Ski Boat Oil

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Hi Guys, i have a stock 2002 Corvette LS1 in my ski boat with 460 hours - It's a beast. Since break in it's been ran with M1 15w50. I purchased the boat this spring and left the 15w50 in it since it was fresh, but felt it might be a little too thick of oil to run.

When i changed it this fall, I put in 15w40 dino (per the boat manual) . I actually noticed a slight improvement in acceleration - not sure if it was just in my head. There was no change in oil pressure going from the 15w50 to the 15w40. 35 PSI idle, 50 cruising and 60 wide open.

Anyhow, GM normally specs M1 5w30 for this engine in a car. I know the arguments for thicker oil in a boat due to higher RPM and loads on a boat and higher shear scenarios. But is that old school thinking ? I have read other views that i should be running thinner oil. Some of the newer boat engines are actually running this grade.

Probably just over thinking this but I plan to keep this boat for another 20 years. Thoughts ?
 
If I was going with an xW-40 it would be synthetic (Delvac perhaps), not a conventional. If you only do 30 hours/year (your average), don't beat it hard the entire time and change it every year, the conventional shouldn't be a problem. Nor would M1 5W-30. FWIW, my 2007 5.0L GM Vortec (VolvoPenta) calls for xW-50 if Volvo's "special" synthetic SAE 30 mono is unavailable. I have just put 5W-40 Total Quartz Energy in it for next season as I had enough left over from a stash for a no-longer-owned vehicle. I typically use M1 15W-50 as it is the cheapest. I do about 30 - 40 hours a year as well with a good dose of skiing.
 
The car is different. Note that Vettes often call for a 15w-50 if being tracked. There's still nothing wrong with a higher HTHS oil for a boat. A monograde isn't even out of the question at all, simply because of the usage pattern. You're not using it below freezing, so the need for a monograde is minimised, and fuel economy considerations aren't the same.
 
i actualy put 57 hours on it this year - crazy skier here - I'm gonna put around 60 hours a year.

I was planning to buy M1 5w40 turbo diesel but I ran into a crazy deal on Valvoline Premium Blue 15w40 that I couldn't pass up. 3.50 a gallon - so i bought a bunch.

when I changed the 15w50 at 57 hours it was definitely diluted and dirty so I think I'm going to change the oil every 30-40 hours. Sometimes we pull bare footers at a constant 5000 rpm so that is my only reservation with the 5w30. But then again it's what a corvette would normally run.

seems like 15w40 is the un-disputed holy grail of boat oil from all the boater dudes I talk to, but I like to challenge things. I must admit I'm new to the inboard boat thing - my previous boats had 2 stroke outboards.

Seems like the advantage of the 5w30 would be better cooling ?
 
I don't think you'd notice any significantly better temperatures with a thinner oil. If you were using a 5w-30, I'd hunt for an A3/B4 version first before slipping into ILSAC territory. The usage pattern on the boat will be significantly different than it will be for the average Vette, which probably rarely breaks the double nickel and runs on summer weekends only.
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Look at the philosophy of Honda, who use the same basic engine for their cars and their outboards.

Car might well be specced for 0W20/5W20, but their outboards using the same basic engines call for a 10W30 that meets FC-W.

That spec calls for a post shear HTHS of 3.3

FC-W specs

So Honda are acknowledging that for the duty cycle of the same architecture in a boat, they want something more robust...

So I'd be reticent to run an ILSAC 5W30 in it (2.9-3.1 HTHS BEFORE use)...you could run 5W30/0W30 A3/B4, but they are pricey here.

10W30 FC-W would be OK, but marine oils aren't value for money.

I'd stick to the Premium blue if its there and good price.
 
Originally Posted By: Skier
i actualy put 57 hours on it this year - crazy skier here - I'm gonna put around 60 hours a year.

I was planning to buy M1 5w40 turbo diesel but I ran into a crazy deal on Valvoline Premium Blue 15w40 that I couldn't pass up. 3.50 a gallon - so i bought a bunch.

when I changed the 15w50 at 57 hours it was definitely diluted and dirty so I think I'm going to change the oil every 30-40 hours. Sometimes we pull bare footers at a constant 5000 rpm so that is my only reservation with the 5w30. But then again it's what a corvette would normally run.

seems like 15w40 is the un-disputed holy grail of boat oil from all the boater dudes I talk to, but I like to challenge things. I must admit I'm new to the inboard boat thing - my previous boats had 2 stroke outboards.

Seems like the advantage of the 5w30 would be better cooling ?







You cannot tell if it was diluted unless you do a UOA or there are a few more QTs in the pan than their should be and it's not water.
 
Do NOT run 5W30 or 0W30 in it.

The premium blue you are running is a good oil.

Honestly, Mobil 15W50 is a really good oil and is ideal for your application.
 
The back of my Valvoline bottle says A3/B3-04. That's for the Synpower 5W-40.

