*THE HULL TRUTH is the world's largest FREE network for the discussion of Boating & Fishing. Whether you're researching a new boat, or are a seasoned Captain, you'll find The Hull Truth Boating & Fishing Message Forum contains a wealth of information from Boaters and Sportfishermen around the world.
Welcome to the updated THT!
If you are having trouble signing in, please email feedback@thehulltruth.com with your username and we will help you. We thank you for your patience as we help you access the new site!
Random Quote: Fishing "A pleasure disguised as a sport"
It looks like either the ParMax 3 or 4 but I can't find out if you can use them with salt water for washdown/baitwell. Anybody know? Also for your water inlet I'll be using bronze but is it better to use a scoop style or just a flat thru hull style for the water pickup? This is all new installtion boat has nothing so I'll be going thru the hull for water. I know make sure it'son the trailer when I drill
All of the internal parts on the pumps are plastic, so they don't care much about salt. What will eventually fail, if my experience with washdown pumps hold true, will be the seal between the pump and the motor. The motor will ingest water, corrode, and seize. It seems it doesn't matter who's pump you buy other than some do it sooner than others.
Get all the pump you can buy. The Par Max 4 delievers 4.3 GPM open flow and the Par-Max 3 delivers 3.5 GPM open flow, roughly a third less. The difference in price between the two models should be about $30 no matter where you buy one.
When you go to wire that pump please keep in mind that it is a large power consumer. When its putting out its full pressure it will be sucking down electrons at a rate of somewhere very near 6 amp/hours. That makes it a great candidate for thick wire and strong connections - nothing else will do. It will need its own fuse or circuit breaker and if you're smart you'll also put a switch in the line.
In fact let me give you some further advice that may make a big difference in how satisfied you are with your system. You seem to have a good handel on the plumbing but I'm gonna go over it stemto stern first as well just for the other guys who might read this and need the information.
To scoop or not to scoop? Well, a bronze thru hull will cost you around $10~15 for one in 3/4" and a scoop will cost you about twice that much. The scoop will offer a little more resistance going thrugh the water, but not engouh to make any difference in fuel economy so it doesn't matter. It will, however, destroy any chance of a transducer mounted down stream of it (thru-hull, transom mount, or even an in-hull that is mounted behind it) from working. The scoop type will provide suprisingly stong pressure water to the system when the boat is underway but it won't have any effect on the water pressure at the hose on anything other than a centrifugal pump. The Par-Max pumps are not centrifugal, they are diaphram pumps. Scoops leave something stickingout to be damaged if you run aground, straight thru-hulls do not. So how often do you run aground? In the end the scoop is probably more desirable, but its not really at all necessary. If you run at plaining speeds a lot then the scoop will be easier on the pump, but not because it adds pressure no the inlet side, but actually because of an inherent problem with straight thru hulls as inlet. The faster you go the less the pressure at the hole with a thru-hull. So the faster you run the harder it is for the pump to suck water. I'm not gong to go into why other than to refer you to Bernoulli's Law and tell you its the same thing that allows wings to work.
So the water gets inside the hull and now you have to give yourself a way to keep it out of the hull if something goes wrong. You need a seacock. A seacock is a valve that attaches to the hull and the fitting. In the event the fitting gets knocked off you still have the valve and can shut off the flow of water into the boat. You could use a simple ball valve but it will not do as much as a seacock because it can't shut off flow into the hull, only in the system after the let. There is also the fear by some that you cold accidently kick or hit a valve and break it off the stem. That one is a joke, but neverermind, seacocks are better. I use a valve myself. Once again, for a small boat keep this 3/4".
You have to drill the hole in the bottom of the boat in the aft section (back half, but in this case its more like the back third or so). Its is the only part that can be expected to be in the water so its where you need to go to get your water. Nothing special about the mounting. Don't go overboard with the sealer and don't drill the hole any larger than necessary to get the stem of whatever your use through the hull. That's all.
Next you need hose. I use plain 3/4" radiator hose, available at every single auto parts store in the nation at whatever price they can get out of you. Do not, however, buy your hose clamps at an auto parts. Get them at a large hardware store and get them from where ever the section is that they sell submergable pumps. The reason is that the hose clamps usually found in auto parts stores, and in the bins of a lot of hardware stores, have stainless straps but common steel screws. The screws will rust away and freeze up the clamp, finally leading to failure. The clamps they use for submergable pumps (the ones that go down water wells) are completely stainless.
