I run Mercury Racing Synthetic Blend 25 - 50w in my 525s. Most running is either at idle or cruising around 3500 rpm, and occasionally over 4000. The manual recommends oil & filter changes every 25 hrs. I've read racing oils don't have detergents and need to be changed often, but assume Mercury has blended its oil with the additives to last a season. I run 60 - 70 hrs a season and would like to extend oil change intervals to 2 times a season. My question to you engine & oil gurus is, given the relative mild use, can I extend the oil changes on my 525s to 30 - 35 hrs without risk to the engines?

Maybe it's just me but I never seen a motor hurt by changing the oil to much,,,,,, why push it.

Oil change rules in my world
1. If the interval is say 20 hours it was based on engineering (science) not signs of the zodiac or bumps on someone's head
2. Use the oil (grade) that the manufacturer suggested
3. Don't add any snake oil- wasting money and could compromise the effectiveness of the "designed/specified" oil.-- Sorry if I'm stepping on toes of all the additive proponents.
4. Change the oil filter when you change oil - it's cheap

and

above all If you are conservative -- (this is my philoshpy)

cut the change interval in half

It will NEVER hurt anything changing more often than not!

Just today in "click and clack" a BMW seized- most likely causes - 1. Timing chain, 2 Not changing the oil at the "specified" interval.

3pointstar

ha the bmw interval was 15k miles. Aircraft get changed at 50 hours. These engines run higher rpm extended.... 15-25 hours depending on your level of insanity

Do not extend your oil change intervals.
With the drain tubes on these engines, it's a very simple task, and it's cheap insurance on these expensive engines.

One of the worst things about boat engines is extended down time between outings allowing internals to dry out.
Such is one of the reasons I run Lucas Oil Treatment as well.

BUT, if you want an even better investment, install a pre-lube system that will pre-oil your engines before you start them; AND makes for even easier/quicker oil changes.

IMO for autos more timing chain failures than ever is because the reduce anti wear additives in the current motor oils that is recommended, like Zinc & Phos additive are at all time low blended into the oil . This also relates to using a quality spec motor oil for marine use and or has at least 1300 ppm of zinc and phos along with the proper viscosity.

For a boat engine, a motor oil pre luber is a very good investment. Especially at spring time commission regardless how you do it.

Tell me about high RPM Continental and Lycoming engines. Last I checked 2600 was where about max RPM on our Continentals

I run the same oil as you in my 525's and run the engines basically the same, most of the time between 3500 & 4000 RPM. I change my oil and filters every 25 hours on the button. Better to be safe than sorry, especially when its so easy to do and is the least costly maintenance item on these engines.

I sent samples of my oil to Blackstone labs. I know EXACTLY when to change MY oil. It may be different for climate, usage, oil type, etc. So I will not preach hours, but, if you really want to maximize the oil change interval in your boat. sample and test.

You might be interested in this...

http://www.offshoreonly.com/forums/s...ml#post4331616