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Michael T

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nhsd

You just bought a new boat expensive enough that it has twin 350's, don't cheap out on the oil. Follow the specs and use the full synth oil. Just my opinion and spending your money, not mine... $-)

Michael T

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Babyboomer

If you don't go by the book and something happens that book will hit you in the ars!
I don't have a c converter and have used Mercury Synthetic Blend for years and am very happy with it.

Michael T

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Michael T

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Dream_Inn

Yep, once Al commented I was right there as well!

Funny oil story...I was so used to buying regular for my 310, when I bought the 400 last year, I put like 5 quarts in and then looked at the manual figuring out how much the thing holds (dumb move, I know - should've read first).  Well, I had to remove that oil and put in the synthetic and it took like 8 quarts each engine!

212rowboat

Dream_Inn said:

Yep, once Al commented I was right there as well!

Funny oil story...I was so used to buying regular for my 310, when I bought the 400 last year, I put like 5 quarts in and then looked at the manual figuring out how much the thing holds (dumb move, I know - should've read first).  Well, I had to remove that oil and put in the synthetic and it took like 8 quarts each engine!

Just be happy those aren't oil burners.. that would have been about 15 quarts each instead of eight each!! :-)

Have you guys ever heard of "cajun crust"? ... It's the only drawback to using syn that I've encountered... If you've ever pulled an intake manifold off of a wedge engine that has ran primarily syn oil, you've seen it... It is a hard straight black crust that loves to coat lifter retainers (spiders), and any other non moving parts.. syn clings to surfaces much better than dyno oil, and when oil stops flowing, and rests on those hot parts, it bakes on tougher than blueing on a firearm.. it's generally not a problem, but it can theoretically create tolerance issues for tightly mapped engines.... The tighter the tolerances, the worse the impact (which is to say the better the build the tighter the tolerances).. but even so, the detergent and suspension properties of synthetic over dyno can't be denied, and the cajun crust thing can be greatly reduced by simply allowing the engine to cool down before killing it... Or, maybe even better, installing an electric aux pump to allow oil flow through the engines under its own power instead of the mechanical pump the engine relies on for a good ten minutes after killing a warm engine...

Don't get me wrong, it would take like thousands of hours for that crust to form, but these things aren't nearly as easy to build as a car engine, and getting to those mechanical pumps, bearing caps, things like that, are mucho harder..

Black_Diamond

I deal with high end / high power gearbox manufactures and gas turbine people. All will tell you synthetics far out perform regular mineral based oil stocks. We are talking equipment that can run 24/7/365 and costs hundreds of thousands of dollars running multithousand HP. Look up the temperature capability for both. Not even close for the same VI index.

Prelubers are used on expensive diesels, but they do nothing to cool oil unless you have some externally powered oil cooler.

212rowboat

Like I said, the only negative is that cajun crust stuff..

the circulator isn't so much for cooling as it is to keep the suspended ash from cooking on hard parts after the engine stops circulating of its own volition.... Call it a rinse, if you would..

Speaking from a builders perspective, though, one thing to concern about is an abrupt shift from dyno to syn.. it's rec'd, and understandably so that a person should change to syn, then change again in a few hundred miles or a few hours operation.. the thing that happens is that the better detergents and the suspending properties of syn loosen sediment dyno has left behind, which like to head directly to the little trashcans of the block (the hydraulic lifters).. oops.. a collapsed lifter can easily happen when debris block the port/passage..

Many of the better builders I know rec you either always run dyno and stick with it, or do the same with syn.. syn being the better choice... From my own experiences though, I've learned that either is great, so long as it is replaced at the proper interval... The enemy of modern oil isn't that it loses its lubrication properties but that it suspends all the crap it possibly can, and debris don't lubricate..

Capt_Steve

This is INCREDIBLE information...thanks guys!

Michael T

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212rowboat

The 'looser' specs are a bit of a misnomer.. they are channeled. The channels allow critters such as cranks to float on bearings instead of come into actual contact.. here is more engineering in that, though, than simply leaving them loose.. they have to be capable of loading and exchanging the oil.. we're talking about a pretty dang small 'gap', though.. and we're talking about a design that will charge/load the 'gap' almost within a revolution or two.. which is why it's a pretty decent notion to allow an engine to idle to temp than it is to turn the key and break plane as soon as you can, just because you can..

Damage and wear happens to engines when they start, if all other systems are working properly and healthy..

But back to oil..

