Using a Trolling Valve

Salmon fishermen are very particular about their trolling speed to the point of being superstitious. Too fast and the gear is straining at the line release clips on the downriggers. Too much speed will cause the downrigger wires to sing and trail the boat at a shallow angle, not holding the lines deep enough to reach the fish or generate the proper bait motion. Too slow and the fish are unlikely to strike a lure hanging dead in the water. Constant adjustment leads to another problem–lines getting tangled. Driving the boat I monitor my speed by watching the GPS computed speed, watching the water move past the side doors, as well as listening to complaints from the back deck. Too slow or too fast and the fishermen start to complain… Loudly.


The throttle and driver station of the Nordic Quest

The Nordic Quest has an excellent trolling mode, the new Cummins Mercruiser Electronic Throttle and Shift Control, or ETS. It is able to move the boat at the 1 to 2 knots speed greatly preferred by salmon fishermen. Fuel consumption is surprisingly low as well when you realize you have a 500 hp diesel engine pushing you along.

There are some things about using the ETS that tend to catch some folks by surprise. I can fully understand this, as the special features do not operate as you might expect from your experience operating the engine in its normal mode.

The first thing that seems odd is that the engine will remain at idle speed, about 600 rpm, regardless of throttle setting when in trolling mode. This makes it seem like nothing is happening as you adjust the throttle. The trolling valve operates by changing the coupling of the engine to the propeller shaft, applying more or less power. So you must operate trolling valve without the feedback of watching the gauges or feeling the changing rumble of the engine through the hull.

A second issue is that the trolling valve only seems to begin operation at a higher setting of the throttle. I find that I need to slowly push the throttle far forward until I feel and hear the engine grab. I then immediately pull back about half way. Through some experimentation I have found the correct throttle position for 1-2 knots, where the complaints cease from the fishermen on the back deck. Experimentation is the key here, you have to try it a few times to get the feel of it. Do this while the fishermen are preparing their gear, before the gear is in the water.

Nordic Quest Dashboard

The dashboard and navigational display of the Nordic Quest, note the engine control button cluster at the far lower right, with troll gear engaged!

The Cummins Mercruiser trolling valve is engaged as follows…

  1. Place the engine throttle in neutral.
  2. Press the troll button on the ETS control panel. On the Nordic Quest, this is the small black button cluster found left of the throttle at the far right of the recessed dashboard at the helm. The LED in the troll button should illuminate.
  3. Smoothly push the throttle lever forward until you feel the engine grab. This is fairly subtle, but quite distinct once you encounter it. The folks on the back deck will see the swirl of water at the stern.
  4. Immediately pull the throttle back about halfway to the position that achieves the desired speed.
  5. Adjust the speed as required with the throttle; this will take constant monitoring as wind and current conditions change.

To achieve the correct speed a few adjustments will be needed. These are done very slowly, making very small adjustments to the throttle position and waiting a minute or so to observe the results. Nothing happens quickly in troll mode, changes in speed or response to the rudder. Remember that throttle position, you will want to return there every time you return to using the trolling valve.

With the Cummins ETS you can leave troll mode by simply advancing the throttle in forward or again moving the throttle to neutral then press the troll button again and the indicator LED should go dark. Placing the engine back in gear will reward you with that comforting, smooth diesel rumble underfoot as you move forward.

Used properly the trolling valve on the Nordic Quest will let you hit just the right speed you want for great salmon fishing. Practice a bit and carefully observe the results to figure out just what you need to do. Once you have it you will find that it is pretty straightforward.

Now go catch some fish!

About Andrew Cooper

An electrical engineer living and working on Mauna Kea, Hawai'i. Webmaster for the website. Sometimes the first mate/deckhand/launch driver/anchor detail/cook/dishwasher and mechanic aboard the Nordic Quest.
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