Mercruiser oil

[stingray230SX]

now this is a great question/thread cause i recently did my layup and used the standard mercruiser 25w40.
however,i recently switched my truck(1996 toyota landcruiser)to mobil 1 full syn 10w30.
during this time of doing the 454 mag layup i was asking around and of course my local boat shop,where i get everything but the boat(that was a 4 hour drive)says that mercruiser does not recommend any synthetic oils for use in their engines.
the manual does verify this but steps around it by saying no synthetics with solids etc......
i too would like to use the mobil 1 in my engine,but most of the naysayers say if you are changing it every season,then the extra cost of the synthetic is a waste.
incidentally,i use a jabsco sp? hand pump for my oil changes(originally used a cheapo electric but it was slow/leaked at the fittings)now the handpump is super quick,much less messy,i too use a 5 gallon bucket to catch the oil...
doug

[Dr. Eagle]

Like I said in my post above... my old Marlin 21' Daycruiser has around 1200 hours with the OMC King Cobra and I started using Mobil 1 in it the second year I had it. It still has near stock compression on it. And the engine just purrs...That is enough to sell me on it. And my neighbor that bought it loves it and knows it was well cared for.
With synthetic oil, the oil coming out looks better than any petroleum oil, does not have that burnt smell and still feels slick.
There is a noticable difference in the power produced by the engine, albeit not huge.
I find it interesting that after years of insisting on single weight oil, Mercruiser came up with a multi-viscosity oil in a weight that no one else makes. Personally, I think that was designed to create a captive audience...but then I am cynical.

[Miss Rita]

The manual for my 1991 MerCruiser Alpha One recommends Quicksilver 25W-40 oil, but allows 30 or 40 weight oil as an alternative. The multi-weight recommendation is nothing new. Since I never have started my engine when it's cooler than 50 degrees I use 40 weight (Valvoline, if anyone cares!)

[Dr. Eagle]

It was new in 1991. I think it was either 1990 or 1991 that they came out with that oil. Prior to that their manuals specifically excluded the use of multi weight oils as unacceptable for use in their engines.
The 1987 Mercruiser I had recommended Mercruiser 30 or 40 weight oil, or a good quailty SAE Detergent30 or 40 weight oil as a backup.
Regardless the synthetic oil has proven itself to me for my use having used it since 1990. I use it in all of my motor vehicles, except the jet skis...
Actually now that I think about it, I do use synthetic oil in the skis too, Bombardier XPS II Synthentic oil...just not the same oil as I use in the other engines...

[Essex502]

As said...lots of controversy over what to use...I've used Kendall 40wt. Racing per the recommendations of Teague Marine since year one in the motor and synthetic in the outdrive.
Oils in boats are like religion...

[Essex502]

Does anyone (Dr. Eagle) know whether the dipstick on a 502Mag also is the same threaded (3/4" garden hose) connector as the 350?

[Waldo]

I just picked up some Mobil 1 synthetic (15w 50) at Kragen yesterday. They are on sale for 3.99/qt. They also have Castrol Syntec for the same price but not in that weight. You have to ask for a coupon otherwise they won't give it to you at that price.
I too am going to run it in a 350 Mag MPI Merc instead of the regular stuff. First time the motor will see synthetic. The boat is only three years old with 60hrs on it.
Dr, any notice in the running temperature difference with sythetic vs petorleum???
Thanks.

[CV-23]

FYI....The merCruiser 25-40w is a blend of straight weight oils.....Not a multi-vis.....Its not cheap at $10 for 4 qts. I use a Tempo Vaccum Pump to change my oil, Mike.

[cola]

I have talked with Mercury Racing tec's on several occasions with the same response. We only have time to test with our oil,so we recommend it. He adds that there are other oils that comply & are very good, we have never tested with them so no recommendation. I use Mobil 1 in my work trucks, (over 225,000)bike & the 500efi in the boat. I'am on the 5th oil change since April, every 25hrs. I buy it at WalMart in Havasu they always have it in 5 qt. bottles for $ 22.99 I think. Nice bottles to put the old oil in to recycle. The 20/50 V-Tvin Mobil 1 is $ 8.00 a qt. and the oil temp's run cooler then with petroleum base. Works for me.
Later, Mike

[Dr. Eagle]

Originally posted by Waldo
I just picked up some Mobil 1 synthetic (15w 50) at Kragen yesterday. They are on sale for 3.99/qt. They also have Castrol Syntec for the same price but not in that weight. You have to ask for a coupon otherwise they won't give it to you at that price.
I too am going to run it in a 350 Mag MPI Merc instead of the regular stuff. First time the motor will see synthetic. The boat is only three years old with 60hrs on it.
Dr, any notice in the running temperature difference with sythetic vs petorleum???
Thanks.
I don't think I can say I noticed any lower temps in the engine (s), but I do know the oil pressure is more consistent and generally higher after warm up.
That is a pretty good price for the Mobil 1, it is usually a few cents more per quart at Wal Mart.
I did also notice a slight increase in engine performance after going to synthetic, and the oil does not seem to get dirty as quickly.