Yamaha F115 won't start - 2006

[MNMan2015]

I've had my boat and motor since it was new and have never had any trouble with it until this year. Let me begin with the problem as it has progressed.

Motor wouldnt start on the second trip of the year. It would crank but not fire. After trying to start it over the next 20 minutes, the motor fired. It ran flawlessly the rest of the day. Turning off and starting the motor numerous times.

This past Monday I embarked on a weeklong camping trip in Voyageurs National Park, this was the fourth time it's been run this year. The motor started and ran great on the first day. After being docked overnight, the motor wouldn't start the next morning. I allowed it to sit for a half hour or so again, and it started. I ran it all day, starting and stopping it numerous times. The next morning it again wouldn't start even after allowing it to sit. This time it required a shot of starting fluid into the air intake. I ran it the rest of the day starting and stopping numerous times. The same thing happened the next day, with starting fluid to the rescue. My luck ran out the last day, with nothing working to get it started. My trip came to an early finish, having to be towed out of the park.

As as a note, I only have run non-oxygenated fuel through the motor. I experienced no loss of power or a rough running motor. Only the motor cranking without firing. I am a novice boat mechanic. Any help would be appreciated to get me going again! There is lots of summer left.

[99yam40]

If starting fluid help at 1st then I would be thinking fuel problem, but then when that does not help I would go for spark.
Need to be checking fuel pressures and spark IMHO

[MNMan2015]

Could it be that the low pressure pump could be faulty? It seems like when I would go to start it in the morning there wasn't any fuel present. Almost like it would drain back into the tank. Then after firing with starter fluid, the high pressure pump was able to lift fuel up to the motor. The fuel would stay up in the motor during the day, which explains why it would continue to perform. Perhaps the low pressure pump finally just gave out completely.

Again, I might be dreaming up a fairy tale here. Can anyone confirm if I'm on the right track?

[coueytwo]

First things first. Check spark and compression, if that's good then check fuel.

[99yam40]

Could it be that the low pressure pump could be faulty? It seems like when I would go to start it in the morning there wasn't any fuel present. Almost like it would drain back into the tank. Then after firing with starter fluid, the high pressure pump was able to lift fuel up to the motor. The fuel would stay up in the motor during the day, which explains why it would continue to perform. Perhaps the low pressure pump finally just gave out completely.

Again, I might be dreaming up a fairy tale here. Can anyone confirm if I'm on the right track?

Did you try pumping the primer bulb ?
It will fill the VST

The high pressure pump has to have fuel in the VST to pump fuel.
It will not suck fuel from fuel tank

[MNMan2015]

Another bit of information that I thought of overnight. The boat sat in the garage for a year and a half before I got it in the water this year.

[MNMan2015]

Compression is good on all cyclinders. I found one spark plug was fouled and have new plugs ordered. Would the one plug cause all of the issues? Or just the latest where it won't start even with starting fluid?

[MNMan2015]

Update. I rechecked the plugs. I was mistaken, they all sparked. I reinstalled them, and decided to crank it over. It started. Seems like I have an intermittent problem. Ideas?

[coueytwo]

Next time it will not start, check for spark right then at that time. Check all of your electric connections on the motor and clean all the grounds.

[TownsendsFJR1300]

Drain the VST into a clean container. (I use a tuna fish can). Look for water, debris. Pump the primer bulb until fresh fuel(see below) comes out

Did you put a fuel stabilizer in the fuel for that year and a half?

If not, dump it, its crap.. Fresh fuel makes a BIG DIFFERENCE, especially if there's NO Water in it..

Once running again, start(if not already) using a fuel stabilizer and Yamaha's Ringfree. Excellent product..

https://www.yamahapartsandaccessorie...?b=Search&d=34

[MNMan2015]

I did use a fuel stabilizer. I have burned through the gas that had been in it.

What about my starting battery? I believe it is 4-5 years old. Could it be losing its charge overnight? Explaining why it won't start. Then it charges up full during the day when the motor is being used?

[coueytwo]

Take the battery down and have it checked out. Most auto places will check it out for free.

[TownsendsFJR1300]

I did use a fuel stabilizer. I have burned through the gas that had been in it.

What about my starting battery? I believe it is 4-5 years old. Could it be losing its charge overnight? Explaining why it won't start. Then it charges up full during the day when the motor is being used?

Is the engine cranking over (WHEN COLD) as normal or slow(er)? That has NOT been mentioned previously.

You can have the battery LOAD TESTED for free at most auto parts stores, Walmart, etc. And yes, that's a pretty old battery. Rule that in or out.

If you have a volt meter, the BATTERY fully charged should be about 12.8 volts sitting. Engine running, battery should be showing high 13 volts, low 14 volts(its being charged)...


Re the fuel.. Water settles to the bottom of the fuel tank over time.

Yes, you burned most of your fuel but you also very likely picked up some of that water that's accumulated in the VST/fuel system.

Its ONE SCREW to loosen and drain and check for debris / water. To drain any fuel, debris out of there, might take you 5 minutes. Pump the primer bulb too to flush out the VST..

If you don't/can't do that, well, good luck..


I would check the under cowl fuel filter as well for crap/ water, BASIC maintainance.

I have used this product (K100) since 2007 after I re powered with my F150. I was collecting water in the VST. The boat/fuel tank is 1997 vintage, NEVER DRAINED, PULLED, filter pulled, cleaned, etc.

Between using Non-ethanol fuel and K100, I eventually got ALL the water out W/O pulling the tank, dumping etc. Or at least its mixed and burning off as I run the engine, NOT collecting...

I can drain the VST right now and the fuel looks brand new, smells new, engine runs great and most of the fuel is over a year old(50 or 60 gallon tank-forgot). I buy it by the case...(and no, I don't own stock, but probably should).

Demonstration | Fuel Additive | K-100

Fuel Treatment, Fuel and Gas Additive | K-100 HOME

It does truly work.