your kids show you how to do that ? that's quite amazing and clearly at the limit of your skill set.

the guy that called you tick tack had you pegged perfectly

Do you have oil temp gage?

That's a good idea. You probably will be able to tell just running on the hose with no oil cooler. The oil will warm quickly and the pressure will tell the tale. Check the oil temp with a temp gun on the pan and take your pressure reading when the oil hits 200 although you will be able to determine if there is an issue way before the oil hits 200.

I don't. I need to get one.

I have read over this thread and there is a lot going on.
At this point I would pull the engine and not second guess anything, do this before the parts scatter from the oil pan. No bearing material in the filter doesn't necessarily mean all is well. Bill K , is also correct in saying along with engine bearing clearances in question of having a stuck by-pass on the oil pump. As oil temp goes 180- 220, would not have that much effect on oil pressure. This temp is what I make my dyno pulls at, not that this matters in this situation. The filter being cut open and finding nothing, doesn't mean damage hasn't already been done.
This poor guy, with balancing issues also. I am taking its a 4.250 stroke, 6.385 rod. If he ordered it balanced from Eagle, either internal or external if the incorrect balancer or flywheel was installed it would vibrate the boat or if it was on the dyno, the dyno would dance across the floor. As far, as Mercury goes for balancing WTF how about tungsten.
This all sounds like a serious problem with expensive repairs if let gone. I would try to find someone to tear it down take measurements and locate the problem, before just rebuilding it over again.

exactly

im really hurt now you really need to put the crack pipe down

Update!!! I was reading on another forum where a guy had low oil pressure because his oil hoses into the remote filter were reversed....I never thought about that. When i bought the bought I just took for granted that everything was hooked up correctly...wrong!!! So that means for 2 seasons on the previous motor and 30 hrs on the new motor the oil has been flowing the wrong way through the filter. I guess Im lucky the AC delco filters I have been using don't have drainback valves so the oil could still flow somewhat and be filtered. I hooked them back up right according to the diagram in my merc manual and put another oil filter on there, changed the oil again, and now I get better pressure at higher RPMS, ie I'm always getting at least 10 psi per 1000rpm. However at idle still down near zero on the gauge. A mechanic friend of mine asked me what a manual gauge read at hot idle. I said I only tried the manual gauge at cold idle to compare to the electric, then removed it. He said to put it back on there and see what it reads at hot idle. Ran it across the lake at 3500 rpm several times, never saw less than 10 psi at hot idle the whole day on the manual gauge.

Good news.

Don't mean to burst your bubble dude, but a big block chevy, should not be idling hot under 20-25psi. Even a stock 300HP 454. 10psi in my world would be unacceptable.

My 1989 Chevy 454 Dually, has 135k miles on it, many of them pulling a 5th wheel trailer. On a hot summer day, towing the boat, 190*-210* coolant temps, sitting at a red light, I have 30psi of oil pressure. Thats a factory GM 454, never modified, no aftermarket oil pump, altered bearing clearances, and so on. I'm not running 20w50 racing oil either. In the summer it gets 15w40 rotella oil, because of the flat tappet cam.