CONTINUOUSWAVE

The 2008 Mercury 115-HP FOURSTROKE outboard engine on my Montauk 190 gave me quite a scare. I was ready to come home after a long day at anchor. I started up [the 2008 Mercury 115-HP FOURSTROKE outboard engine ] and let it warm [to operating temperature]. [The engine] started missing, shaking, and finally died. I was able to restart [the engine] but it didn't have enough power to get into gear.

After about eight restarts, the 2008 Mercury 115-HP FOURSTROKE outboard engine smoothed out. I quickly brought [the boat] on plane and got home.

[The cause of the problem] turned out to be the Fuel Supply Module float switch had gone bad. By restarting [the engine] so many times, the fuel lift pump was able to move enough gasoline into the module to get me going. After some research, I found other people that have had the same problem. Apparently Mercury has an improved version of the switch.

When i removed the cowling, I noted that my air filter had also disintegrated, another common problem. I replaced the float switch and air filter in about one-half hour. Very easy motor to work on. [The 2008 Mercury 115-HP FOURSTROKE outboard engine] is running fantastically, again.

If [you have a c.2008 Mercury 115-HP FOURSTROKE outboard engine and it] has the original float switch, you may want to change it before you have a similar scary moment at sea. The [cost of replacement] parts is not too bad, about $85 for the switch.

The rubber seal that goes around the lift pump may need to be replaced. (Mine was disintegrating) That costs another $18.

These problems are probably due to ethanol. I noted that the switch has a seal for its electrical wires and the seal was eaten away. The wires were still good. My guess is that anything is fair game after eight years of use with ethanol-gasoline blended fuels.

I had the same problem [with] a 2013-production-year Mercury 115 EFI. I thought [the cause of the problem] was the pump. No.

I tested the float switch five times; it seemed okay Then I had [the float switch] sitting on my work bench, connected to a Volt-Ohmmeter [for continuity testing]. Without touching [the switch], [the switch circuit] lost continuity.

[With a] new switch installed, [the engine] runs perfectly.

Use of ethanol-gasoline blended fuel has been common in marine fuel for almost 30-years. The federal government recognized use of alcohol-gasoline fuels in c.1987 when it required all rubber fuel hoses for boats to be specifically qualified and marked as alcohol resistant. That was about 29-years ago.

To read that a rubber fuel system component in an outboard engine made in 2008 has failed and the cause is suspected to be intolerance to use of ethanol-gasoline blended fuel is surprising. The cause of the failure should not be blamed on the fuel. Rather, I would blame that failure on poor choice of materials by the manufacturer. It is not a reasonable excuse that the fuel used with the product contained some ethanol. The rubber component in an engine fuel system should have been resistant to ethanol-gasoline blended fuel.

Jim H--I wholeheartedly agree with what you are saying. These components are crucial to the safe operation of the engine and should be designed to live in the fuel that the manufacturer recommends for the life of the engine. So, perhaps I have reached the end of the life of my engine?? I have no idea how long these engines are designed to last. Any thoughts?

Looking at the bright side, these components, (air filter, FSM float switch, and the lift pump rubber seal) lasted eight years and the engine still got me home after a bit of a scare.

Looking at the dark side, had this occurred while I was powering through six-foot waves in the Fire Island Inlet, you might be reading a very different post or no post at all.

In a number of instances of failures of rubber fuel system components of modern outboard engines designed for ethanol-gasoline blended fuels, the presence of excessive ethanol in the fuel being used in the engine has been observed. Apparently retailers are not always dispensing ethanol-gasoline blended fuel with the proper 9:1 ratio of gasoline to ethanol. Some boaters have purchased their own ethanol fuel percentage test devices and routinely test the fuel they are getting for proper ratio. An alternative solution is to avoid as much as possible the use of any ethanol-gasoline blended fuel.

In Michigan, there has been state legislation that requires fuel wholesalers to make available non-ethanol fuel specifically for marine fuel dock retailers to provide for boaters. This has resulted in very widely available pure gasoline, no ethanol, 90-Octane fuel, generally sold under the branding of REC-90 at on-the-water fuel docks and marinas.

It has also become possible, although in Michigan it is certainly not common, to find highway fuel retailers that offer a similar fuel, often under the branding of PREMIUM 91-Octane no-ethanol fuel. The availability of non-ethanol fuel seems to vary by state. In Wisconsin I have found that non-ethanol fuel is quite prevalent at highway fuel retailers. In Michigan, to find highway fuel with no ethanol requires a careful search and selection of fuel retailers, but it can be done.

For more about a simple and inexpensive ethanol fuel test device, see

Ethanol Fuel Testing
Determining ethanol content in blended gasoline fuels
http://continuouswave.com/whaler/refere ... lTest.html