Oil recommendation for 4.3 Mercruiser

[ryan c]

hey all,
I’ve recently purchased a 1990 sea ray 180 with 4.3 Mercruiser. It came with all documentation EXCEPT the engine manual. None of the paper work I have on it says what type of oil to use. I’m assuming a good synthetic 20w-50? I’m new to the inboard world. Thanks in advance!

 

[BillK2632]

I have the same engine, I have always used the Quicksilver branded oil (25w40). You can get it at WalMart and is only sightly more expensive than the other brands. I have had several Mercruiser powered boats and always used their oil, no issues. But, oil is a big debate, and many feel that Mercruiser oil is not the best and there are better alternatives. Personally in a 30yr old GM block motor, practically any oil will work just fine - used to be most marine engines called for a straight 30 or 40 weight depending on temperature. We used Valvoline 40 in our Correct Craft - for 2500hrs and it still ran strong, unfortunately quality straight weight oil is hard to find these days. If I were going to use something other than the Quicksilver oil, it would probably be Rotella 15w40. I would avoid a synthetic oil in that engine and stick with a conventional or synthetic blend.

This is from my Mercruiser 4.3 manual:
To help obtain optimum engine performance and to provide maximum protection, we
strongly recommend the use of Quicksilver 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
classification of SH,CF/CF-2, may be used.
In those areas where Quicksilver 4-Cycle 25W-40 Marine Engine Oil or a recommended
straight weight oil are not available, a multiviscosity 20W-40 (SH, CF/CF-2) 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.

 

[Little Ducky]

hey all,
I’ve recently purchased a 1990 sea ray 180 with 4.3 Mercruiser. It came with all documentation EXCEPT the engine manual. None of the paper work I have on it says what type of oil to use. I’m assuming a good synthetic 20w-50? I’m new to the inboard world. Thanks in advance!

To find your manual snag your Serial Number off the engine cover and you can do a search online.

I would stick with the above recommendation Quicksilver 4-Cycle 25W-40.

The Marina and Sea Ray Dealer where my boat was docked most of it's life before I bought it last year used non synthetic quicksilver oil for its standard fill. You may want to call who ever sold you the boat or where they had it serviced to see if they went Synthetic or just standard oil.

 

[paulswagelock]

You will not find SH certified oil at this point in time, that spec is 20 years old.
Any major brand of 15w40 would be perfect. Synthetic not needed.

 

[ryan c]

Thanks everybody! Looks like a walmart stop for quicksilver is in my future.

 

[daniel262]

I use Mobil delvac 15w40 conventional mostly cause I get it for $35 a 5 gal pail (after rebate) and use it in my tractors and F350
If you use synthetic make sure you check it often
Wix makes a nice tall filter too...

 

[BillK2632]

+1 on the tall filter. The block mounted filter for a 4.3 comes in a tall and short version. I get the tall one, usually at NAPA.