Know the Flow

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The Livorsi Water Flow System gauge illuminates a bright red alarm light to alert you to a restriction in your performance-boat’s cooling system.

It’s a Sunday afternoon and you’ve got the water to yourself. After checking the gauges and seeing that everything is okay, you nail the throttles on your stepped-hull performance boat. As the speedometer edges past 80 mph, the dreaded audio alarm blares from one of your motors. You pull back the levers, ease to a stop, and assess the situation.

Discoloration of the exhaust header on one of your motors is the first telltale that the engine has overheated or at least been running at a higher-than-optimal temperature. You’re baffled. The strainer isn’t clogged and the water temperature and pressure gauges are reading normal.

The problem is that even though the gauges read correctly for pressure and temperature during your high-speed run, they couldn’t tell you how much cooling water was actually flowing through the engine.

That’s why Livorsi Marine has come out with its Raw Water Flow System. It’s a paddlewheel sensor that’s installed in-line after a strainer or pickup to read how much water is actually flowing to the engine. It can alert you to a restriction in the pickup or strainer or even to a clogged exhaust riser or intercooler on supercharged engines.

“A lot of engines have water pressure, but they don’t have enough flow,” said Mike Livorsi, president of Livorsi Marine, the leading supplier of gauges and controls to the performance-boat market. You can see the Raw Water Flow System in the Livorsi Marine booth, #1226, at IBEX 2011, in Louisville, Kentucky.

Ever since the modern era of stepped hulls began in the mid-1990s, there’s been an issue with water flow, because the steps aerate the water that’s sucked into a drive or remote-mounted pickup on the bottom of a boat. When water is aerated, not as much flows through the engine, which means the engine can get hotter than you’re aware of, because the pressure and temperature gauges are still reading at the appropriate levels.

“The faster the boats go, the more aerated water you get going through the system,” said Livorsi.

Livorsi Marine is a sister company to Custom Marine Inc., which supplies stainless steel exhaust headers for many engines in the Mercury Racing line. One of the primary reasons that headers become discolored or brownish looking is that the headers are not getting sufficient cooling water.

The Raw Water Flow System is an additional monitor that alerts an owner so he can prevent that from happening. The system retails for $429 complete.


Parts in the system’s kit include a processor board (left) and a wiring harness. The bronze paddlewheel housing (right) is installed in a cooling-water line after an intake or strainer.

The kit includes a paddlewheel sensor that’s installed in-line after the sea strainer. We covered a similar system from Groco Mechanical Laboratories, the Strainer Service Advice (SSA), in the Rovings column of Professional BoatBuilder No. 131. Livorsi purchases the sensor from Groco, who in turn buys the gauge for its system from Livorsi. Groco is targeting diesel-powered engines and accessories, while Livorsi focuses on the performance gasoline-powered market.

In addition to the paddlewheel sensor in a bronze housing, the Livorsi kit includes a 2 5/8″ (67mm) gauge, Processor Control Board (PCB) and wiring harness. Hose sizes range from ¾″ to 3″ diameter (19mm to 76mm).

To make the system universally applicable, Livorsi designed it to measure water flow through an engine’s rpm range. You calibrate the system at idle and at wide open throttle. If the PCB reads a difference of more than 20% throughout the rpm range, a bright red LED warning light illuminates in the middle of the gauge, and there’s an optional audible alarm.

For best results, install the sensor housing with at least 12″ (305mm) of straight plumbing before and after to assure the most consistent flow. The processing board must be located within 24″ (610mm) of the gauge. The board must also be connected to the tachometer.

To calibrate the Raw Water Flow System, start with the engine at idle and the gauge pulled out from the dash far enough that you can reach the momentary switch on the back of the instrument. Press and hold the switch for three seconds, and the LED light on the gauge will flash three times and then blink slowly. Press the switch again to accept the idle-speed flow data.

Then calibrate the system at wide open. The engine must be under load, so you need a big enough area to run with the throttle levers pegged for 15 seconds. The LED will flash at a faster rate. Once you’ve run at least 15 seconds at full throttle, push the momentary switch to accept the full-throttle data. After the processor has stored the full-throttle data, it will switch from calibration mode to monitoring the water flow. The system must be recalibrated if you install bigger motors, or superchargers on your current ones.

Livorsi Marine, 715 Center St., Grayslake, IL 60030, USA, tel. 877–548–5900, 847–752–2700,