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What To Do If Your Vessel Strikes A Submerged Object

Striking submerged object claims are the second most frequent type that BoatUS Marine Insurance sees. If you can't avoid it, know what do if you hit something in the water.

Log floating in lake


In my three decades as an accredited marine surveyor, I've seen struck submerged object (SSO) claims that involve floating logs, pilings, dock timbers, tree branches, moorings, dredge pipes, floating nets, crab traps with lines and buoys, sunken cars, refrigerators, shopping carts. ... I can go on and on. If it's in the water, someone has hit it.

By the nature of their designs or usage, some vessels are prone to striking submerged objects more than others — particularly those with deeper drafts or planing boats capable of higher speeds. Beyond the boat, vessels that operate in shallow bodies of water or in busy ports where there is a lot of commercial construction, or those around tidal shorelines or river mouths with fallen trees or branches or other debris, have a much great chance of striking a submerged object.

For most boaters, the question is not if they will strike a submerged object, but when, which explains why one question I'm routinely asked: "What should I do if my vessel strikes a submerged object?"

The well-being and safety of you and your passengers is priority number one, while taking action to mitigate further damage to your vessel is priority number two. Then I offer the following game plan:

1. First, when you realize that you may have struck a submerged object, bring the vessel to dead slow or stop.

2. If you're in danger — assume that you are — have everyone on board put on a life jacket if they haven't already.

3. You or a crewmember should immediately check all of the bilges to confirm that the vessel is not taking on water. If it is, do what you can to slow or stop the water flow. Stuff the hole with a rag, bedding, or whatever you have on board until help arrives.

4. Determine that you're not aground. If the engines have stalled, try to restart them. If they start, try shifting forward and reverse to confirm you haven't lost propulsion. If you're in an area where the boat is drifting and may drift up on a sandbar or into a bridge, dock, or other vessel, anchor your vessel if possible.

Tire debris in the ocean

SSO claims run the gamut from floating debris to fishing nets to trash, like this discarded tire. (Photo: publishing)

5. Stay aware of your surroundings. I've seen cases where a vessel experiences a casualty, such as striking a submerged object, then experiences a second casualty because the vessel drifts into something else because the captain took his or her attention from the helm.

6. If the engine, transmission, and bilge seem OK, slowly accelerate the vessel and pay close attention for any evidence of noise or vibration. Watch your engine gauges closely to make sure that all systems are functioning normally. Putting the engine in gear or even starting it may cause increased water pressure or vibration, which may turn a nonleak into a leak. Inspect bilges carefully at this point.

7. Following such an event, bring the boat to your marina and ask them to check it over and confirm there's no damage. In some cases, this may require a diver to check under your vessel, or the marina may haul your vessel to inspect the hull, bottom, and running gear. Some insurance policies, such as those from BoatUS, will pay to have your boat short-hauled if there's a possibility of damage that could put the boat in further peril.

Avoiding SSOs

Striking something in the water can be expensive and time-consuming to fix. Sometimes the object may be floating on the surface or bobbing up and down or, worse, just below the surface. Usually, a careful lookout will help you detect and avoid a collision. Be extra alert when you're in an area known for mooring fields or fish traps. Be especially vigilant after storms or extreme high tides have occurred as canvas, shrinkwrap covers, or debris may have blown into the water, or extreme high tides may have caused trees, wood pilings, or debris to float from the shoreline into the water.

Avoiding junk in the water and on the bottom is part good seamanship and part luck. If you're unfortunate enough to strike a submerged object, hopefully you'll be prepared, will understand what has occurred, and will take swift and prudent action to ensure the safety of your crew and vessel.

SSOs: Damage By Design

Regardless of the SSO threat being universal, the type of vessel, and the propulsion system that drives it, largely dictates the extent — and location — of where the damage is done.

Take a look to see if your boat fits one of these categories:

Sailing Vessel:

When a sailing vessel strikes a submerged object, the damage is almost always at the lower leading edge of the keel, but usually the impact is at less than 8 knots. Typically, a forward-moving impact may result in the front of the keel pulling downward causing a fracture or separation at the forward end of the hull/keel joint and the aft end of the keel is pushed upward. A severe impact may also cause damage to the internal stringers, floors, and bulkheads, or their tabbing, and could damage the rig, including the standing rigging, mast step, and chain plates.

Look for leaks in the bilge where the keel attaches. Check throughout the boat to determine where the impact occurred, and inspect for damage. Unless the boat is taking on water fast, you can probably get back home slowly, though you may have to motor if the rig is damaged or weakened. Once home, you'll want to have it immediately inspected.

Outboard-Powered Vessel:

When a vessel with outboard motors strikes a submerged object, it's usually going pretty fast, which results in bent propellers, propeller shafts, and possibly damage to the lower gear housing The outboard may kick up following a severe impact, which may result in damage to the trim and tilt system.

In the event of a severe impact to the outboards, there may be damage to the transom. If a line or a crab trap gets wrapped up in your prop, this may cause torsional damage to your drive system, which may result in a bent prop, spun hub on your propeller, chipped or damaged gears, or a bent, sheared or twisted prop shaft or vertical drive shaft. If the vertical shaft shears off, the engine will lose propulsion and will overheat if not shut down because the vertical shaft rotates the water pump impeller, located on the lower unit.

