Acceptable percentage of water in gas

[livemusic]

What is the percentage of water in gas that is acceptable for an outboard? Dang, this time it is my 1999 Mercury 150hp on 19ft ProGator and I was going in from fishing, running wide open and suddenly I noticed a def change in sound and reduction in speed. I thought I snagged a fisherman's net or something but after getting to idle and looking, nope. I got going again and it ran 48mph instead of the 53mph it was doing. It sounded rough and I got back to idle. Made it into the dock. It went dead and was hard to crank but I finally got it going and onto the trailer. I am worried that something bad happened. There is oil in the oil reservoir. I checked water content with a little water tester I have and the sample I did is about 6% water. Is this enough to cause a problem?

 

I am concerned because the spark plugs, I see wet oil on the threads and I dunno if that is normal but I don't recall seeing that before.

 

Could a boat going top speed just suddenly ingest a slug of water and run rough? I haven't used the boat much over the past year but I have run it twice in the past two weeks and it was flawless, so, this is surprising to me.

[MN Fisher]

Same as in any internal combustion engine - none. If there's water in your tank, you need to do one of two things.

1: Drain the tank completely, use some sort of water removing system to get the last drops of water out...you want to end up with a tank that's completely bone dry...put in new gas - preferably ethanol free

2: Replace the tank.

[livemusic]

8 minutes ago, MN Fisher said:

Same as in any internal combustion engine - none. If there's water in your tank, you need to do one of two things.

1: Drain the tank completely, use some sort of water removing system to get the last drops of water out...you want to end up with a tank that's completely bone dry...put in new gas - preferably ethanol free

2: Replace the tank.

 

How can I get the tank bone dry, I have wondered about this very thing. I drained it dry as I could get it before I made the first post. I just unhooked the gas line and squeezed the bulb and it siphoned out and I filled up a BUNCH of gas cans. Thank goodness I have so many, lol.

[MN Fisher]

1 minute ago, livemusic said:

 

How can I get the tank bone dry, I have wondered about this very thing. I drained it dry as I could get it before I made the first post. I just unhooked the gas line and squeezed the bulb and it siphoned out and I filled up a BUNCH of gas cans. Thank goodness I have so many, lol.

If you can get access so that you can see the entire interior of the tanks - a quart bottle of isopropyl alcohol in a spray bottle. Rinse the entire interior of the tank, siphon out, then compressed air/time to get the last of the alcohol to evaporate.

 

If you can remove the tank - do so, dump a bottle of iso-alcohol in, swish it around making sure to hit all surfaces, dump it out and dry it as above.

[J Francho]

All my boats have a fuel/water separator filter. I highly recommend it.

[livemusic]

Neither of my boats have a fuel/water separator but I am dang sure going to put one in both.

[J Francho]

They're pretty simple.  Change them every year.  I think they were less $50 a filter.  Well worth it.

[Way2slow]

It sounds to me like you have just discovered what it sounds like when one pops a piston (burnt a hole right through the top of it.  If that is what you heard, to bad you kept running it.   If one is shut down immediately, most of the time it's just a matter of cleaning the aluminum out of the sleeve, honing it a little and sticking another piston in.  However, after you started it back up and drove it to the landing, it probably did far more damage to the cylinder than a simple clean will take care of.

 

So, first thing you need to do is pull the spark plugs and see if one has aluminum in it and look through the hole at the dome of the piston, and see if there's a big hole in it, if it is.  Or just do a compression test, one is probably going to be next to nothing.  If you don't have a compression gauge, just hold a finger over each hole while someone cranks it over, it will blow you finger off the hole on the good ones and may not even feel pressure on the bad one.

Go tell the wife you just spent at least $1,500 and maybe several thousand.  If you can find someone that will fix just that one hole, you might get away with $1,500.  Most just want to stick a remanufactured power head on, that way they don't have to worry about the warranty coming out of their pocket is something goes wrong.

You want to know the sickening part, usually it only cost me about $150 to fix one hole.

[gim]

Just out of curiosity, where would the water come from that ended up in your fuel tank? When I purchase fuel, I expect to get fuel. Not a mixture of water and fuel. It shouldn’t be there to begin with in the first place.

[Way2slow]

Alcohol/methanol/ethanol all hold water.  

Fuel tanks at the stations get condensation, that settles to the bottom of the tanks.

When the tanker trucks deliver fuel, that stirs up everything inside the tank and the alcohol absorbs some of the water.  When you pump the gas into your vehicle/boat or whatever, you can be getting gas with water in it.  Depending on how long after they received a fuel delivery, as to how much water.  It can take a couple of day for it to settle back out.  So, what you are buying for gas, may not be all gas.

[slonezp]

What's an acceptable amount of water in your bourbon?

[E-rude dude]

8 hours ago, Way2slow said:

It sounds to me like you have just discovered what it sounds like when one pops a piston (burnt a hole right through the top of it.  If that is what you heard, to bad you kept running it.   If one is shut down immediately, most of the time it's just a matter of cleaning the aluminum out of the sleeve, honing it a little and sticking another piston in.  However, after you started it back up and drove it to the landing, it probably did far more damage to the cylinder than a simple clean will take care of.

