Recreational Boating Safety – Engine TLC

Bob CurrieBy Bob Currie, Recreational Boating Safety Specialist
U. S. Coast Guard Auxiliary Base Galveston Flotilla
Boat owners like to joke that the word “boat” is an acronym for “break out another thousand.” The best way for this to turn into a self-fulfilling prophecy is to fail to take care of your engine during maintenance, operation, and storage.
Trip Maintenance and Checks
Trip maintenance is what you do to protect your engine before and after a trip. Boats are quite different from automobiles in this regard. Most people when they want to take a trip in their car just climb in, crank the engine, and head to their destination. If anything happens along the way they can call for a tow and not be out a considerable sum. The boat owner, however, is in a different fix if something goes wrong once they leave the dock. For that reason, it pays to check a few things before you take off, and while the automobile driver merely parks the vehicle and exits without a second thought, the prudent boat owner has a set of tasks to perform so that the boat will be ready to go on the next trip.

The Base Galveston Flotilla of the US Coast Guard Auxiliary operates out of the US Coast Guard base on Galveston Island. They aid the Coast Guard by providing maritime observation patrols in Galveston Bay; by providing recreational boating vessel safety checks; and by working alongside Coast Guard members in maritime accident investigation, small boat training, providing a safety zone, Aids to Navigation verification, cooking in base and station galleys and aboard cutters; and on the Coast Guard Drone Team.

Pre-Trip Check
The time to find out if you have any engine concerns is before you are at the ramp trying to get the engine started. The best time to perform a pre-trip engine check is the night before. Day of trip inspections tend to not be as thorough as most boat operators are anxious to get out there on the water. The longer the time between trips the more thorough should the pre-trip inspection be. Make your own checklist and follow it. You can laminate your checklist so that it lasts longer. Here are some recommendations for your list. Keep in mind that the pre-trip inspection for boats with outboard motors will be different from the checklist for an inboard motor.

  1. Test the steering (don’t forget to remove any motor support first)
  2. Test the tilt/trim, and look for any hydraulic leaks
  3. Check the bilge for water and test the bilge pump
  4. Connect the fuel line, turn the ignition on to pressurize, and check for fuel leaks
  5. Check engine fluids (oil, transmission oil, coolant if inboard with coolant system)
  6. Check hoses and clamps
  7. Check battery and switch connections for tightness and no corrosion
  8. Check sacrificial anodes for excessive loss of material (greater than half)
  9. Check rudder anode for tightness and excessive loss of material
  10. Check prop nut for tightness and presence of cotter pin
  11. Check prop for large nicks that could cause engine imbalance
  12. Check prop to make sure a blade isn’t bent or cracked
  13. Check water intakes for blockage from debris or mud dauber nests
  14. Check water flow tube for debris and mud dauber nests
  15. Check your exhaust for debris and mud dauber nests
  16. Check fuel amount, and perform a smell test if possible (bad gas smells sour)

Engine Operation
I am sure there are some people reading this who think I am about to say don’t run your boat at wide-open throttle (WOT), but that is not the case. Unlike your personal auto which is not designed to be operated at WOT except for acceleration, boat engines are designed to be run at WOT for extended periods. The big caveat with doing so is your fuel consumption will double at WOT over a three quarter throttle cruising speed. Unlike your automobile, a boat engine is designed for quick starts using WOT in order to get on plane quickly and efficiently. You stress your engine unnecessarily by making slow starts using a slow advancement of the throttle. One of the best articles I have seen on boat engine operation can be found at . I have discussed those engine-killing no-nos below.

Engine Killer Number One: Dry Starts
Whether on purpose or whether done accidentally, dry starts, that is, cranking an engine without the water intake being submerged, are very detrimental to your engine. Water is not only used for coolant, but also for lubrication, and a dry start will destroy your water impeller. Accidental dry starts occur when the boat operator bumps the engine to test the battery. You should keep your batteries fully charged during your boat’s time out of the water. It is imperative that you use a marine trickle charger that is designed to shut off when the battery is fully charged so that an overcharge doesn’t occur. Such chargers have indicator lights that let you know the condition of your battery system.

Engine Killer Number Two: Excessive Warming Up
The modern fuel injected outboard or inboard engine does not need much warmup. The time it takes to cast off your mooring lines and move away from the dock is enough time to warm the modern fuel injected engine so that you can accelerate and get up on plane.