If you strike something in the water, the leading edge of your outboard leg and/or your prop may be damaged, so proceed slowly, especially if you feel a vibration. Because it's easy to tilt up an outboard, it's easy to inspect.

If only the prop is damaged and you have a spare, you may be able to replace it and get on your way. If you have twin engines, you may be lucky and only one is damaged, so you can get home on the other.

Inboard-Powered Vessel:

When a vessel with inboard power strikes a submerged object, it often results in bent running gears, such as props, shafts, struts, and rudders. A severe impact may tear out a prop shaft, strut, or rudder or may drive a strut through the hull bottom. This will result in the vessel taking on water. The vessel may jolt or come to an abrupt stop or may pitch forward, which may result in seawater rushing forward up the engine's exhaust.

In rare cases, the water can enter the cylinders through the exhaust valves, and because water does not compress, you may end up with a condition known as hydrolock. This could bend or break a connecting rod resulting in a catastrophic engine failure.

If you pick up a line in your props or shafts, you will experience a vibration. Again, if you have twin engines and the line is just wrapped around one prop, you can get back home on the other engine though, depending on conditions, you may be able to dive and cut away the offending line. If a line gets wrapped around both props or shafts, when in gear, it can wind up on both shafts and winch both shafts together, bending them and possibly damaging the struts, which again can cause the boat to take on water.

Impact can also cause damage to your transmission's clutches and your drive plate. You may find that you have no forward or reverse and you'll need a tow.

Sterndrive (I/O) Powered Vessel:

When a vessel with a sterndrive strikes a submerged object, it often results in bent propellers, propeller shafts and possibly damage to the upper drive housing or lower gear housing. The outdrive could even be torn from the transom assembly.

When this happens, the vessel will lose propulsion and water will start to flood the vessel through the gimbal bearing, which is where the drive shaft for the outdrive penetrates the transom of the vessel. The gimbal bearing can be plugged with a rag or other available object to slow the water flow. The vessel will have to be hauled immediately. Lines or crab pots entangled in the prop may result in torsional damage to the outdrive such as a bent prop, bent or twisted prop shaft, twisted or broken vertical shaft and broken or stripped gears, broken U-joints, spun propeller hub or engine coupler, or stripped splines on the engine coupler or drive yoke shaft.

If it looks like it's just a bent prop, you may be able to get back home if you go slowly — too fast and vibration can cause further damage.

Pod Drives:

Some newer vessels are equipped with pod drives such as the Volvo Penta IPS drive or Mercruiser Zeus drive. These are like a hybrid between a sterndrive and an inboard and are fitted with larger inboard diesel engines. Pod drives will suffer similar impact damage or torsional damage as described for a sterndrive or inboard. The parts are just larger and more expensive. They can also suffer electronic damage to the computer controlled steering, shift mechanisms, electronic steering controls or electronic shift and throttle controls.

A unique aspect of the pod drives is that they are designed to break away from the vessel in the event of a high speed impact, and if all works as designed, the vessel should not take on any water. Because pod drives are positioned farther forward than sterndrives, you probably won't be able to make any temporary repairs.

My Firsthand Experience With SSOs

Years ago, as I was motoring my 45-foot sailboat 120 miles from the Washington, D.C., area to a new marina on the Chesapeake Bay, I struck a floating log in the Potomac River. I was at the wheel by myself. I once hit a log off Vancouver Island, British Columbia, and only saw it moments before impact. That log did no more damage than the diesel-engine sized ice chunk that I struck in Alaska, but the log in the Potomac hit just right and damaged my feathering Max-Prop, the prop shaft, and the shaft log, to which the stuffing box was attached.

Right after I hit it, I experienced what can only be described as an "expensive noise" — a rapid wobble-wobble-thunk-thunk that made me quickly throw the engine into neutral. After throttling back, I dove into the bilge, expecting to find mangled machinery and a fire hose of water gushing in, but there was no smoking steel or leaking water. Turning the shaft by hand was almost impossible, though, and I knew something was really wrong. SSO incidents are never fun.

I found myself miles from either marina, in the widest, most desolate part of the Potomac — without a BoatUS towing membership (which, I should note, I quickly remedied on my return). Fortunately, I found that at idle speed, the noise and vibration were not too bad, though I kept checking for leaks every half-hour. Because the stuffing box was a bit wobbly now, there was certainly a lot more water in the bilge than usual, but the pump was easily keeping up. The wind was light and on the nose, though it soon changed as a front was sweeping through, and I was able to sail the rest of the way, eventually limping through the fog at idle speed to my new marina.

The boat was hauled the next day. The mechanic showed me the damage. I was back on the water quickly but with a keener eye for floating junk. Had I been more observant, I'd have realized that the river water was muddy-looking because there had just been heavy rainstorms along the Potomac. Those storms washed all kinds of debris into the water and most likely dislodged the partially submerged tree I hit.

Now, not only do I keep a sharper lookout for debris in the water, but I also consider whether there have been exceptionally high tides or heavy rains recently. And I keep my BoatUS towing membership current.

— Charles Fort

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Ron Alcus

Contributor, BoatUS Magazine

Ron Alcus has been a marine surveyor for more than 30 years and has seen pretty much every type of SSO claim you can think of.