Too much engine Oil in 2003 Mercury 90 HP 4-stroke

[markriggins]

Hi,

I've seen in the manual and heard several times DO NOT OVERFILL the crankcase with engine oil. Well, the last time I changed the oil, I found it to be a bit overfilled before I began. So I was careful not to overfill it myself. Now, a few months later, I'm trying to get ready for a vacation trip to the FL Keys, and the crankcase is severely overfilled.

1) How can that happen? It's been in the shop once, maybe someone overfilled it, but I seriously doubt it. How can I wind up with MORE OIL than I poured in?

2) What happens when you overfill? How will it affect a running engine?

Mark

 

[gss036]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

What does it smell like? Probably gas, lots of idling at low speeds tend to make oil.

 

[trendsetter240]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

Hi,

I've seen in the manual and heard several times DO NOT OVERFILL the crankcase with engine oil. Well, the last time I changed the oil, I found it to be a bit overfilled before I began. So I was careful not to overfill it myself. Now, a few months later, I'm trying to get ready for a vacation trip to the FL Keys, and the crankcase is severely overfilled.

1) How can that happen? It's been in the shop once, maybe someone overfilled it, but I seriously doubt it. How can I wind up with MORE OIL than I poured in?

2) What happens when you overfill? How will it affect a running engine?

Mark

Hi Mark,

There are only 3 reasons that I can think of for this.

1. Someone over filled the motor with oil.
2. Gas is leaking into the engine internals.
3. Water is leaking into the engine internals.

What does the oil look like? Is it frothy and light brown; would suggest water intrusion.

If it smells like gasoline then it would clearly be gasoline intrusion.

 

[markriggins]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

I'm going to check the oil in the AM (it's too cold outside at this instant), but I'm certain that the oil is not brown and frothy. So it's probably either gas or overfilling. But since this is the second time that the oil volume has increased, then it's probably
gas in the oil.

So what causes gas in the oil? Someone said something about Idling a lot, but honestly we don't do much of that, although we have spent some a lot time trolling, at about 5-10 mph. Is it normal for this to cause gas in the oil?

Does the gas tend to thin and break down the oil?

What happens when the crankcase gets too full. I had seen some periodic smoking, that seemed to occur randomly, and then stop. Now the engine will not run faster than an idle without belching smoke and drinking gas.

Is this from too much oil? Sounds logical to me? I changed the oil about 40 hrs ago, should I change it again or simple drain some? The manual says to change it every 100 hrs and more frequently, with extended trolling, so I guess that that answers one question. But it sure seems early to me.

I plan to change the oil & filter tomorrow, and get the oil level back to normal and see how it affects the engine.

Mark

 

[northernmerc]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

I agree. You definitely should change the oil before running it again.

I once saw a Honda engine damaged by overfilling it. After that, even after lowering the oil level, it never started well and smoked a lot on start up.

 

[rodbolt]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

overpropping,cold running due to defective T stat or a bad fuel pump diaphram will do it rapidly.
remove the fuel pump mounting bolts,swing the fuel pump aside and squeeze the fuel primer bulb. if gas runs out of the pump actuator shaft the diaphram is bad.

 

[markriggins]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

Very useful advice!! I think Rodbolt nailed it. I hadn't mentioned it yet, but when the engine wouldn't run smoothly, the first thing that I thought of was "bad gas" since it has been sitting for a few months. So I pulled the fuel line off the outlet from the fuel tank and dipped it into a quart of fresh gas, and purged the fuel line and filter, and then cranked the engine. I was startled at how quickly the engine drained fuel from that small quart.

Now it all adds up -- if the fuel pump diaphram is torn, it's probably pumping gas into my crankcase. WOW -- sounds like a very bad situation. I'm glad that it happened while we were on land. My sons and I take this boat down to the FL keys, and we've been out 25 miles before on a perfect day. I'd hate for this to happen out there.

I just replaced the waterpump, spark plugs & had the lower unit rebuilt. Plus replaced the steering linkage and entire throttle assembly cables and shift box, live well pump. etc. New radio, GPS, nav lights. We did all this work here at home where mechanics work for a fraction of what they charge in the keys, but it's still pretty expensive.

Salt water is rough on a boat!!!

Obviously, I missed the fuel pump. Is there anything else that I should fix while we're overhauling? I'd much rather have a boat that runs well that we can trust because you never know what the ocean is going to through at you.

This is all on a 17 foot trophy center console, which is almost perfect for the keys, since there's a lot of shallow water, flats, but also a lot of chop and 3-5 foot seas.

Mark

 

[CharlieB]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

Many are lulled into a false sense of security by the purchase of a 4 stroke outboard thinking it to be as reliable as their automobile. Often, they can be, however......

The big difference is the outboard fuel pump is located on and mechanically operated by the engine and not remotely mounted like in our vehicles.

Religiously checking outboard engine oil can often identify a fuel pump problem long before engine damage from thinned oil.

Spare oil, filter, and pump would be wise, but not often needed.

 

[markriggins]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

Is it OK to replace the diaphragm? Or would I be better off just buying a whole new pump?

I'm taking my tool kit with me on my vacation. Everything here in NC is closing down for christmas, so we're going to be in the keys with a boat that has motor problems. Fortunately, they're always open down there for business, except Christmas eve and new years. I can get parts down there too.

Mark

 

[CharlieB]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

Diaphragm replacement should do it.

Rebuild 'kit' including valves (if available) is always the better idea and still a lot less $$ than a new pump assy.

 

[Jeep Man]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

I was reading a very interesting thread a couple of weeks ago about how 4 strokes can have a problem termed "making oil", resulting in an unforeseen rise in the oil level. I couldn't find it through the SEARCH. Perhaps another member could direct you to it.

 

[Jeep Man]

Re: Too much engine Oil in 2003 Mercury 90 HP 4-stroke

Check out a thread from Nov.28 by Bill Jones1234 titled "Gas in Oil 60 HP Bigfoot. You will probably find the post by emckelvy very informative.