Tell Me Everything Page 3
|Tell Me Everything|
| Part 3
By Tim Clark — January 2002
The engine load parameter’s primary use is to help you properly prop your boat. According to Wessinger, Cummins will typically prop a boat so that at the engine’s maximum rated speed it will run at 90 to 94 percent of maximum load. This allows for the weight in equipment and toys you’re likely to add to the vessel. Later, if you notice that your load reaches 100 percent before the engine attains maximum rated speed (thereby shaving knots off your boat speed), you know you have a problem such as a dinged prop, excessive onboard weight, or heavy hull-bottom growth.
Another parameter useful for adjusting systems related to your engine is throttle position. Say one day you find that your boat is not running as fast as she should. You check your throttle position and learn that fully forward it’s only showing 78 percent, meaning that it’s commanding the engine to run 22 percent below its full duty cycle. At once you’ve isolated the problem in the throttle system and know that it’s in need of adjustment.
You can derive useful day-to-day data from the fuel rate parameter, which is a great illustration of the convenience of built-in electronic monitoring. Without having to compromise the integrity of your fuel lines by installing separate flow-metering equipment, this data, consulted along with boat speed information, will enable you to run your very own sea trial and precisely determine the most economical cruising speed for your boat.
You can also use fuel rate and boat speed to estimate range. On a special Trip Fuel Economy Page, the Cummins unit displays the engine’s total hours and fuel consumed on the left and trip hours and fuel consumed on the right. The totals accrue throughout the engine’s life, but the trip values can be reset at any time. After just once starting with a precisely known quantity of fuel onboard, you can use the Trip Page combined with fuel rate and boat speed data to keep tabs on your fuel levels much more closely than with an F to E gauge.
When it comes to trouble, electronic displays are far more articulate than their mechanical predecessors. If any of the safety-related readouts–displayed or not–creep beyond their programmed parameters, an alarm will sound and "Active Fault Present" will appear as a banner across the screen. By going to the Information page, you’ll find how many alarms are active, one or more three-digit fault codes (to refer to if you consult a Cummins technician), a textual description of the fault, and even recommended specific responses such as slowing to idle speed or heading for the marina for repairs. (While some manufacturers’ ECMs will automatically derate an engine if they detect certain problems, Cummins has elected to leave the decision up to the skipper, feeling that in certain circumstances, such as extreme weather, it may be more important to make headway than preserve the engine from damage.) Moreover, the system also polices itself, sounding an alarm if it detects a malfunctioning sensor.
We’ve all been told that thanks to computers and the Internet, we live in the Information Age. Electronic engine data displays–with their tiny processors linked to an array of sensors and engine ECMs in a mini computer network–are in lockstep with the times, providing an unprecedented wealth of information at the helm.
Cummins Marine Phone: (800) 343-7357. Fax: (800) 232-6393. www.cummins.com.
This article originally appeared in the June 2003 issue of Power & Motoryacht magazine.