Now, your hose goes to the pump. Mount the pump in a dry area. I do not care what it says on the package or in the Instructions, none of them can stand to be so much as splashed. I'll say it again, mount it in a dry place. When you mount it do so such that the pump part is down and the motor above it. It actually will let the thing live about a year longer no matter who's pump you use.
Try to find a pump that has 3/4" inlets and outlets if you can. Oh, I should say why. The standard size of the fittings on the end of a hose, the female part you screw onto the hose bib and the make part where you will screw on one of those pistol-grip nozzels, are all 3/4" and if you want maximum flow out of the pump your hose will be too (I have to admit that I cheat here and use a 5/8" 15' hose on mine). By sticking with 3/4" from one end to the other you do not loose pressure by going through reducers or adaptors when moving up or down in sizes.
The outlet side of the pump will either have the hose hooked directly to it or will be plumbed to a water outlet somewhere on the hull. Water outlet come in two types, male and female. You want a male if you use one and if it comes with a plastic cap go to the plumbing section of any Lowe's or Home Depot and they will have bronze replacements. As they used to say, "Get you one."
Now you have to wire the pump. This usually isn't applicable to CC boats with their batterys under the console, but they are in the minority. Here is the mistake most guys make. They will go to their fuse panel and if they find they have an open fuse they will take it over and run a line from it to their pump. Most of them will put a switch in the line somewhere and that is a smart thing to do. This will work just fine. There is, however, a betterway.
You have your water pickup in the aft third of the boat and in fact its probably within inches of the trasom. Your pump will be mounted somewhere nearby, usually against a bulkhead, stringer, or maybe even on the transom itself. It is also likely that your batterys are mounted somewhere the aft section. Let's say the boat is 20 feet long. Fuse panels are usually somewhere near the steering wheel and the steering wheel is usually somewhere around the middle of the boat. So the distance between the battery and the fuse panel is probably around 10 feet but it takes 15 feet of wire to get there because of the twists and turns and such. Also, keep in mind that there are two wires, the positive and negative, so now you're looking at 30 feet of wire. After it gets to the fuse panel, and maybe a switch, it then has to run back to the aft end of the boat where the pump is, so there's another 30 feet of wire for the return trip. How much DC power loss do you think there is in 60 feet of wire? The correct answer is 'quite a bit.' That power loss will equate directly to reduced water flow from your wash down pump.
Here is the better way to wire most wash down pumps. Buy a relay. Generic ones can be bought at Radio Shack or from most auto parts places. They cost about $5. Put it back near the pump and then take a fused power line off of your battery switch and run it directly to the relay. Then run the positive line from the pump to the relay's output side. Ground the relay. Ground the pump to a small aft bussbar (another $5). Now you can go dig around in your fuse box and find a line, or you can even tap into an existing power line (because we're hardly going to use any power at all, less than an instrument light uses), and get power to run to your On/Off switch for the raw water. From the switch run that single wire, and it can be very small wire. As a side note I do not use anything smaller than 16 guage on a boat myself, but you could go even smaller on this one if you wanted to. Run this wire to the relay and use it to activate the relay. It will require something on the order of a quarter of a milliamp to operate.
By running short wires to feed the pump through the relay you can save yourself the considerable expense of large wire (60 feet at 6~8 amps draw would require roughtly 10 guage wire) but more importantly you'll deliver more power to the pump, and that results in more water out of the pump.
There is no particular reason to have a valve on the outlet side of the pump. You have a switch which will act as an effective valve. Most of the pumps have pressure switches built in so just turn it on and leave it on until the end of the day. In that reguard its not a bad idea to put an indicator light on the switch, just so you know at a glance when its on and when its not.