I'm wondering if that passes Garak's specifications.
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Originally Posted By: Skier
i actualy put 57 hours on it this year - crazy skier here - I'm gonna put around 60 hours a year. ... Sometimes we pull bare footers at a constant 5000 rpm so that is my only reservation with the 5w30.
...
Seems like the advantage of the 5w30 would be better cooling ?


Sounds like you may be a candidate for M1 V-Twin 20W-50. Stout stuff. Peruse the go-fast, be-loud boat forums and you will hear it mentioned a lot.

Cooling should not be an issue absent some other problem.
 
Do NOT run a 30 in that engine. We're going over a Marine Power 5.3 right now that has a rod knock at 146 hours that's been run on 10/30 RT5.

This is not the first time we have come across a GM engine with early damage from being run on a 30. We still get Volvo Penta engines that suffer damage from people following the obsolete SAE 30 synthetic recommendation on the oil cap.

Seen even more engines with low and inconsistent compression at 400-500 hours using VP SAE 30 and Mercruiser 25/40.

Stay away from the 5/40 HDEO. Most of them shear badly in high performance use in a boat engine.

There's no old school thinking about it. You're fighting fuel dilution, shear, incredible sustained loads, and stratospheric oil temps (even with an oil cooler) all at the same time.

Don't be the guy who trashes his high dollar engine in pursuit of an avantgarde oil solution.

I'm not a huge fan of M1 15/50, but I've backed off of my criticism of it since seeing some very favorable UOA results in engines notorious for tearing oil to pieces.
 
Thanks for all the responses - I'm new around here and I didn't realize there was a boat lube forum
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i guess what I'm hearing is don't run a Xw30 oil and stick with 15w40 or 15w50. The only reason I even questioned what the previous owner ran was the fact that i emailed the engine maker about an unrelated issue and and they said run 5w30 - so i asked why and then they said just stick with the M1 15w50 if PO ran it. Then I look in my manual and it says run 15w40. Talk about a little confusion.

Would there be any reason go back to the Mobil 1 15w50 vs this Valvoline Premium Blue 15w40 ? I have 8 gallons of the PB on the shelf but could sell it easy enough. I did notice the M1 was quieter. But if they are equal quality I will just stick with PB.

I kinda of like the idea of changing the oil more frequently with the cheaper stuff vs just 1x per year.

Shannow - What you are saying about Honda's makes sense - i have Honda Pilot that takes 5w20 and I see what you mean about the heaver oil in the outboards. So I guess that is why they recommended going up to 15w40 in this boat.

Thanks also to DoubleWasp, Garak and others
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Just use a good 15/40 HDEO like you have unless problems start cropping up. You have other maintenance items to worry about with a boat like this, mostly having to do with the cooling system. Since it’s your first inboard (welcome—you’ll never go back) don’t forget to check the alignment, inspect the cutlass bearing for wear and packing gland/stuffing box for the correct amount of seepage, change transmission fluid and fuel filters annually, change the impeller and gasket at the start of each season, clean out your water intake strainers (leave empty after winterizing), transmission cooler strainer, etc. Inspect the manifold/exhaust riser gasket for leaks while running, check out the condition of those iron parts when changing the gaskets or when winterizing. Since inboards take on a little water, as does having wet people constantly boarding the boat, be sure the bilge pump and automatic switch are in good working order.

Do enjoy the simplicity and ease of access that comes with owning a straight inboard! I change my oil every 50 hours or once a year, but my boat splits its duty cycle between pulling skiers and just cruising around a large lake. The old Ford in my Nautique barely dirties up the oil between changes.
 
When it comes to boat engines, I'm a big believer in go big or go home on the lube. Being in the marine repair industry has probably skewed my perspective, but the amount of engines we see worn out with low hours is pretty stupid.

When opened, it's clear that it's due to engine wear and nothing else. For performance V8 boats engines, we've never seen wear related issues with Valvoline VR1 20w50, Amsoil Z-Rod 20w50, or Schaeffer's 20w50. All tend to have significantly cooler oil temps as well.

Unfortunately, we have actually seen a lot of oil pressure issues with M1 15w50 that we've made for away by changing the engine oil to the above 3 lubes. I've been getting the feeling that they may have changed that formula again, because good UOAs are coming out from using that oil.

Compared to the amount of cash spent on gasoline, a premium oil is a cheap investment.
 
Hey DoubleWasp,

Just so I’m understanding you correctly, what are you considering a high performance application?
For example, my 351 is supposed to make 310hp (at least, when it was new) and turns less than 5000 rpm wide open. And of course, ski boats don’t weigh that much.

I’m assuming you’re mostly talking about engines making way more than 1 hp per cubic inch and forced induction engines, in high speed applications (gear cases popping in and out of the water) or big/heavy cruisers that are marginally powered in the first place.

The VR1 20/50 is popular among the rest of the ski boat community (particularly flat-tappet motors) who aren’t otherwise running 15/40 HDEOs or straight weight oils.
 
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