OIl for marine engines

Amsoil is cheaper than a seatow

Mobil1 15w50 is easy enough to source.

What does the oil temp and pressure gauges look like when running under load?
Temp and pressure are holding fine. I am not worried about an instant catastrophy, but more about the cams long term. As far as expense, well.....
 
Unfortunately none of us PCMO geeks can answer your question. I don't want to be rude but post your question in this forum.
This strictly an engine question, automotive at that. Most people are not going to look in marine forums. These engines could be in anyone's truck, tractor, etc.
 
Flat tappet=high zinc (over 1100 ppm), 10w-40 if you operate in colder weather, hotter weather 20w-50. 15w-40 and 25w-40 are okay also, not sure I would would want a 10W-30, if you get any fuel dilution, it goes thin real fast. Redline, Amsoil, Joe Gibbs have high zinc oil, look through the vigin oil reports and see which oil have the high zinc (high moly would be good too) and choice one of those. Most off the shelf (Walmart, Auto Zone etc) don't carry high zinc oils, they carry SAE oils which have reduced levels safe for catalytic converter and now low calcium safe for DI/turbo engines too. I'm not sure about the levels in HDEO oils.
 
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What type of water and oil temps are you running? While inboard boat engines often have a cooler thermostat than a car does, they lack the air flow around the block/sump that a car has, so the oil temps can be significantly higher. I would chose the weight of oil based on the highest operational oil temperature you see. If you have an oil cooler that keeps the sump temp in the ballpark of ~200f, 10w30 would be fine.
 
I would run this, semi-syn, additives that you want, cost effective and respectable Chevron company, add to that they make many of the private label oils with OEM names on them.
Mystik JT8 15/50 also available in a 40 but in a marine engine I would stick with the 50, The 50 is a CI rated oil the 40 is a CK Marine oil gets hot and the Mystik is not a "heavy" 50
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwj8raeU2YzwAhXCXM0KHdE1BJQQFjAAegQIBBAD&url=https://www.mystiklubes.com/do/product/663004002&usg=AOvVaw3irtcWgoBFyyl5QAfaK1ao

I do run it in my Road King and our small 18' Chapparal not that it means anything to you. I do have many UOAs 5 I think from the motorcycle and 1 VOA posted in BITOG but you would have to go back years looking for it, roughly around 2015

Others have pointed out VR1 which I would agree with, honestly nothing wrong with Merc marine 25/40 more so in a salt environment and last but not least, yeah, Amsoil is certainly a fine oil.
There is one other, dont know much about it but the price is the same as Amsoil - Mobil 1 0/50 racing oil, know nothing about it and rather the VR1 in that case.
 
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I forgot to add. We have a huge percent of people driven by marketing claims here . I'll put a thought in our heads with this question,,, WHAT DO THE COMMERCIAL MARINE OPERATORE USE FOR ENGINE OIL?
 
Quicksilver 25w40 is a Mercury product.
  • For use in all 4-Stroke marine engines – New formula 4-Stroke oils are engineering approved for all marine 4-Stroke applications, including: Outboard, Mercruiser, High Performance, Stern Drive/Inboard, and exceeds all marine industry 4-Stroke oil requirements including FC-W and FC-W Catalyst Compatible.
  • Flagship engine and corrosion protection – Industry leading strength and viscocity retention and ultimate corrosion and wear protection .
  • The most recommended marine oil – Over 5 years of engineering and decelopment by the largest marine engine manufacture in the world.
25W40 recommended in all Marine Engines
 
I know this is an old thread. But how are your 454s holding up?

Marine environments are harsh, lots of WOT and then a lot of sitting. This isn't a 454 in a 1 ton Chevy going down the road.

I run Quicksilver 25w-40 in my inboard 4.3. That thing runs at WOT or close to it much of the time. Someday it'll be at least a 350.
 
what are typical oil temps for a marine engine?
Depends on the engine really. But understanding that marine applications are usually at or near max throttle and RPM 250F isn't uncommon.

Aluminum heads etc, should lower that temp as engine temp is usually quite low due to using seawater cooling.
 
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