One last thing, and many boats simply do not have much room for this one, but an accumulator tank might be in your future. Water in essentially incompressable so the difference in your pump running when you draw water and it not kicking on just yet is really just a matter of how much your hose expanded under pressure. The pump will basically be running any time you are drawing water, be it for just a second or for minutes at a time. That means that the pump will cycle just as often as the water is used, and that may very well be a lot, particularly if there is a leak anywhere. However, if you can put a sealed chamber somewhere in the output side of the line and that chamber is full of air that air will be compressed to equal whatever the waterpressure is. It will also be displaced by some of the water as it is compressed. So if you have one of these things the pump kicks on (even if the nozzel is shut and now water is being used) and it pressurizes the system. In doing so it blows some water into the tank and the remaining air in the tank gets compressed the the same pressure as the water, obviously. Then the pump shuts off. Now if you open the nozzel water will come out, but it will be comming out of the tank. The pump won't kick on again unless enough water has been removed to all the pressure to drop in the system but that pressure is being maintained by the air trapped in the chamber. The bottom line is the pump cycles a lot less and because start-up power consumption is the pump's highest you save electrical power, you cause the pump to live longer (sort of, actually it is corrosion that will probably kill the pump eventually), and even out the pressure spikes you'll see in the line. For whatever its worth the ones they sell for $30~45 that hold about a quart of air/water are woefully undersized in my opnion. I put one in our boat that is made of stainless steel and holds just over 2.5 gallons. It was part from a commercial air conditioning system and cost me twenty five bucks. Look around.
That's about it. or at least that's about all that comes immediately to mind. Your boat is on a trailer so no matter what anyone tells you don't be worried about a cored hull. Your boat doesn't have one. Don't be tempted to use that thru hull as some sort of ground for your electrical system either. It was not meant to be a ground and you should not use it for a purpose for which it was not intended. There may be a temptation to put a strainer on the inlet side of your system. If you buy a scoop the width of the slits in the inlet are small enough to keep anything really harmful out and if you lost the use of the thing for a day because of a clog it wouldn't be the end of the world to have to wait until you could unclog it. So I wouldn't bother on a small boat.
Just to be safe use 5200 below the waterline if you like. Its not really necessary but if it gives peace of mind then its worth it. All tinned wire of course. I crimp, solder, seal, then shrink fit myself, but others do less with success. Did I mention keep the pump dry?
A big thanks to Thom. Once again, his ideas will save me some time and money.
Another thought for a new installation. After the seacock, I installed a 'T' to a valve with a length of hose to the bilge. In an emergency, I can close the seacock, open the other valve, and use the washdown to help pump out the bilge by pointing the washdown hose overboard.
How much DC power loss do you think there is in 60 feet of wire?
Don't know, but does it really matter? The maxiumum run is only thirty feet - 15' of positive wire from the battery to the fuse panel, and 15' of positive wire from the fuse panel to the pump; ground run is irrelevent as far as voltage drop is concerned. If both runs have appropriate sized wire, any drop should be negligible ... I think.
A big thanks to Thom. Once again, his ideas will save me some time and money.
Another thought for a new installation. After the seacock, I installed a 'T' to a valve with a length of hose to the bilge. In an emergency, I can close the seacock, open the other valve, and use the washdown to help pump out the bilge by pointing the washdown hose overboard.
I agree beachblitz...any time you can give something like a pump a second duty as a bilge pump I will do it. For those that don't want to go looking for fittings to make up thier own adaptor they can get one fo these for their system:
I'm going to install one in the raw water side of my FWC for flushing, winterizing and act as a bilge pump and another in my raw water washdown for flushing, winterizing and act as a bilge pump. Of course YMMV.
Great instructions Thom...as usual. There is only one thing I would differ with you. I don't open the sea cock till I'm ready to use the washdown. If I'm underway, or my attention is elsewhere (fishing, etc) and you pop a leak you won't know till the bilge is full - and that's a heck of a time to find out. This way I only open it to do my washdown and then shut it back off before heading home. I just feel a little more secure that way.
Curmudgeon, yep, all the wire counts. The negative wire is just as much a power carrying part of the loss in the circuit as the part before whatever device you are powering. I know it sounds counterintutive, but its how it works. Think of it this way, if you installed something, anyting at all, in a DC line and used wire that was a little bit to small the wires would get hot when you ran whatever the thing was. Both the positive and negative wires would get hot. That heat is the easiest measure of power loss in the circuit, and you'll notice it emits from both wires. One of the easiest ways to reduce power loss for things aft is to simply put a second negative side buss bar back around the transom somewhere. Anything that needs to be grounded aft goes to it and saves a lot of wire run ($) and attendent power loss.
Mole, that is a very good idea, to leave the seacock shut until the water is needed. I don't do it with mine but I have warning lights wired onto the bilge pumps. So if there is more than about an inch of water in the bilge I know about it pretty quickly. Still, your practice is the better one, no doubt about that.
Thanks Thom for all the advice and tips. I knew this would be a can of worms once I started this boat project but hopefully it will be worth it in the end.
Washdown 
Of course YMMV.
