Recreational Boating Safety – Operating a Twin Engine Boat on One Engine

By Bob Currie, Vessel Examiner
United States Coast Guard Auxiliary Flotilla 081-06-08
For those who venture far from shore in their search for boating recreation, be that simply cruising or deep sea fishing, the twin engine option is more popular than the single engine option. Maneuvering a boat with twin engines is, however, not just a little different from maneuvering a single engine boat; rather, it requires a much higher skill level. Maneuvering a twin engine boat requires much more than turning your steering wheel one way or the other. It involves throttle manipulations that vary greatly depending on wind and current. These are topics for another discussion, however, as this column will discuss what to do if you lose one of your twin engines. This scenario adds a whole other dimension to operating your boat. Although this scenario is not likely to happen, it happens all too often and most boaters are not prepared to deal with the situation. The following recommendations will help you prepare for that rare scenario.

Flotilla 081-06-08 is based at Coast Guard Station Galveston. The Coast Guard Auxiliary is the uniformed civilian component of the US Coast Guard and supports the Coast Guard in nearly all mission areas. The Auxiliary was created by Congress in 1939. For more information, please visit www.cgaux.org.

Notify the Coast Guard
If you are having engine trouble, you should notify the Coast Guard immediately. This will alert them to the situation before it becomes an emergency, and they can notify other mariners in the area to be on the lookout. Disabled boats can be a severe hazard to navigation, and by notifying the Coast Guard you are being a responsible boater. As you progress toward home, be sure to update the Coast Guard on your progress every 30 minutes. They will need your latitude and longitude, so be sure to have either a GPS or the Coast Guard smart phone app so you can give them your coordinates.

Fuel Considerations
One might assume that two engines would automatically consume more fuel than a comparable single engine, but that is not always the case. For instance, as the chart below shows, two 175-hp Yamahas consume slightly less fuel at most throttle settings than a single 350-hp Yamaha.

If you operate your boat on the principle of the Coast Guard recommendation of “one third of your fuel to go out, one third to get back, and one third as reserve,” you stand a good chance of making it back on one engine. But keep in mind that you will most likely have to operate that single good engine at or near full RPM, and that pushes your fuel consumption up considerably.

Getting on Plane
One of the most important things to consider when purchasing a twin engine craft is whether or not the boat is capable of getting on plane with a single engine. If you can’t get on plane with one engine, that 60-mile trip back in will stretch from three hours to possibly eight hours or more, depending on what speed you will be able to make. A boat that is not on plane is much harder to navigate in rough water. The time to find out if your boat will get on plane with just one engine is before you lose an engine. If a boat has a planning hull, then the manufacturer’s recommended horsepower for that boat starts with enough horsepower to get the boat on plane.

That being said, that lowest horsepower rating takes into consideration the best case scenario of one person aboard with no extra gear. Not much chance of that being the case, is there? So, consider a good margin of error when choosing the horsepower of your twin engine craft. If the minimum recommended horsepower is 175 hp, you might not be able to get that boat on plane with one 175 hp engine if you are loaded with passengers and gear. Take that salesperson up on the offer of an on the water demonstration, then ask him to get the boat on plane with one engine. You need that peace of mind. Once you know your boat will operate on plane with one engine, there are some other things you can do to help get on plane, stay on plane, and get back home safely using just one engine.

Raise the Dead
Engine, that is. Get that dead engine’s lower unit out of the water to help eliminate drag and also help with maneuvering. It will be harder steering the boat with the good engine being offset from center, so any help you can get is welcomed.

Weight Forward
You already know it is harder to get on plane when everyone is sitting at the back of the boat. Outboards tend to squat in the stern and rise in the bow when coming out of the hole. Most boats have a recommended seating chart, and that chart is designed to help you get on plane and safely maneuver the boat at speed. Moving the weight forward is even more important when you are down an engine. It’s not just the passengers you need to move. Move heavy gear such as ice chests forward. Once you get on plane, the passengers may be able to move toward the stern to get comfortable. It takes a lot of energy to get up on plane, but once you are there it takes less energy to maintain.

Lighten Up
If you have shifted the weight forward and you are still having trouble getting on plane, you may need to lighten up. Empty out built-in ice chests and freshwater tanks located at the stern if you are having trouble getting on plane. Water weighs 8.3 pounds per gallon. If you empty out a 30-gallon livewell, it has the same benefit as throwing your brother-in-law overboard (come on, now- lighten up). If you have fish on ice, you can reduce the amount of ice and still keep them cool enough.

Tilt and Trim
In order to come out of the hole and get up on plane you will need to have the trim in all the way. That position helps raise the stern while tending to keep the bow down. Once you have the boat on plane, try trimming the engine out in small increments. This will raise the bow slightly and help reduce drag. Once you are up on plane, do not make any sharp turns, as this may bend the tie bar between the engines. If you have trim tabs, use them to help pop up out of the hole. Once you are on plane, use them to help keep the boat from heeling over to one side due to the offset torque from the one good engine. Apply down tab to the lower side to level the boat and keep you on an even keel.

Summary
A twin engine boat gives you peace of mind that you will be able to motor home safely should you have engine trouble and lose one engine. It is important that the remaining engine have enough power to get your boat on plane, and you should practice getting on plane with one engine so that you know what to do if you lose an engine. If you are unable to get your boat on plane, you can get home by operating your boat in the displacement mode, but it will be a much longer trip. Be sure to have a marine FM-VHF radio in any case so that you can notify the Coast Guard if you have trouble.

Request from Shrimpers
Please give shrimp boats with their gear down a wide berth. Although they are only plugging along at 3 knots, they do not have the ability to maneuver quickly, and their gear extends both far out to the sides and a great distance behind their boats. Look for the day signs used to indicate that the shrimpers are actively fishing.

Request from Barge Tow Captains
Please do not operate between two tows that are meeting or passing in the Intracoastal Waterway. Although the ICW is wide enough for meeting and passing of large tows, it is dangerous to operate between two tows. Give them time to meet or pass before you pass.

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

[10-22-2018]

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