CO Levels When Tubing - 04/23/2008

CO readings were taken from the inflatable at different distances and speeds.

With the advent of tubing the USCG and ABYC wanted to find out exactly what were the CO levels for people tubing from a tow boat powered by a inboard gas engine. So several years ago they teamed up to test the levels of toxic CO gas to which a wake boarder or tuber would be subjected.

The test boat was a 19’ Correct Craft with 350 hp V-8 inboard engine.

The USCG and the ABYC (American Boat and Yacht Council) have both done investigations within the last few years that shed light on a problem that most boaters don’t think about when it comes to engine exhaust CO poisoning. First, CO is more extant than you may think under normal operating conditions.

The inflatable is serving as the vehicle to hold the two CO meters. Look closely at the top and the bottom of the 2x4. They are affixed at 2’ and 5’ above the water.


The monitoring inflatable underway collecting CO emissions data at speed.

Monitoring tender shown at low speed behind the ski boat with gas inboard.

A team made up of both USCG and ABYC personnel discovered during tests that CO concentrations of 35PPM+ when the monitoring unit was 20’ behind the tow boat going 7.5 mph or less. The results of the tests are as follow—

The USCG/ABYC tester took 1964 data points, as the boat swung into the wind, off the wind, down wind and at numerous speeds. What you see in the charts above are the average PPM (parts per million) of CO and the “peak” readings. You can see that close to the boat, 2’ off the water, are the highest – and potentially dangerous – concentrations of CO at low speeds.

The USCG/ABYC team concluded that CO levels 20’ behind the boat were high enough to affect children tubing. But the most alarming concentrations of CO were in the back seat of the tow boat itself, where the USCG/ABYC said the levels there were “high enough for cause for concern.”

Ironically, it turns out that the most dangerous place to be from a CO standpoint, is in the back seat of the boat at low speed.

To read the complete USCG/ABYC “Safe Distances” report, click here.