I will say that I've used a straight fire hose nozzle on my clear water pump with rather impressive results. I first learned about the nozzle when we rented a hydroseeder and needed to run some water through the lines to clean them out. I put 500 gallons of water in the tank and "watered the trees" from 150' away! A fleepin' ton of fun! Based on that, I then bought one of the McMaster nozzles for my pump. It's a ex-military portable water pump. Rated at 65 gpm with a 50' lift. I don't know what pressure or what the max lift is. But, it does really well with that nozzle. I wouldn't try to fight a structure fire with it, but I'd take on a small grass fire. The problem that I see is the set up time. The pump requires two people move. Another trip for the fuel can. Hook up the suction hose, set it so it doesn't suck mud. That alone is 5 minutes. Run out the hoses. I can't see this process happening in less than 15 minutes. Not knowing where you are, but in that time, I'll be putting water on the smoking grass because the fire has already moved out of range. If you are serious about the need for fire protection, perhaps get a farm wagon with a 1,000 gallon tank and mount the pump right on the wagon. If the fill tank is prepositioned, you might get your response time down to just 5 minutes. Even then, 5 minutes is such a long time that the fire could be out of control by then. Not my post, but this is my pump:
http://www.steelsoldiers.com/showthread.php?91764-New-Toy-65GPM-Yanmar-powered-freshwater-pump/page2 You have to log in to see the pics, but there are some good ones with a fire nozzle. Note he has the discharge hose kinked in the photos.
A while back we were burning some scrap wood from our barn reno. A gust of wind came up and blew a bunch of embers into the scrap wood pile we were feeding from. Within a minute there was a half dozen smoking hot spots. Thankfully I had a plan in place. We had already filled the atv sprayer with water and had the tree sprayer wand mounted. I worked on sucking heat from the main fire and the mrs drove the atv around putting out hot spots. In case those 25 gallons were not enough I had 6 5 gallon buckets of water already staged to quickly refill the tank. Thankfully, they were not necessary and we got the fires put out within a couple of minutes. Point is, when it hits the fan, you don't have the time to set up the pump. It already has to be standing by.
I second the "Indian" brand fire pumps. I keep one at ready at my off grid cabin.
McMaster-Carr