What is the difference and will they interchange?

I know there has been lots of discussion, there is a GM pump,(Saginaw?) that is same. I think people swap the reservoir and the pressure relief valve over.

have swapped several, they claim the marine one(made by AGR) have a bearing instead of a bushing inside, I have never taken one down to see, I bought the marine one from AGR for the checkmate as was having a issue with the hyd steering and was chasing it(did not fix it). but on a few others I bought a truck pump, swapped over the pressure relief valve, spring and fitting and all have worked fine, was told by AGR they would not hold up long term so ????

Ayuh,... Ditto here,... The saginaw pumps are pretty much the same, 'n will retro-fit, so long as ya use the pressure check valve outa the marine pump,...

Difference ? about 300 bucks

I bought a used one off of a 86 Astro Van about 15 years ago for an Arneson retrofit. Still works great!

I ran an automotive one on my 540's a few boats back, I was out of town and in a pinch. I swapped the relief valve and ran the boat for 100 hrs without any problems and sold the boat. Never gave me a problem. Funny thing is, after the incident I never thought about it again until this thread.

Where you at? I have two on a shelf I have no use for.

Marine Has higher pressure. But all you have to do is pretty much swap the pressure relief valve and spring. I made a how to do it thread, either here or PBN. like me find it.

EDIT: It is on PBN and since OSO will block the link like this
http://forum.***************.com/general-powerboat-discussion/4167-how-replacing-your-power-steering-pump-mercruiser-$60.html

Go over to power boat nation, > general discussion> How to: replace you power steering pump

Or copy and paste this in google and it should pop up "power steering pump 92nsx "

Excellent info. Saving in the diary for when the day arrives!