I'm planning on rebuilding my 2007 525efi this winter. Not planning on doing much as far as performance mods but one thing I want to change is the oil pump. Not sure about others, but mine has never really produced the pressure l would wlike to see. After running on plane for a half hour or so, it would always be extremely low at idle. Sometimes under 10 psi. I know these are supposed to be high volume and not high pressure but that low pressure makes me really nervous. Is there a better pump option you would recommend?

Mellings, how many hours are on the engine ? you may have other issues under 10 psi not good imo

It is quite possibly a bearing clearance / high oil temp problem and not related to the oil pump at all. I would install a Melling HV pump at rebuild, it is the standard of the industry.

Thanks, I'll get one on order. I got the boat several years ago at 120 hours. I upgraded the valve springs at 200 hours and replaced the stock headers. When I removed the old ones I found they had been repaired/welded. I think the previous owner probably had issues with water as the number 7 and 8 cylinders are 10psi lower on compression than the rest. I was planning to removing the heads and replacing valves as needed but figured if I have it out I might as wee rebuild it. It's got 340 hours now and I average 100+ hours a season if it's running well.

No need to replace the valves unless damaged, have a good machine shop do a valve job should be good to go.

I have a feeling the exhaust valves on 7-8 will be bad. Hopefully they can just be re-ground. Leak down wasn't terrible so it might not be as bad as I think.

After searching around it looks like this low oil pressure while the engine is hot is extremely common. Some say Mercury says 10psi is OK at idle when warm. Not sure why this would be. This is my first 525efi ut I've been building my own performance engines since the late 80s. They always have at least 40psi regardless of temp. The motor has 50psi when I first start it up. 40psi when fully warmed up at idle. If I get up and run for a while and then slow down to an idle, the low pressure light comes on and it's always under 20psi. I've only used Mercury 25/40 oil and Amsoil marine 25/40 in it. Switching brands hasn't made a difference. I'm using the Mercury racing oil filter and change the oil every 20 hours.

Just run a stock oil pump, the big block chev oil system is excellent You can actually run the pan dry with a high volume high pressure. AS stock pump should give you 50 at 5k rpm and 25 to 35 hot idle if everything is correct. By far best bang for buck if you want more power are the heads. You can bolt on 75hp over the factory heads easy. Get a set of afr 315 heads with the Inconel exhaust valve.. If you have questions i have built over 50 bbc engines in many different combos.

How are your oil temps?

Not looking for any more horsepower, just need as much reliability as possible. This is primarily a fishing boat (29' Fountain Sportfish Cruiser) that I regularly take 50-100 miles offshore. Oil temps creep up and hold at 200 degrees if I'm in rough seas and have to stay off plane and run 1400rpm at 7-8mph. Temp drops to around 150 as soon as I plane out. I run two water pickups into a sea strainer. One on the drive and a 1.25" transom mounted unit. I also run the stainless double water pump. Water pressure never drops below 10 psi even at low idle. Oil temperature and headers used to get hot before I installed the dual pump and transom pickup. Oil would hit 220 degrees and headers would get really hot and turn gold. They stay cool now.