On past boats I always had an electric prelube system plumbed up. I may do it with these also but for now I just want to get engines fired after winter storage.
I want to pull the fuel pump relay on my hp 500 efi and crank the engine for a while to prelube engine after winter storage. If I pull the fuel pump relay will there be enough fuel pressure from the belt driven fuel pump that the engine will try to start? These are electric injectors so they would still open just with less fuel pressure?
I don't want to just unplug distributor as fuel will still be injected into cylinders while cranking.
Any thoughts?

if you want to prelube the engines you either have to pull the dist and prelube or install a prelube system. Doing what you are trying to do is the same as trying to start the engine, not pre lubing.

That is not entirely true. Rotating the engine without starting the engine you are not driving the rods down onto the crank and the crank being driven into the bearings. You are instead statically rotating assembly with no load pressures on bearings.
I didnt want to get into the whole prelube discussion...but...fyi for those who are not familiar: Oil pressure keeps the bearings isolated from crank and rod not oil film. It is not the film that protects although there is a film there all the time or the crank would rust. Those who think synthetic adds start up protection are not entirely correct the only bonus is using a lighter multigrade which builds pressure faster.
Preluber bottles are like emptying your oil filter. After you have pressurized your oil galleries you are now robbing precious pressure to refill the bottle after you start the engine. (think of how long it takes to get pressure after an oil filter change some of these bottles are multiple quarts! There would be a way to restrict refill bottle but won't get into that).
Spinning the engine statically with no load does indeed prelube oil galleries with no load on bearings.

I got long winded and ran out of room! lol
mr3dman you are correct in the fact that loaded surfaces such as cam lobes and to some extent cam bearings will see little benefit from this (quick prelube) however with roller lifters and roller rockers and the relatively low rotation this doesn't concern me. The low end will see benefit from it.
Ever start your engine in spring with no prelube and get slight knock and or tick for a short period? You won't if you minimally use this procedure!
I am NOT advocating this as better than a prelube system, it's not. But it is better than not prelubing low end at all.
Please remember I am not talking about prelubing procedure on a newly assembled engine but one that has crank, bearings and rods broken in.

Why not just start the engines normally at idle rpm like everybody else????? IMO, you are wasting your time. The bottom end/bearings will far outlast the top/valve train. I've never even heard of a crank or rod bearing going bad on a 500efi that was not the result of some other issue.

+1

Why make it complicated? It's not the space shuttle.

i would just start it but if you insist on cranking it first all you need to do is unplug the ignition module so the injectors wont pulse and flood the engine..

It's also a good idea to remove the plugs and then cranking the engine is easier on the starter motor, cranks faster and builds more oil pressure to lube the oil system up. Also gives you a nice chance to check the sparkplug conditiond and clean and gap them if necessary.

Best Regards,
Ray @ Raylar