Everyone I know swears on Amsoil.. they love it because of the long intervals they can get between changes, and its proven lasting qualities.. problem: lasting lubrication properties isn't the issue with modern oil, dyno or synthetic.. suspended ash is the problem, which places the blame of failure on filtration, or lack of maintenance/replacement... For the point of engine ownership, the most important thing you can do is swap oil on a rigid schedule.. I HIGHLY recommend Blackstone laboratories for oil analysis at least every other oil change.. there is no better way to know what your engine is experiencing for the $25 it takes to get that analysis.. google those fellas.. I use them religiously for all my more expensive toys..

212rowboat

I attached an oil report from Blackstone-labs to give you folks an idea of what to expect if you ever choose to go that route..

there is, in my opinion, no better way to manage an expensive engine... Again, marine engines are hard to get to when it comes to doing simple things to them we take for granted with a stand mounted engine, or one in a vehicle.. You can't just drop the pan and get a peek at the bearing caps, or pull the screen on the pumps pick-up tube, ect... Unless you pull the engine.. If you go that far, you likely already have issues... If you used a lab report on the oil- you maybe could have headed it off at the pass, so to speak...

If you write Blackstone an email requesting a sample kit, they will send you one for free... all you do is fill it according to the instructions and send it back w/ a $25 check, or you can pre-pay w/ a cc... the $$$$ it can save you in the long run can't be ignored. 

MarkB

I'm confused. Mercruiser specs SAE 25W-40 oil in the manual, black bottle. This is not a fully synthetic oil, or so I've been told. I think it is straight grade oil.

The Mercruiser 20W-40 oil is fully synthetic, comes in a red bottle. Haven't seen this readily available.

Are you guys really using the 20W-40?

Babyboomer

The Red Bottle I use is Synthetic Blend both bottles are redish in color looks purple here but it's more red watch your labels pictures of both below.

seguir

Fully synthetic wasn't available at our marina.....they are recommending the blended Merc SAE 25W-40.  Which is next in line in the manual.   Your thoughts?

TikiHut2

Drew, Awesome info. Thanks for adding your engine experience to the forum and welcome aboard. I'm due for an oil change in my boat so I'll send in a sample to see what they have to say. 

As for changing from traditional to synth, I recently switched oil types in my 100k mi SUV from Castrol oil to Mobile one synth after lifter noise prompted me to drop the oil pan and see what was in there. Even with 5k mi oil changes It was so full of sludge that the oil pickup was almost completely clogged causing low oil pressure to the knocking  lifters. I cleaned the pan and swapped to syn (lifters stopped rattling instantly)  and re-checked it after 200mi and just like you mentioned it had quickly dislodged a substantial amount of internal crap. Just re-changed it with a new filter and will watch it closely. Yikes.

And for everyone else, I'd also wonder about intervals between oil changes for the boat. My '04 350 merc had just been serviced when we bought her last May and now has about 45hrs on the last oil change. It would seem a bit premature but maybe it should be a seasonal change instead of dependent on minimal hours of use (within reason of course)? Any insight?

Mike

212rowboat

thanks, Mike... I think I'll like it here to be sure!!

Seguir: for what it's worth, in my humble opinion, you can simply use what you have available that is within specs- 5w isn't that big a difference, especially when jumping the gap between full syn and a blend.. the absolute key to it all is monitoring it, and then replacing it when it's past it's prime..

Dream_Inn

What about this stuff?

 

Babyboomer

Same stuff I see that black bottle a lot where they sell & service outboards

TikiHut2

Great detailed info in a timely post since I'm also due for an oil change.

 

So MichaelT, as you started the post by saying you intend to use "fully" synthetic 20-40wt oil, have you found it somewhere that we might shop? Aside from the one pic that Boomer posted of a red bottle above showing "fully synth" oil everything else clearly says blended. He has a great point to carefully read the label so you're not paying premium dollar for a blended grade.

And to follow that, while I appreciate the loyalty to Merc brand names, has anyone seen a more readily available and compatible "fully synthetic" oil that'd spec to the same wt and quality? 

Michael T

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MarkB

I assume for my 20 hour service I should stick with the normal 25w-40 to help break in the engine? When should I change to fully synthetic?

Michael T

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MarkB

OK thanks MT. I'm at about 18 hours. So by next week I'm doing the 20h service. Will go with fully syntehtic unless someone thinks it wont help the rings to get seated properly.

Michael T

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mvn

Well,  thanks to all of you I just realized I've been using regular Dino oil for the last 2 years.   I guess when I'm paying 12 bucks a litre,  I assumed it was synthetic!   What a dummy! 

Off to the store now........ 

Mark

212rowboat

there isnt anything wrong with modern ancient lizard oil... :-) 

its just not as good as synthetic... it is still a lot better than it was even ten years ago... so long as you changed it regularly, your engine is still happy.. 

Michael T

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MarkB

Doing the 20 h  service today. Going to top up with fully synthetic  mercruiser oil. Thanks for the heads up.