Oil recommendation

[Bad Habit]

Does anyone use or recommend synthetic oil in a 1987 350 mercruiser? I've been using a straight 30W for years but wondering if there would be a benefit to using a synthetic. If so should I stick to mercruiser oil or could I use Mobil 1?

Thanks Rick

[Ontario Obsession]

for some reason I decieded to go that route this year same motor  cant see where it could hurt, going to run her tomorrow I,ll let you know how it works out.

 

[borderline 350]

Dear Bad Habit,

                       I use Mobil One (5W30) in my 2011 GM car because the engine & cat. converter will only OPERATE correctly and the engine internal parts have been updated to ACCEPT LUBRICANTS WITHOUT A ZINC ADDITIVE.

....I do not recommend the use of any synthetic oil in marine engines, especially the engines that are used for TROLLING at low speed for extended time periods. BECAUSE THEY DO NOT CONTAIN a zinc additive. This additive is especially needed in all the older marine engines with flat face hyd. lifters. The EPA required the oil mfgs to remove the this additive around 2000.(TO PROTECT THE CAT. CONVERTORS) Since then, a lot of work in the laboratory and with the camshaft mfgs. has revealed PREMATURE camshaft & lifter failures due to this ZDP additive being removed!! Go to "Speed Talk" and read the several years of ZDP problems. The only oil mfg. making an excellent product with high ZDP is BradPenn. in Bradford, Pa. Their label has a warning about use in engines cat. converters. DON'T!! The old time good oils like "Kendall" are now made in South Korea & packaged in California..................X-Jet Boat Bill

[Bad Habit]

Thanks for the replays. I think I'll stick to the oil I've been using and never had a problem ( If it ain't broke don't fix it)

Rick

[Misty IV]

I considered going to a synthetic a few years ago in my 4.3 MerCruiser, but didn't for many reasons, some of which Borderline mentioned. I've stuck with the MerCruiser 25W-40 without any issues. I agree with the "if it ain't broke, don't fix it" theory.

[Chas0218]

Does anyone use or recommend synthetic oil in a 1987 350 mercruiser? I've been using a straight 30W for years but wondering if there would be a benefit to using a synthetic. If so should I stick to mercruiser oil or could I use Mobil 1?

Thanks Rick

That year motor should be fine running either oil.  

 

The issue is when you get pre 1986 with the non roller cam shafts.  Without the regular motor oil and high zinc additive you will wear the lobes off the cam. 

[borderline 350]

Dear Chas 0218,

                           PASSENGER car engines 4.3, 5.0, 5.7 built by GM  did start using roller hyd. lifters in 1987 ACTUALLY after Jan 1st, 1986 "2nd Design".. As far as my experience repairing the GM  "Marine Engines" used by Merc/OMC/Volvo, ONLY flat face hyd lifters have ever come out of the OEM marine engines built all the way into 1997. The latest one I did was a circa 1997 5.7 "Mercruiser Magnum" high performance VORTEC "880" block and that had flat face hyd. lifters. So beware of what the Boat People tell you. My experience/knowledge is based upon actual disassembly of these engines.

........................X-Jet Boat Bill

[Adk1]

I have an older 1991 4.3L Mercruiser carburated in my islander. will be my first year changing the oil. What should I run for oil weight in her?

[borderline 350]

Dear ADK1,

                    Mercruiser recommends their 25W40 oil I believe. This is an excellent product in my opinion. Engines used for long duration trolling applications could use straight wt. 30 or 40. And change it at 60 hour intervals also!.................X-Jet Boat Bill

[Adk1]

Well that is good because that is what I bought