Engine Killer Number Three: Slow Shifting
You can hear the nerve-racking grinding sound from a mile away as an inexperienced boater slowly shifts into gear, mistakenly trying to avoid the big clunk that occurs from shifting quickly. That grinding sound is the clutch wearing out. With the newer engines, that old rule of waiting five seconds to shift from forward to neutral to reverse is no longer necessary. A second or so is all that is needed.

Engine Killer Number Four: Slow Planing
The idea is to reach plane quickly. According to Boating World, “Easing a boat on plane is far worse for an engine that jamming the throttle quickly.” Acceleration is when an engine is at its greatest stress, so the idea is to minimize that amount of time. Planing boats are under a great stress when they are not quite on plane but are instead operating as a displacement hull. The point at which you go from displacement hull to planing hull changes with load, but you should have an idea at what speed your boat makes that transition, and that speed should be avoided to reduce engine stress.

Engine Killer Number Five: Improper Trim
I operate a great deal in the Intracoastal Waterway, which is a fairly straight channel. I can spot an improperly trimmed boat a mile away. A boat that is trimmed down too far creates a much larger wake than one trimmed properly, and a boat that is trimmed too high will bounce up and down as the hull breaches too much. We call this bouncing up and down “porpoising.” This is an ironic misnomer, as the marine mammal the up and down action mimics is the dolphin. There are no porpoises in the Gulf of Mexico. As dolphins move through the water, they break the surface for less than a second to breathe in through their blow holes. Similarly, a boat that is trimmed too high will raise its hull up briefly and then fall back down into the water, almost to a pre-plane depth. As the boat falls back down into the water, it displaces much more water and puts a strain on the engine. You don’t have to see a boat to know that it is porpoising; you can hear the engine as it is overloaded during the down cycle (aruh…aruh…aruh…). When starting from a standstill, the engine trim should be all the way down. As you come up on plane, increase the trim. Once on plane, increase the trim further until more of the hull breaks free. There will be a sudden increase in speed as optimal trim is reached. If you trim up too high, the boat will start to porpoise. At that point lower the trim slightly and you will be running at the most efficient trim. If you encounter a section of rough water, reduce speed and slightly lower the trim to keep the boat from porpoising.

Engine Killer Number Six: Suboptimal Speeds
What?! You mean you can go too slow in a boat? Yes you can, if your consideration is efficiency as well as engine life. There is a speed at which your engine is operating at its best efficiency, known as its cruising speed. The old rule of thumb is you can find your cruising speed somewhere between two thirds and three fourths throttle. At this speed the engine runs quieter as long as the trim is properly adjusted for the speed and water conditions. The idea is to get as much of the hull out of the water as possible yet not so far that the boat begins to porpoise. When more of the hull is in the water, the engine has to work harder to maintain a certain speed. Cruising speed is not always the same; wind and water conditions can cause the optimum speed to be lower or even faster with a good tail wind.

Engine Killer Number Seven: Aggressive Driving in Rough Water
You’ve seen those big sport fisher boats headed out to the banks. They plow right through the rough seas, occasionally coming completely out of the water. The operator would tell you his boat is made for this stuff. That well may be true for the hull (but I doubt it), but it sure isn’t true for the engine or engines. When the propellers clear the water, the engine will over-rev briefly (never a good thing) and then when the props, now running too fast, re-enter the water they are subjected to large forces which suddenly bring the engine under a load higher than for which it was designed. Here is an analogy for you: the weed eater. Under normal function the weed eater will easily cut moderate height weeds, but run it into a large, thick clump of weeds and the engine speed will drop quickly from 10,000 rpm to almost stopped, greatly stressing the engine. That is what happens when a marine engine prop suddenly drops back down into the water after running full speed in the air. The sounds are similar. The engine stresses are the same.

Post-Trip and Storage TLC
The most important thing you can do after a trip on the water is to flush the engine with fresh water according to the manufacturer’s instructions. Be sure to refill the fuel tank and add stabilizers as instructed by your engine manual. Then follow the majority of the pre-trip list items to make sure nothing has worked lose, started leaking, or taken up debris. Other than these recommendations, it is important to follow the manufacturer’s preventive maintenance schedule.

Your engine in many cases costs more than your boat. It is only logical that you should provide it with tender loving care so that you get the most from your investment. The owner’s manual provided by the manufacturer is the best source for maintenance guidelines, but the recommendations here will help your engine live a long and healthy life.

For more information on boating safety, please visit the Official Website of the U.S. Coast Guard’s Boating Safety Division at Questions about the US Coast Guard Auxiliary or our free Vessel Safety Check program may be directed to me at [email protected] I am available to perform free Vessel Safety Checks, and I will come to your location to perform them. SAFE BOATING!


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