synthetic oil in 500EFI?
 

i know this has been written about a lot but, specifically, is there a reason not to run synthetic oil in the 500EFI? They are 2001 engines.
thanks
dan

The only reason I can think of would be if they leak or not. Synthetics will get through that leak much easier, otherwise, no problem using it.

I am under the understanding that the syn oil is to slippery on the rooler lifters and will not allow the roller on the lifter to spin on the can causing cam damage and lifter damage. Also there is the lack of zink in the oil.

Lots of different opinions on that now but that is why I won't run full synthetic in my 525.

I have been running Mobil one or Royal purple in my 500EFI since 2002 not a single problem. Both were in the 20W 50 weights. I have had two diffrent boats. Five, 500EFI's between the two.

No reason at all not to run synthetic oil in a 500EFI.

Thats why you need to use an oil with Zinc in it. It hasn't been removed from all oils. All racing oils are still very fortified with zinc, and so are most diesel oils, non CJ-4.

But why do so many people say otherwise? This is copied from MercuryRacing.comtechquestions:

What type of oil should I use? Can I use synthetic oil?
To help obtain optimum engine performance and to provide maximum protection, we recommend the use of Mercury Precision 4-Cycle 25W-40 Marine Engine Oil. This oil is a special blend of 25-weight and 40-weight oils for marine engines. If not available, a good grade, straight weight, detergent automotive oil of correct viscosity, with an API service rating of SH,CF/CF-2 may be used.

In those areas where Mercury Precision 4-Cycle 25W-40 Marine Engine Oil or a recommended straight weight oil is not available, a multi-viscosity 20W-40 or, as a second but less preferable choice, 20W-50, with API service ratings of SH,CF/CF-2 may be used.

IMPORTANT: The use of non-detergent oils, multi-viscosity oils (other than Quicksilver 25W-40 or a good quality 20W-40 or 20W-50), synthetic oils, low quality oils or oils that contain solid additives are specifically NOT recommended.

The table below is a guide to crankcase oil selection. The oil filter should always be changed with the engine oil.

Air Temperature Oil Type
All Temperatures Mercury Precision 4-Cycle 25W-40 Marine Engine Oil
Below 32? F (0? C) SAE 20W
32-50? F (0-10? C) SAE 30W
Above 50? F (10? C) SAE 40W

This crankcase oil recommendation supersedes all previously printed crankcase oil recommendations for Mercury Racing gasoline engines. The reason for this change is to include the newer engine oils that are now available in the recommendation.

Older owner manuals, service manuals and other publications that are not regularly updated will not be revised to show this latest engine oil recommendation. Current owners manuals, service manuals and other service publications that receive regular updates will receive this revised recommendation the next time they are updated.

IMPORTANT: The use of non-detergent oils, multi-viscosity oils (other than Quicksilver 25W-40 or a good quality 20W-40 or 20W-50), synthetic oils, low quality oils or oils that contain solid additives are specifically NOT recommended.
Come on really? Can this be any more vague, and/or pushing you on the Merc products? A multi viscosity is not recommended except for Merc, or a "high quality" 20-40 or 20-50. Any oil can be used that meets or exceeds their specs, SH, CF/CF-2. And, I believe today, Merc recommends synthetic in their 525's.

Not vague at all. It specifically excludes only "the use of non-detergent oils, multi-viscosity oils (other than Quicksilver 25W-40 or a good quality 20W-40 or 20W-50), synthetic oils, low quality oils or oils that contain solid additives". I do not believe that has changed except in Teague's world since he is now sponsored by Amsoil. The quote that I copied from Mercury's web site is copyrighted 2011. Full synthetic is recommended in Mercruiser production engines only.