We fit damage control (crash ) pumps to all our yachts. These are plumbed with a single line throughout, and Ts with valves in each watertight section. Although the pumps are self priming, the slightest leak, especially to the forepeak, and they won’t draw. So a periodic test is a good idea.
What you see here is the output on a test with the engine turning 1200 RPM, and the 2″/50mm speedometer transducer pulled from the forepeak bottom. The Pacer hydraulically driven pump could just keep up with the flow. When the forepeak was dried out, and flow sputtering, the dry pump alarm sounded (running the pump dry is hard on the shaft seals).
Good test results.
Posted by Steve Dashew (August 16, 2011)
August 16th, 2011 at 4:23 pm
Steve. We are installing a new engine and will be adding a damage control pump. What type of pump do recommened or have the most experience with? We looked through your crusing encyclopedia for a reference and we’re not able to find one.
Thanks.
Mike
August 17th, 2011 at 2:30 pm
Hello Mike:
Which p ump is best depends on engine type and if you have a means of driving the pump other then PTO belts. Assuming not, then you are probably going to end up with an impeller pump from Jabsco or Johnson with an electric or mechanical clutch. If you have hydraulic ower, then you can look at Pacer and their competitors. Our real world experience w ith these iz zero, we are very happy to say.
August 16th, 2011 at 7:27 pm
Hi Steve,
You note the single line with Ts in each compartment. How do you switch the Ts? I am wondering if survey requires switching of the Ts from outside the compartment. Personally, I think manual switching would be OK but I can see the difficulty in a flooding compartment.
August 17th, 2011 at 2:25 pm
Hi Richard:
Each T’d pick up has its own valve, and only the valve from the compartment being drawn from has its valve open. We normally leave the engine room open and all others closed since this is the area most at risk.
August 24th, 2011 at 9:44 pm
Steve,
Do I understand your post to mean that your damage control pump protects you from a 2″ holing but not much more? Or would it pump a lot more if the engine were running harder?
August 25th, 2011 at 3:26 pm
Hi Bob:
Hole size protection depends on RPM, pressure drop in the suction line, and distance below the waterline. But the basic answer for us is two, maybe three inches max, with the best bet on the smaller end of the size range.
August 26th, 2011 at 6:39 pm
Bob,
I would like to add that a 2″ hole allows a tremendous amount of water into a boat. People tend to underestimate the volume from a hull breach and think that bilge pumps will help. In reality I have never seen a bilge pump system that could handle even a moderate hole absent a crash pump.
A 2″ hole will allow in the following:
77 gallons/min at 12″ submersion
109 gallons/min at 24″ submersion
133 gallons/min at 36″ submersion
These are actual rates, not the nominal ones bilge pumps are rated in.