Outboard motor oil

Oct 24, 2010
2,405
Hunter 30 Everett, WA
Not me. Consumer Reports did a massive test of oils in NY cab engines. It was a well done test that involved tearing down the engines and micrometer on the parts before and after an abusive test. Bottom line: it didn't matter which oil you used, change it on time. The problem is with contaminates.

Ken
 
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Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
Different brands are also a consideration when selecting the oil to use. While in college I took a class in materials and the best tests for me related to oils as I was actively flat track motorcycle racing and a tuner/builder of such bikes. The variances were amazing to behold as different brands had distinctly different reactions when subjected to heat and flow tests. When oil started smoking, when it flashed, flow rates at these different temps. etc.. Valvolene and Castrol rated the highest with Pennzoil last of about 12 brands. Be aware that these tests were done in 1980 and probably not true today. I do use the top 2 brands to this day. I have never used special marine 4 stroke oils for marine use but I of course use special 2 stroke oils. I do not recall using a special marine 2 stroke oil either. I was a top tuner/builder and Yamaha Dealer. Chief
 
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Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Do y'all use synthetic oil in your 4 stroke outboards?
My tohatsu service manual specifically says no synthetic motor oil. Change out the oil every 50 hours OR end of season, whichever comes first.
 
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Mar 26, 2011
3,401
Corsair F-24 MK I Deale, MD
Pretty funny, considering most oils contain synthetics as vis correction fluids these days. Just sayin'.

I also found it strange no one mentioned meeting FC-W specs, as laid out by NMMA.

Because motorcycles run hotter, comparisons to outboards are generally false. In fact, the oils for 2-stroke bikes and 2-stroke outboards are covered by different specifications for this reason. They are not closely related.
 
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Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
Yes Thinwater they are closely related. Motorcycle racing motors stress the oils much more than an outboard does. I don't think I made comparisons between outboard and motorcycle engines but you can rest assured that the stress level is much higher in motorcycle engines! (both 2 & 4 stroke) I have used and worked on outboard engines just as long as I have worked on motorcycle engines and that is a long time! Chief (small engine certified)
PS: What may be overlooked here is the fact that virtually all sizes of motorcycle engines have been water cooled for many years.
 
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Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
I googled small engine certification and you CAN get separate small engine certificates now based on different uses. The full coverage certificate for small engine is still offered to cover ALL small engines as well. Complete small engine certifications is offered by state junior colleges which is where mine comes from. Chief
 
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Mar 26, 2011
3,401
Corsair F-24 MK I Deale, MD
Yes Thinwater they are closely related. Motorcycle racing motors stress the oils much more than an outboard does. I don't think I made comparisons between outboard and motorcycle engines but you can rest assured that the stress level is much higher in motorcycle engines! (both 2 & 4 stroke) I have used and worked on outboard engines just as long as I have worked on motorcycle engines and that is a long time! Chief (small engine certified)
PS: What may be overlooked here is the fact that virtually all sizes of motorcycle engines have been water cooled for many years.
Again, yes and no. Air cooled engines run at higher temperatures and thus use different additives. Corrosion issues are different. I respect your maintenance experience, but I used to work on the oil formulation side. They are both difficult applications, but they are slightly different. TC-W3 was developed because some air-cooled 2-stroke oils were causing plug fouling and ring sticking. Lower temperature and fixed RPM were considered to be factors. Thus TC-W# oils, for example, are ashless.

Bikes are formulated to TC, of which TC-W3 is a subset. The truth is that most good oils will work fine, and that not all brands go to the trouble of even trying to meet marine standards for a tiny market.

There are also different specs for 4-strokes (auto an marine). Again, many good oils have never tried to certify in this tiny market. I've long used non-FC-W oils, but I sure wouldn't give that as advice. So long as we are discussing this, and if people want the whole story, 4-strokes should meet FC-W. Go to the NMMA site and read up. The specs are there.
 

capta

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Jun 4, 2009
4,766
Pearson 530 Admiralty Bay, Bequia SVG
My Johnson's manual specifically states that synthetic oil must be used in that engine. Even if I wanted to change, I've heard this is a very bad idea, though I don't know why. Stick with one or the other.
 
Nov 26, 2012
2,315
Catalina 250 Bodega Bay CA
Other than Evinrude there are few 2 strokes being made anymore for marine use. There are few 2 stroke motorcycles made anymore either even though a 2 stroke can still outrun a 4 stroke flat track or motocross racer. Chief