Mercury 25hp PCMO

Joined
Dec 11, 2019
Messages
4
Location
Whitby, Ontario, Canada
Hi,

I own a four stroke 2007/2008 Mercury EFI outboard. I know FC-W oils have been discussed extensively here, but in owning my motor I have only used supertech conventional 5w30 or 10w30 oil. I use the motor in Canadian freshwater only. But here is the interesting part: I only use the motor 15-25 hours per season (across all engine speeds, general use) and change the oil and gear lube annually. Would using PCMO really be all that detrimental to the motor with such a short oil change interval?
I have had no problems with this motor (actually a Tohatsu) and it purrs like a kitten on start up. It is my belief that the oil I have used, probably at an HTHS of 3.0 cannot be all that worse at 25 hours of use than an FC-W approved oil at 100 hours. Thoughts/ideas are welcomed! Thank you.
 
Outboards have another factor not as big a problem as in cars. This is possible corrosion from being put away wet, even fresh water the exhaust is wet when put away. If you have iron or steel liners, they can rust. I think the FC oil has more corrosion inhibitors.

Rod
 
Thanks for the response, Rod. My boat is stored in an arid place during the winter but during the summer months just sits on my boat lift between uses (like most cottage boats). I'm wondering if a passenger car motor oil can handle the continual 3000+ rpm of cruising speed for up to 25 hours in the summer. So far, so good, but I wonder about the shearing with this oil at higher revs. I have no problem switching to marine oil, but it is a curious idea. I think boat motors manufactured during this time straddled the launch of NMMA FC-W oils and the same model engine (but a few years earlier) would have only required an API SJ or later oil.
I have never seen a cylinder liner/sleeve corrode before.
 
I use HDEO in 10W-30 in a 115 Yamaha with no trouble. Thought it might hold up a little better, but maybe not.
 
Originally Posted by SimpleGuy48
Thanks for the response, Rod. My boat is stored in an arid place during the winter but during the summer months just sits on my boat lift between uses (like most cottage boats). I'm wondering if a passenger car motor oil can handle the continual 3000+ rpm of cruising speed for up to 25 hours in the summer. So far, so good, but I wonder about the shearing with this oil at higher revs. I have no problem switching to marine oil, but it is a curious idea. I think boat motors manufactured during this time straddled the launch of NMMA FC-W oils and the same model engine (but a few years earlier) would have only required an API SJ or later oil.
I have never seen a cylinder liner/sleeve corrode before.


Living in Whitby I can guarantee your storage space, unless heated and the humidity is controlled, is not arid. It may be dry if indoors but as you know or ought to know, humidity in our neck of the woods is nothing like being way up north or in Arizona.

I'm not telling you what engine oil to use, that is your choice, but believing you will never have moisture issues is incorrect thinking.

Also curious about your 3000 rpm statement? Just wondering if that is where you run it constantly or do you open it occasionally? Not sure the size of your outboard, but I am going to guess 6000 +/- RPM's is likely it max range. It is important in an outboard to run to that max rpm occasionally. Lugging an outboard and not running it through the rpm range occasionally is very hard on them.
 
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What's the price difference between QuickSilver/ Mercury oil vs a PCMO? I would use the correct stuff.
 
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