Guys I'm looking at a 24 outlaw with a 502. Owner is claiming the block has low oil pressure. I now motors well enough to have rebuilt & swapped 350's etc. Thoughts on why the oil pressure is low? Shot crank/rod/cam bearings? Or something else with a 502 I'm not aware of?

I have seen the built in regulator stick in the oil pump, other than that the usual bearing issues are likely.

according to standard practice here, just put a hi volume, hi pressure oil pump in it and it will be fine...

but back to planet earth... the first thing to do is cut open the oil filter and see whats in it. if its clean and smells ok then i start it for a bit and see what that gage says and then once i had that base line, put a mechanical gage on it and see. if they agree and its low, it could be a dozen things, none of which are any good. price a shortblock and use that plus labor as your guide to what its going to cost to get you going more or less...

I agree with steve about the filter and mechanical gauge. You could also do an oil analysis.

Also, what is considered low? I have read that 10 lbs per 1000 rpm is sufficient.

Sorry, but at this point based on the lack of information on more detailed information on this engine your question really qualifies as a "Dart Board" question. In other words, put the top 25 or so possible reasons the oil pressure may be low on this engine on the dart board and just throw the darts.

If the current oil pressure as being measured has been confirmed with a mechanical guage right on the engine there could be a "low" oil pressure from a incorrect dash guage.
What has the current owner done to confirm the low oil pressure and how low is it and how does the oil pressure act at temperatures and usage?

Based on so called answers to these questions and thoughts I would advise you approach the purchase of the boat as a boat with a possible engine mechanical and internal problem that will require the engine coming out for repairs and possible rebuild based on hours since last overhaul and make your buy offer reflect this requirement.

You could do an oil analysis but that still won't reaaly tell you where the problem if it shows a lot of metal unless the engine is taken apart. A cut open of the oil filter would be another simple test for metal particles and possible internal issues.

"When in Doubt, Check it Out" be careful and protect yourself as a possible buyer.

Best Regards,
Ray @ Raylar

whats low ?? could be anything from the oil, to spun bearing or anything in between...the merc oil cooler/filter system not great either...

If you look up what merc says is min low oil presure on a stock set up, it will scare you. 4 lbs min at idle.
also is it low always or after a run and the oil heats up.

Info I have right now sorry for being vague guys, writing on the fly is helping. 502 gen VI block .030 over aluminum heads. Gaffig digital gauges. Boat runs 35-40 cold idle, 25-30 WOT under load, and the gauge drops to 0 when you idle it after a run. Motor sounds normal.... But my guess is she needs a refresh.

I also am under the impression (not personal experience) that gen 6 blocks burn a bit of oil and run super low pressure. So with a bit more info, Ray and guys in the know... Thoughts? I could also get it with a stock mercy gen 4/5 502 and install it myself but the difference is only 2k realistically

Oil pressure is 40ish cold useless, jumps to 70ish cold
7-10 warm idle, 30-35ish warm WOT
0 hot idle, 25-30 hot WOT
All according to Gaffig digital, haven't convinced him to use a mechanical gauge yet

Price is right though!

Sounds like mains to me. I had a motor eat itself after a rebuild. The gauge showed very similar values. I cut the filter open and it was full of bearing material.
I shut it off when it started falling to 25psi at 4000rpm. I went straight to taking off the filter.
If serious expect a rebuild in the very near future. My experience tells me its not the gauge or an incorrect sender. Could always quick wire a cheap gauge to see what it reads if you think your lucky like that.