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.

Had the boat out yesterday for first run of season. With the 20w50 merc oil it ran 38-40 PSI at WFO. Would Idle cold at 20PSI and after coming down from a lng run it would idle at 12PSI and then climb back up towards 20. I did notice that running wide open for about 3-5 minutes the oil pressure would drop from 38 down to around 35. only ran boat for about 2 hours and no oil consumption. It would use it when it had the Amsoil in it. Just waiting for mech oil guage to double check but I am sure it is just my guage.

How many hours on that 502 ?

240

Seems like low hours for a rebuild. Definitely check your actual pressure, etc....

Now with 25 hours back with the Merc Oil 25w50 it isn't using oil and PSI is now staying just over 40 with the new therostat running 140-150 temp instead of 170.