We will be retiring soon and purchasing a small trawler to cruise the Bahamas. We have been trailering a small Grady-White outboard (weighing about 2,500 pounds), and running it from West Palm Beach to Hopetown, Abaco, every year. In the near future we plan on towing this same boat from Baltimore to the Bahamas with our trawler. I will beef up the bow area of the Grady to make it suitable for towing, but my question lies with the trawler.
We are currently looking at a Mainship 350 with twin diesels. Towing the Grady will cause not only a decrease in speed but also a change in the Mainship’s rpm. As this is a long tow, I want to make sure we are running as efficiently as possible, as well not harming the engines. First, can this be done? And second, if feasible, then I am thinking of two sets of props. One set for towing, and another set for our months of cruising in the Abacos. This would also provide us with a spare prop for each shaft, even if not the same pitch or diameter.
Can you validate or offer other ideas or suggestions? Joe Borrison Rockville, Maryland There are some variables to consider before expressing a complete opinion on this question. The answer hinges mostly on the motors. Older, mechanically timed engines were designed to run at a narrow range of rpm and load. In this case, it would not be good if you could not reach cruising rpm but the motor remained under high load. In this instance, I would look at the exhaust for black smoke, signaling that the amount of fuel supplied is not being burned, because the engine speed is not high enough. Also, I would expect that the operating temperature would be rising. If, on the other hand, you are able to reach rpm and the engine is not smoking black or getting beyond the operating temp as specified by the manufacturer, towing may be feasible. Remember that fishing trawlers pull great loads without problems as well as traveling long distances without towing loads.
If the engines are computer-timed modern engines and of sufficient horsepower, I would think the idea a bit more feasible as the engines can run under a greater range of loads and rpm without damage. In addition, modern engines can accurately monitor load percentage, fuel burn, and boost pressure to assess whether the load is compatible with the propulsion.
To address the question directly, I do think it is possible, although it would require extra diligence concerning weather and fuel range. I do not much like the idea of resizing the props for towing, as you would be decreasing pitch to increase engine speed. This could have dramatic consequences in extreme conditions. Again, this all depends on the horsepower available, so no reasonable answer is possible without more information and some live testing at sea. Capt. Larry Crouch Galveston, Texas