i am finding that i'm using oil, in my 36 outlaw with 502mags running 24 pitch 4 blade pros. could using these props cause the use of oil' also not finding any oil in bilge or on the outside of boat. any help????????

502's use lots of oil. Normally around a quart every 10-15 hours. If you are not seeing it in the bilge then it is most likely normal.

From what I am told it is normal for the 502 to use some oil, I was told it is due to the tolerances for the forged pistons? Not sure how correct this is.. I have a 99 502 mpi that came in my boat when I ordered it new, and it does use about the amount that Knockld said.

As mentioned above the 502 Mag does use oil. I have been down that road and there is probably nothing wrong with your motors, it is just the loose tolerances they are built with and you get a lot of blow by until the engine is up to full operating temp..

Two things I found that will help you to use less oil.

1) Which to a straight 40 weight oil. The Valoline racing oil is a great product.

2) Do NOT run your engine above 3000 to 3500 RPm until you get good oil temp.

Once the engine is at full operating temperature the pistons and rings have expanded and there is less blow by.

The 502 Mag is a great engine.

Enjoy

what is a good operating temp on the oil? straight 40 won't be to thick? thanks for all the help.

220 Degrees F or less

No it is not too thick. Merc actually recommended the 40 Wt on my 502 Mag. If I did not like and have such good results with the Mobile 1 15W50 Syn in my 500 EFI's I would be running the straight 40 weight. But my 500's do not have the blow by problem that the 502 Mags do.

You are welcome.

Happy Boating

I use straight 40 weight in my boat, thats what the dealer and Merc recommends. I always have good oil pressure and very little oil use.

Sept. 07 PowerBoat mag page 27, Teague touches slightly on this subject.

should i change oil out, or start adding 40 weight as i start needing oil?

Last boat had 502 mags....added a qt every 10-15 hrs. Do not add a different type of oil, just wait and switch at the next oil change. I like the Mobile1 15-50 and the Vavloline straight 40 weight. I've used both and either would be fine in your motor, just personal preference.