 

So, first thing you need to do is pull the spark plugs and see if one has aluminum in it and look through the hole at the dome of the piston, and see if there's a big hole in it, if it is.  Or just do a compression test, one is probably going to be next to nothing.  If you don't have a compression gauge, just hold a finger over each hole while someone cranks it over, it will blow you finger off the hole on the good ones and may not even feel pressure on the bad one.

Go tell the wife you just spent at least $1,500 and maybe several thousand.  If you can find someone that will fix just that one hole, you might get away with $1,500.  Most just want to stick a remanufactured power head on, that way they don't have to worry about the warranty coming out of their pocket is something goes wrong.

You want to know the sickening part, usually it only cost me about $150 to fix one hole.

I agree this is the exact behavior of a motor that thru a cylinder. First noticeable audible change in motor, actual change in motor power, very difficult to start afterwards.

Mercury is a motor that will still run on a dead cylinder, for awhile, before it totally locks up. 

[BrianMDTX]

I don’t believe anyone mentioned it yet, but the wet oil on the spark plug is telling. Which, considering the other symptoms you described, is likely a definite sign of a holed piston. 

Water in fuel is an issue for any internal combustion engine, from the smallest piston engine on a garden tool up to the largest turbofan engine on a commercial airliner. In fact, aircraft fuel tanks are sumped on a regular basis to check for water in fuel. 
 

Water. Great for drinking. Bad for fuel!

[Way2slow]

How much of last years gas was in the tank.  Old gas will get one a whole lot quicker than water.  

People put too much faith in stabilizers, when they shouldn't be leaving old gas in the tank.

[Ski]

18 hours ago, J Francho said:

All my boats have a fuel/water separator filter. I highly recommend it.

This^

[E-rude dude]

20 minutes ago, Way2slow said:

How much of last years gas was in the tank.  Old gas will get one a whole lot quicker than water.  

People put too much faith in stabilizers, when they shouldn't be leaving old gas in the tank.

Stabilizers only work if you use them for every single time you fill up.

To my knowledge Stabil is the only one without alcohol in it. Something to consider if your forced to use ethanol like I am

[A-Jay]

While we're on the subject of fuel stabilizers - 

This may be applicable & perhaps some food for thought.

A-Jay

 

[E-rude dude]

24 minutes ago, A-Jay said:

While we're on the subject of fuel stabilizers - 

This may be applicable & perhaps some food for thought.

A-Jay

 

I’ve seen arguments for both sides that seemed to make good sense. I can only base my decision to use a stabilizer based on my life experience.

 

For:

2000 Mercury 75 Hp 2 stroke

  blew 3 power heads

  Last one was installed by a Mercury warranty tech. He told me to fill up the tank with Stabil in it to break in the motor. Then bring it back for a carburetor adjustment. That motor is still running today.

 

Against:

2014 Evinrude 115 HO

Used Starbrite Startron in every tank. I switch under a recommendation from the dealer. In the fall I melted a piston completely.

As I normally do I add the stabilizer to my Tundra over the winter since the extreme cold temps up here and my very low miles.

Februaury my Tundra, you guessed it, melted a piston.

 

I have used Stabil ever since with no issues to date. 
 

Anecdotal I know but it works for me.

 

 

[Johnbt]

I've been using Star Tron for 6 years in a Toro zero turn and in a Deere mower on the recommendation of the 3rd-generation lawn care dealer that sold me the Toro. I also use it in a '13 Merc 9.9 4-stroke. It appears to be a simple enzyme with no alcohol in it, but who knows.

 

Stabil worked before that, but I always drained those engines for the winter and I don't drain the riding mowers in order to run them every 2 or 3 weeks during the winter. Also on the advice of the dealer. He doesn't like to see zero turn hydros sitting for months. Or his mechanics don't...  

[Way2slow]

I've probably got a five gallon bucket full of melted piston from over the years.  There's not a one of those I've ever blamed on the gas.  It has always been a screwup of mine.   I will only run top tier gasoline from a high volume station and I only buy what I think I plan to burn.   

[Log Catcher]

For a different twist several years ago I got gas in our car one night. Later on it started running rough. I did manage to get it home okay. I bought some fuel dry and put that in the gas tank to see if that would help it. 

 

The next day I talked to our mechanic at work about it. He seemed to think I got gas with alcohol in it instead of water. The problem cleared up without doing anything else to it.

 

I never bought gas from this station again.

[Alex from GA]

Filled up the boat on the way to Baja many years ago, get there and the boat would hardly run.  Poured some of the gas in a bottle and found a bunch of water.  Luckily I had 2 6 gallon portable tanks and could pour them out easily and get fresh gas.  Had to take the bowls off the carbs and clean the pilot jets to get it to run.  STP gas treatment is a good way to remove a small amount of water from gas without a separator.