Being that it's fuel injected and well taken care of, I agree that having a used oil analysis is the best possible way to get a feel for proper interval. If not you are simply draining it too soon or leaving it in too long. There are studies that do show very short internals can cause more wear, so saying draining oil too soon has zero negative potential is false.

Also, just because the Mercury oil says "racing" that does not equate to little to no detergents in the oil. If you ran a true straight weight race oil without detergent, at 25hrs you'd pull the plug and be lucky to have some thick good drip out. For Mercury they set the internal and spec said oil, and they know that a true racing oil which won't have any detergents would likely be a legal nightmare. So it's just advertising.

Can you point to some of the studies.

Change the oil at 25 hours nuff said!

Thanks for your input. My past experience with Mercury oil has been very positive. I had a 454 Mag MPI owned since new and used only Mercury 25w - 40 oil, rebuilt at 900+ hrs. Its internals were clean and in great shape, only really needing head work. I ran it another 400 hrs before selling the boat and it was still running strong. It was interesting that Mercury recommended oil changes every 100 hrs on this 454. I changed it every 50 - 60 hrs because I thought this was too long an interval and it was thick and black when I pumped it out. Also the 454 would burn a quart every 25 hrs.

I've now had the 525 for just over a year and been changing the oil every 25 hrs, and it is relatively clean (compared with the 454) when drained. Also the 525s do not appear to burn any oil between changes, the level remains constant on the dip stick, never had to add oil between changes, and I check it very time before heading out. If I were running hard in poker runs every weekend I could see the reason for the 25 hr change interval, but with recreational cruising the hrs add up fast. I have no issue changing every 25 hrs and will continue doing so, but was wondering if it was over kill in my situation.

Thanks again. This forum is a great place to share and learn from each other. Have a great boating season.

Good convo here for me, first time 525 owner I too boat very lightly, dont "poker run" my engines (high rpm) and was thinking of extending interval times. Not anymore after reading these posts. 28hrs since last change, so I guess its time.

Question re removing the oil filter. Do you just poke the top to drain to reduce the mess? What is that allen head plug for right where the filter screws on? Is that a drian plug for the upside down filter?

Only OEM oil and filter anything engine for me....

i would also like to see the study that said changing oil to often causes more wear,i never heard of that and will say i can,t believe that is true information.please post a link to this study.

Oh man. You do realize you're getting into an oil debate with Borgies BFF dont you?

Another oil discussion? Say it ain't so! Lol. You can do a general search about oil and you'll find numerous threads on this with varying opinions. On a 525 it's best to just follow OEM guidelines.

To set the record straight Merc recommends oil changes for the HP 525 every 25 hours or 30 days which ever comes first. And that 30 days even includes if the engine has only 1 hour of run time on it.

With that said whoever said changing your engine oil too much causes extra wear, I guess you need to call Merc and tell them all about it.

I never put new oil in my boat engines. I run the oil in my work beater car for at least 500 miles, then drain it out and pour into my boat engines. Its like break in for the oil.

Fresh oil is hard on parts.