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Auto Outboard-Trim Systems

Technological advancement keeps you running at the right angle

December 2, 2016
Boat with auto-trim
Outboard-trim systems such as Mercury’s optional Active Trim automatically adjust the boat’s running attitude for optimum speed and efficiency. Courtesy Boston Whaler

The 40 hp outboard on my first boat came with manual trim and tilt. And by “manual,” I mean I had to physically lift the outboard to change its trim angle or tilt it out of the water. It was backbreaking, but I was young.

Outboards have advanced mightily since those days. Engines as small as 9.9 hp now offer power tilt and trim, allowing you to pivot the outboard up or down with the touch of a rocker switch. Before discussing more advanced systems, let’s review the basics of outboard tilt and trim. Most outboards use two ­hydraulic-ram assemblies built into the clamp bracket, both operated by the same rocker switch on the throttle control box. One is for tilting the lower unit in and out of the water when, for instance, you are trailering the boat or want to raise the drives out of the water at the dock. This system comes into play in the upper range of outboard pivot and is not designed for use while underway.

A second, more robust system operates in the lower range of outboard pivot and is dedicated to trimming the engine while underway. This function fine-tunes the ride of the boat. Generally speaking, trimming the outboard inward tends to push the bow of the boat downward. Trimming outward tends to lift the bow. The angle of the bow while underway is known as the “running attitude.”

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By properly adjusting the running attitude, you can maximize acceleration, speed and fuel efficiency. Veteran captains know through experience how to do this, especially when manning the helm of their own boats.

Less experienced ­boaters, however, might struggle to achieve the best attitude, particularly when piloting an unfamiliar boat, leading some marine-engine ­manufacturers to develop the next level in outboard-trim technology.

Evinrude Icon display
Evinrude’s Icon multifunction display allows boaters to control i-Trim and other systems of the E-Tec G2 outboard motors. Courtesy Evinrude

Full Auto

“Figuring out how to ­properly trim any boat involves a learning curve,” says Jason Eckman, product marketing manager for Evinrude Outboards. “That’s why Evinrude decided to develop and offer i-Trim as a standard feature on all E-Tec G2 outboards. It’s a system that can automatically trim the boat for you.”

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Evinrude is not the only outboard brand to offer an automatic-trim feature. Yamaha Outboards was first with its Trim Assist, built into the optional Helm Master system. Mercury Marine also introduced its optional Active Trim system earlier this year.

Each system varies in its application, but the principle behind each is the same: automate the outboard-trim function to optimize performance and free the captain from having to fiddle with the trim switch or watch the trim gauge, so he can maintain a better watch while underway.

I have had a chance to use the Evinrude and Yamaha systems and have found that they do an outstanding job of trimming outboards in relatively flat water. In choppy seas, however, I have needed to override the automatic function at times by trimming in to bring the bow down, allowing the bow to knife through the waves and smooth the ride. Overriding these systems is simply a matter of pressing the trim switch, which temporarily disables the auto function.

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Mercury Marine optional Active Trim system
A special control pad allows you to activate and adjust Mercury Marine’s optional Active Trim system. Courtesy Mercury

Sophisticated Sensors

Auto-trim systems use a number of sophisticated sensors to determine optimum trim.

For example, Yamaha’s Trim Assist senses revolutions per minute and outboard angle to automatically adjust trim for any engine speed.

Mercury’s Active Trim uses a ­patented GPS-based system to control the trim in accordance with boat speed over ground and engine rpm. “This approach avoids potential problems such as the engines trimming up (instead of down) if the propeller breaks loose in a hard turn,” says a Mercury news release on Active Trim.

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Mercury rolled out its Active Trim system at the 2016 Miami International Boat Show in February and at several subsequent consumer demonstration events this year. “Every single person who drove Active Trim said they were going to put it on their boats,” says Steve Fleming, communications director for Mercury.

In addition to trimming the boat for optimum performance while underway, the systems from Evinrude, Mercury and Yamaha also readjust the outboard angle as the boat decelerates and/or returns to idle speed.

For boating anglers who might venture into shallow water, it’s important to know that none of the systems can detect water depth, and they will not trim up automatically in shallow water. In such cases, the captain needs to override the system by trimming the outboard manually to avoid striking the bottom with the propeller or skeg.

Yamaha automatic Trim Assist
Yamaha’s automatic Trim Assist is integrated into the electronic controls of the optional Helm Master system. Courtesy Yamaha

Personalized Settings

Some boating anglers might like the convenience of automatic engine trim but would prefer greater control in determining how and when it occurs. To accommodate this desire, systems such as Yamaha’s Trim Assist let captains pre-program points and trim angles along the rpm curve to suit their vessel and style of boating, using the Yamaha Command Link Plus ­multifunction display.

Mercury takes a slightly different approach, offering five pre-set trim profiles to accommodate different types of boats through the Active Trim control pad. You can also customize the profiles to suit your driving style and/or compensate for changes in boat load or sea conditions.

Compatible Configurations

Evinrude has integrated i-Trim into all E-Tec G2 outboards (including the new 2.7-liter V-6 series), and the system functions in single- and multiple-outboard installations with up to four or more engines. Evinrude’s Icon touchscreen display provides control of i-Trim.

Engines compatible with Active Trim include Mercury 40 to 400 hp four-stroke outboards and OptiMax two-stroke outboards with SmartCraft. Active Trim is also available for all MerCruiser gas and diesel sterndrive engines with SmartCraft. Retrofits are available for engines already in use. Active Trim functions with one to four outboards.

Yamaha’s Trim Assist is available only with the optional Helm Master system, which works with Yamaha’s 4.2-liter V-6 and F350 V-8 outboards in triple- and quad-engine installations.

Some boating anglers might pine for the good ol’ days, but not me, especially when it comes to outboard tilt and trim. Automatic-trim systems are just one more way that outboard builders are making boating more convenient, ­efficient, safe and fun.

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