Ethanol In Boats – The Silent Killer

I am not a mechanic or a small engine expert but I know my way around an engine and a wrench, or anything mechanical for that matter and rarely end up taking anything to a mechanic or “shop” to be repaired, I can usually figure it out.

I have mentioned a few times that I like to go tarpon fishing in the Florida Keys and a number of years ago when I was in the keys I noticed that all of the gas pumps had “ETHANOL FREE” stickers on them. Honestly, I hadn’t paid much attention or put much thought into it at the time and a few months later I was over at West Boats getting some parts for my Xpress HD22CC and some how the topic of ethanol and boat motors came up. I again, did not pay much attention to it.

Several weeks later another catfish guide that helps me with clients from time to time called me and asked me if I could fish some clients for him, because his boat had broken down, this went on over the course of a week or so while his boat was being repaired with me trying to scramble between my and the other guides at North Texas Catfish Guide Service trying to help keep this guides clients on the water.

Well, this other guide finally got his boat back and learned that ethanol fuel additive was the culprit of the damage of his motor, which finally got my attention so I reached out to a couple of different marine mechanics I know to get the details on what exactly was going on with ethanol and boat motors.

I have two friends right now who are going with the same issues with their motors and again it is due to ethanol in their boats, so I though I would put something on here and hopefully help others avoid the time and frustration (and lost fishing time).

The basic nuts and bolts of how ethanol effects boats (as it has been explained to me) is this.

Ethanol performs fine in most cars and most cars don’t sit for extended periods of time with unused gas in the tank like many boats do.

Boats however (or some boats) sit for extended periods of time with gas in the tank. What happens when the boats sit with this ethanol added gas in the tank is the ethanol sinks to the bottom of the tank. If there is water in the fuel or water vapor (which is a very common problem with boats) the water absorbs the ethanol at the bottom of the tank (where the fuel pickup is for most motors).

Now you have this big mess of water an ethanol at the bottom of your gas tank and you go and crank up your boat motor, which sucks this watery ethanol added mess into your boat motor.

The second problem is that ethanol is a solvent.

Older fuel systems get varnish and other junk into the fuel systems, and then the ethanol gets sucked into the fuel system breaking all that varnish and gunk loose, which in turn causes problems.

The results of both of these issues is generally the same. The motor goes from running fine, to spattering, sputtering, popping and often times the end result is a motor that won’t start or won’t stay running.

This is becoming more and more of a problem, and I spoke to a marine mechanics the other day that said it had increased his repair business in a major way.

The mechanic said that ethanol is the hardest on boat motors in this order:

1. Two Stroke Fuel Injected Outboards

2. Two Stroke Carbureted Outboards

3. Inboard Outboards

4.  4 Stroke Outboards

Way back when I first recognized this was an issue I started asking around on how to prevent these problems with ethanol in boats and the feedback was all the same.

Here is your course of prevention:

First, install a Fuel Filter/Water Separator Kit on your boat between the tank and the engine. Most boats have these built into their engines but they are insufficient.  These are a good idea anyway because again, water in boat gas is a problem and they can save a ton of headaches. If you buy marina gas (which is like playing Russian roulette with your boat motor in many places) these are a MUST have regardless of the ethanol issue.

Second, make sure you change the Filter a couple of times a year.

Finally, make sure you are adding fuel stabilizer every time you fill up. I am using Marine Formula Sta Bil because that was what was recommended  to me across the board by everyone I have spoken with. I was also told that it was very important to make sure that you add the Marine Formula Sta Bil before you fill the boat up with gas and not after.

If you decide not to listen to my warnings, don’t come crying to me when your broken down and shelling out a bunch of cash to fix your boat motor.