How much Oil?
 

How much Oil does a 502 in a 25 Ol (1999 Fuel Injected)take. Just changing the oil for the first time since I have owned it. Also, it uses oil. Seems every day out it needs a litre of Oil. Boat runs strong, Oil pressure is only 35 at WFO and about 8 at idle after a good run and will climb to just over 10 at idle. Still will show just over 70 on speedo and run 5000 with a 23 M+ prop.

7 qts. I think I would start saveing money for a new motor!http://www.perfprotech.com/store/App...l-capacity.pdf

We had a 25 with a 502. Ours used oil as well (502's are known for that). I would be more concerned with the oil pressure. What type of oil are you using?

Time for a rebuild. You should have no less than 20 psi after a hard run and you should be around 50-60 psi at wide open at top rpm.

I'd verify your sending unit is not bad or your gauge with a mechanical, but if you only have 10psi of oil pressure it's time for rebuild.

Yes, gonna check with a mechanical guage 1st. The guy who had the boat before me ran amsoil 10w40. I just switched out to 20w40 merc Oil and used the K&N long oil filter. Where is the sending unit located on the 502?

Down by the filter pad adapter.

I had one that dropped like yours, ( actually to 0 ),,,,got lucky and ended up being the sending unit.

Hope you are as lucky !!!!!

I had a bum sending unit that was causing faulting readings, and would fluctuate sometimes. I would verify with a oil pressure gauge before you worry about a new motor.

Rule of thumb is 10psi for every 1000rpm of engine speed. At least 10-15psi at idle, generally it is higher than that though.

And what oil are you using? You should be running a thicker oil such as 20w50, not traditional car oil such as 5w/10w-30/40

20w50 in it now with a K&N filter

You should be running 50-60lbs of oil pressure while underway.