leaving outdrives in a slip instead of on a rack or trailer

Maintenance and Troubleshooting : Maintaining Stern Drives