I have a 2002 volvo-penta DPX package in my boat, that uses a 502, similar to a mercruiser 502mag motor. It runs great, but seems to be using way to much oil. 130 hours on it, original motor never been apart. Runs 25-40 mercruiser oil. I put 2 hours of extended rpm run time on it (4200+rpm) across havasu, up river, then back down again later in the day, and maybee 40 minutes of idling in and out of no wake zones / coves......and it used almost a full quart of oil. There were maybe a total of 15 minutes total of 5000rpm operation here and there @ redline. Is this excessive oil use for a 502? I've heard these motors use a poorly designed oil ring, similar to the GM factory 502 crate motors, and they will "use" oil. Opinions?