Burning motor oil in a 1994 merc sterndrive

zul

Petty Officer 1st Class
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Aug 24, 2015
Messages
235
Sucked out my old oil and put in the new oil and a new oil filter. A few running hours later, the oil level was a quart low. Normal with the new oil filter taking on the oil. Added a quart and had a great trip. Next trip, I noticed the oil go a quart low again. (These Lake Powell trips are 100-150 miles or around 40-50 engine hours.) Added a quart and finished another big outing.

Last trip, I didn't have any motor oil on hand. Stopped into three stores and couldn't get my normal 25w-40 quicksilver/merc sterndrive oil. The sun was setting and we had to drop the boat in to get going. Worried just a bit ... but I had a plan. Lake Powell is a strange and mysterious beast. 42 miles up the lake is Dangling Rope marina. I planned to stop there for gas and some extra motor oil.

Next day, we stop into Dangling Rope and they have a shelf full of all the different motor oils you could imagine. Except mine. *%#$&*. Dip stack says 'Full', so we are ok for now. A barge would arrive in the next day or two and stock up some sterndrive oil. Right. Off we go, fishing, skiing, exploring and camping. FUN!!

Two days later, we pull in for some more of that tasty $4.56 per gallon gasoline. Yummy. And, oh yeah, the oil... Still none on the shelf and I'm 1/2 quart low. Just above the 'Add' line. What to do? I buy a quart of 10w-30, 4-cycle for outboard motors. It was the closest they had. I didn't add it to the engine but I toss it into the boat trunk to have on hand. We've only got 42 miles to go to get off the lake.

Well, at lunch I check the stick. Now we are clearly under the 'Add' line with 20 miles to the boat ramp and the end of the trip. The temp gauge came up a hair and my stress level goes way up. I had to put the quart of 10w-30 in using the "Any oil is better than no oil" idea. Temp gauge returns to its normal position so we cruz straight line and slow to the ramp to get off the lake.

I always watch my bilge water and drain plug water like a hawk for discolor. I always get good clear water coming out, so I feel confident the boat isn't leaking oil off seals or loose filter. But now my oil is less than perfect. The new oil has about 50 engine hours on it and the one quart of 10w-30. SO -- Do I go in and change out all of my motor oil and filter again??? Or can I let it go???

Overall, it looks like the boat is burning one quart every 40-50 engine hours. Is that 'normal burn' or is that 'too much burn' for a 1994 boat?? Total 300 engine hours.

Thanks for the ideas!
 

harleyman1975

Ensign
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May 12, 2003
Messages
959
My chevy truck has burned a qt of oil every 1500 miles since new...its a big block so I think "hey I know its getting oil" a boat is like driving in low gear fully loaded uphill...so yeah your ok using a qt in 40-50 hrs (that is my entire season up here in northern MN). How soon until you change the oil?
 

zul

Petty Officer 1st Class
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Aug 24, 2015
Messages
235
Well, I'm wondering when I should change oil again: Now or next spring? I live in Arizona, so we can boat in Phoenix most of the winter. Problem is the 25w-40 oil is hard to find, even online. I'm only finding the labels that state it's for '4-cycle outboards'. The label on my empty gallon says 'For use in 4-cycle outboards and sterndrives' but I can't find the exact match right now.

I could wait and just run what I've got? But I do need to find a few quarts for adding.
 

Rick Stephens

Admiral
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Aug 13, 2013
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6,118
Switch to a more common oil. I run Valvoline in the boat.... NAPA brand is made by Valvoline. The spec is the same as Gold infused Quicksilver oils. I can't imagine wanting to look for Merc oils.

Sorry I don't have an opinion on the mixed oil... most likely just fine and the base is the same.
 

zul

Petty Officer 1st Class
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Aug 24, 2015
Messages
235
I'm considering a switch to a more common motor oil. Local Wal Mart doesn't carry anything boat specific. I don't mind stock piling the marine stuff but the QS or Merc prices are killing me. Any more suggestions on motor oil alternatives??
 

Watermann

Starmada Splash of the Year 2014
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I'm considering a switch to a more common motor oil. Local Wal Mart doesn't carry anything boat specific. I don't mind stock piling the marine stuff but the QS or Merc prices are killing me. Any more suggestions on motor oil alternatives??

Boats cost lots of money as everyone knows or will soon find out. If cutting a corner to save 5 bucks on an oil change makes that big of a difference then I dunno what to tell you...
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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change the valve seals on the motor

1 quart every 50 hours is not bad. if it was a car that about one quart every 2000 miles
 

JoLin

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Messages
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Agree- one quart every 50 hours isn't bad. I wouldn't do anything about it except carry a couple quarts with me.

Regarding WalMart- they have free 'ship to store' service available on a gazillion items. Have you checked the website to see if you can have it delivered to a local store?

My .02
 

stonyloam

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Oil, a good diesel oil will be fine, I use Rotella 15w 40 in everything, tractors, combine and my Mercruiser. Tractor supply.
 

Rick Stephens

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I don't think you can define what is different about a high end automotive engine oil - like those recommended by GM in an off the line V6 or V8 and a 'marine' oil in the same off the line GM engine. Other than availability, price and label, that is.
 

Scott06

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Apr 20, 2014
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A quart in that many hours is not bad, wouldn't worry about it. In an older 3.0 ran 15 w40 and 20w 50 super tech (aka Walmart $13 gal) no problems. Rotella is equally as inexpensive and does just fine. When I repowered a different boat engine supplier insisted I use Rotella
 

mickyryan

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Apr 18, 2016
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ok just my 4cp"inflation" don't use regular motor oil use quicksilver oil and here is why condensation, the oil will encapsulate water I am told where as regular oil wont because it basically cooks off from higher running temps if your boat runs at 190 or better then you would be fine but most boats never get that hot fresh water cooled anyways.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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FWIW, Ford's threshold for oil consumption is 1 qt every 800 miles. Less miles and there is a problem. More miles and it's "normal". That would be 1 qt in 20 hours.
 

Bondo

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and here is why condensation, the oil will encapsulate water I am told where as regular oil wont because it basically cooks off from higher running temps

Ayuh,.... That is an untruth,....

Yer boat motor oil, regardless the brand, will evaporate the water off at runnin' temps,....
It'll happen quicker at hotter temps, but the process is the same, regardless the brand of oil,....
 

mickyryan

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Hmm id love to read about that because i was told only marine oil was formulated to catch the water
 

JoLin

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Hmm id love to read about that because i was told only marine oil was formulated to catch the water

And I'd love to read about how marine oil 'encapsulates water'. You won't find it cause it ain't true. As Bondo said, condensation in oil evaporates at normal running temp, regardless of whether it's 'marine' or 'landlubber' oil.

My .02
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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marine engine oil is just fancy marketing oil (hint....its a private label branding, just like Cummins oil is valvoline) ..... some marine gear lube does have some friction modifiers in it to allow it to be effective with up to 10% water in it (chocolate pudding) however that is about it.
 
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