Deck wash was the first thing i bought for my boat.  the bigger the better!  i think i went for 19 litres per minute at 70 psi???  wonderful!  trips to monkey mia nol longer result in smelly boat, only smelly people now!

 Whitworths sell deck wash kits possibly worth a look.  On the boat I just brought it has a rule 2000 bilge pump bolted on the transom pumps a fair stream of water out of a 25mm pipe.  I haven't used it slot yet but it seems to work well.  It's not a jet but more like a high volume of water.  I could probably fit a nozzle to increase pressure when it's wanted

Probably go with the rule style bilge pump option , as a much better flow/volume of water plus you could also set up a live bait tank from it, plus I have had a couple of specific deckwash pump set ups now using name brand pumps such as johnson and been lucky to get a year out of them & they aren't cheap!  

go for the highest pressure and best quality you can afford - i have a jabsco 70psi (which sounds impressive!) but its prob about the minimum you would want in pressure -

cheers for the imput guys

Jamey: curious about the rule bilge pump option ?...really just don't understand it

from what I can see rule only do bilge and not "self priming" deck wash type pumps.  maybe I just couldnt find it on the website.

how does this option work without having a bilge pump bolted onto the back of the boat?

I guess more to the point I would have thought : high water flow with high pressure > low water flow with high pressure > high water with low pressure > low warer low pressure.  

Is this right ???

ATM I have a crude set up with a 1cm SS tube bolted to the back of the boat facing forward. (conected to the DW hose)  when travelling I get water  from the hose ...works OK but find this hard cos U have to travel at speed to get any type of pressure (hard to wash down and travel in bad weather.)

Very important to get good pump biggest you can afford and make sure it's a saltwater pump not a freshwater one.jabsco pumps wash down kit, type this into Google.Jabsco are a good quality pump.

A high volume bilge pump will kill a deckwash you can either mount on transom or make an ali bracket that you drop it into the water that clips over your transom if you dont want to permanently mount it.

I have spent too much money on jabsco / johnson pumps that dont have the output and last less than  a year, when you can buy a 3000 gall per hour  rule type pump for much less than a third of the price on ebay, that can be used for a variety of functions as well & if it poops itself its easy to replace and reuse bracket, mind you the one I have has lasted much longer than the far more expensive option.  

I've got mine setup with a pick up on the transom, works well.

I did kill the first one though with the pickup constantly feeding into the pump even when it wasn't turned on. Blew the seals out of it.

With the second one I've installed a manual valve in the line between the pick up and the pump. Just switch the valve on when you're going to run the pump.