Oil for the Mercruiser

Status
Not open for further replies.
Joined
Jun 18, 2011
Messages
75
Location
netherlands
Good day all.

I have a Glasstron powerd by a mercruiser 2.5 120HP @ 4300 RPM.

A perfect running engine, propped correctly.
The duty cycle.

Some plessure trolling, some water skiing, some full throttle cruising.
I change oil and filter every year ( about 50 hours ).
It is used 9-10 months a year temprature varying between 2c and 30c or between 36F and 95F.

The placerd says monograde 30 api se.
Till now i alway's used a hdeo 15w40 ( rated ci4/sl )
Zero oil consumption.
Seems pretty thin whem comming out.
Afther going true some UOA i was stunned by the shearing of multigrades in marine inboard engine's.

Considering going to a monograde.
I have lot's of briggs and stratton OEM oil Available.
It is a monograde 30 rated API SJ/CD.

I cannot find a PDS on this oil so viscosity @ 100c is unknown.
HTHS is unknown

The goal is to achieve long and healty engine life. engine is alway's allouwd to warm up and cool down before and afther hard work.

I guess there is soms fuel dillution going on, as these engine's are know for like the 3.0 140 engine.

How do you guy's think the briggs and stratton oil will hold up?




Is the monograde 30 good enough?

Thank you and please pardon my english.
 
30 weight is fine for that motor, plus no worries about it shearing down. I would think the Briggs oil will work. If I recall it has zinc which is good for you flat tappets.
 
Could always make a short run and have a look at the oil.
Merc sells 25W40 semi synthetic oils to avoid VII and stay in grade
 
When that engine was built;t that was the deal - mono grade. And, in general, mon-grades are the norm for marine applications. But, I might be leery of Briggs oil... The small power equipment 'brand" oils are made under contract to maximize profit for those who think they need to use branded products. And the specific loading of small yard equipment engines is not very high ...

OTOH, the loading on marine engines is very high. There is coasting in a boat engine.

As I recall, that's a little GM Chevy II engine. It's big brother the 2.7 was used in the 140 Mercruisers, and my boat buddy has one. The bigger motor was never offered in cars, only industrial equipment and boats. In any case it's a pretty bullet proof motor
smile.gif


The first thing I'd do is look at the exhaust. I suspect it is running a tad rich. It's common as a starting tune from the MFG to be slightly on the rich side. How do the plugs look? If it's rich, you are getting some slight cylinder wash down and that contributing to the oil thinning. So you want an oil that will stand up to fuel dilution.

Second is the timing curve. It is common, over time, for the distributor to loose the ability to fully advance. The advance plate bushing gets gummy and the vacuum advance does not stroke fully. The centrifugal weights do not fully deploy, and there is usually some excess end play the shaft as they wear, so the ride up the cam gear and run slightly retarded, etc. This does not help with complete combustion so things are cooler than needed in the combustion chamber leaving a bit of unburnt gas behind ...

So I'd go through the distributor at a local shop that still has a distributor machine and an old techie that knows how to use it. It's becoming a lost art, but one worth pursuing in this case. Get it set crack on, or maybe even tweaked a bit for a few more degrees of advance. My bet is you've never heard that motor ping even once on pump regular?

I can't remember what filter fits on that engine... But if it's a spin-on (?), I'd fit an oversized unit. My boat, it'd get Napa Gold/Wix. But you use whatever you are comfortable with. Your local Napa Store can cross reference the current filter to a larger one if possible... More total sump capacity helps with your issues.

Then I'd run Chevron Delo400 SAE 30 in lieu of the Briggs oil. You can mail order it here: https://www.fisheriessupply.com/delo-400-motor-oil-sae-30 if you can't get it locally. It's a pretty stout mono-grade well known in the industry and it usually returns good UOA's.

If you want a synthetic blend, I'd use Chevron Delo400 15W-30 SD (severe duty) which is a very stout GRP III+ and is about as tough as they get.

Baring those two, you are into Motul 300V ester based oil or Redline/Amsoil mono-grades and that's even more expensive. All will service the engine well and and handle the slight fuel dilution very well.

Nice boat and good combo
smile.gif
 
Originally Posted By: Bluestream
30 weight is fine for that motor, plus no worries about it shearing down. I would think the Briggs oil will work. If I recall it has zinc which is good for you flat tappets.


+1 It should be fine. I changed the oil in our families' mercruiser (4.3) with Shell straight 40 and it seemed to like it. I think for a season it should be A OK to use the briggs 30
 
There is no reason B&S would require a high HTHS - what does?:
HDEO - but the wide range vis is packing VII
HDEO mono (Broc L) or 25w40 Merc will minimize loss of grade
 
Mercruiser oil is 25W50 and is a blend without any viscosity modifiers.

Around here people use Shell Rotella T 15W40 and it does not shear too much.

HDEO 30 would also be fine if you run mainly in warm weather.

Lastly most marine engines (pleasure, not commercial) fail due to water ingestion.
 
Originally Posted By: BrocLuno
It's big brother the 2.7 was used in the 140 Mercruisers, and my boat buddy has one. The bigger motor was never offered in cars, only industrial equipment and boats. In any case it's a pretty bullet proof motor
smile.gif



Its was/is a 3.0L engine
 
Have you actually done a UOA for your engine, or are you just reading other people's UOAs?
Until you knew it was causing a problem, I'd continue to run a multigrade, as you're operating in some pretty cold conditions. I'd imagine a straight 30/40 weight at a 2 degree (centigrade) cold start might be more concerning than a 15w40 that sheared/fuel diluted slightly thin over the course of the season. Note that I'm not really basing this opinion on much more than intuition, though...
 
Im not quite sure why you would switch, however it cant harm going with the recommendation of the manufacturer, you do not state the age of the engine.

With that said, keep doing what you are doing. A 15/40 is perfect for your climate.
Why change?

You run the engine in cold weather and the 15 is perfect for that.
You run the engine in warmer weather and the 40 is perfect for that.
You are concerned about shearing, I am not sure why, as the engine calls for a 30, so if it shears according to what you are reading, your down you within engine specs for the oil of around 30..

Basing the Viscosity of oil on what you THINK feels thin while you change it is completely a wrong reason do change what you do.

Me personally? ( i have been boating my whole life too)
I think you are overthinking it and would be a disservice to the engine to go to a mono grade in that cold weather but again, wont harm it if it makes you feel better.
 
Last edited:
The placerd may be old when multiweight oil was not as good as it is today and people ran HDEO 30. But as far back as I can remember Mercruiser oil was 25W50. Today I run Rotella T 15W40 in a Merc 260 which is a GM 5.7L engine with a 4 bolt main and is a rugged engine and GM made millions of them. Taken decent care of and it will run until it injests water.
 
Status
Not open for further replies.
Back
Top