Originally Posted By: Pablo
Why would you change away a proven marine oil?
Please analyze your current oil first. I'm not 100% sure a motorcycle oil is the best choice - ie does it have the best stabilizers, rust inhibitors and FM's for an engine that doesn't change speeds rapidly?
+2 on not changing unless absolutely necessary, but I am by no means an expert. I think OP was looking for a 2nd (backup) option though?
In that case I would say M1 15W50EP would be an acceptable 2nd choice, if in fact it was not the final season end / winterization service. WRT the M1 motorcycle formulation, it would probably be ACCEPTABLE as well, but it would not be my 1st or 2nd choice since it isn’t blended specifically for marine applications.
I think motorcycle and marine engines could both be considered “extreme duty” but are different kettles of fish. Motorcycle and marine engine loadings are different in that motorcycles coast downhill from time to time. Marine engine applications operate under constant load or at idle, essentially climbing a perpetual hill when underway. That is why combustion chamber temps are higher in marine engines vs. other applications, while the overall engine temps are generally higher in non-marine applications than the typical 143-160 thermostats for inboards; not sure about your Merc Verados though. I have read [REF NEEDED] that is due to the thermal precipitation that occurs in salt water at higher temperatures, but that is a different topic and thread.
In any case both engines are “extreme-duty”, but the two different applications operate in very different environments, yield different duty cycles, have different operating rpm ranges, and different power to weight ratios / loadings. So, engine oils blended for marine use should have a slight formulation advantage in marine environments vs. motorcycle, auto, or even some HD diesel oils.
I am not suggesting that you cannot or should not use non-marine oil in a specific situation. However, if you are storing $50K worth of your Brunswick/Mercury stock options for a long northern winter there would be a corrosion inhibition issue with using automotive, motorcycle, or “race” grade oils all blended with fewer detergents for shorter change intervals or for dry environments. Those oil formulations are generally contrary to marine oils and some HD diesel oils that are designed to sit for long periods between use aka to better disperse condensation buildup.
WINGNUT over at the chaparral boats forum posted this insightful nugget of info on the topic at hand:
http://forum.chaparralboats.com/inde...howtopic=13471
BTW, I use the AMSOIL Marine 10W40 w/ a Motorcraft FL-1A or PCM filter for my 18year old MasterCraft with the OE Indmar 351 powerplant with no issues to date.
http://www.youtube.com/watch?v=nPun_jdAjx4
To answer the OP's question though, If I were in a proverbial bind, say on vacation with my boat exceeding the 50hr OIC (not that either of those would ever happen), the M1 15W50EP has enough ZDDP, adequate viscosity, and can be purchased at just about any local auto parts store in the above noted jam, so that is what I would use personally. But then again, oil and filters are like politics and religion.
