Both engines idle rough and then die

[Geiger41]

So is the bad fuel issue the final determination. More reason imo to not top off the tanks at the end of the season. I dont see the need. The gallon or 2 at the bottom of the tank isnt going anywhere whether a full tank or not. the other 45/50 gallons can be put in brand new at the beginning of the season for me. Plus it will be cheaper the first time around bc of filling it up on land. Thoughts ??

 

[tdonoughue]

I have always filled up at the end of the season and store it full in order to minimize the volume of non-gas area in the tank that can be subject to building condensation during temperature fluxuations in a humid environment (like near Houston). At least that was the theory voiced (here I believe?) at one time that made sense to me. I have had no issues.

 

[Scuba_ref]

Stefan, I would also urge you to pull the air cleaners and look for oil on the filters. I think someone mentioned that but not sure if you have had a chance. Over filling the oil will cause some to come back up and soak the filters. It would be odd for that to happen to both engines, however.

I did pull one of the filters as I was going to pull spark plugs to look at and it was clean. The first thing I did on the water was check the oil level on both engines and neither was over full.

 

[Scuba_ref]

So is the bad fuel issue the final determination. More reason imo to not top off the tanks at the end of the season. I dont see the need. The gallon or 2 at the bottom of the tank isnt going anywhere whether a full tank or not. the other 45/50 gallons can be put in brand new at the beginning of the season for me. Plus it will be cheaper the first time around bc of filling it up on land. Thoughts ??

I am going to switch to this method. It will be easier to manage a few gallons of bad fuel than a whole tank full.

 

[Julian]

Are you certain you stored full this winter? Always stored mine full...never had this issue.

Keep us posted on your progress.

 

[tdonoughue]

Actually, if you added 32 gallons after you went out and were unable to keep the engines running, I suspect you did not put it away full. I suspect that you put it away less than half full (with 18 gallons in there), there was condensation in the tank, causing it to become contaminated with water and muck with your sensor (thus showing full).

This is officially my working theory.

 

[Scuba_ref]

Actually, if you added 32 gallons after you went out and were unable to keep the engines running, I suspect you did not put it away full. I suspect that you put it away less than half full (with 18 gallons in there), there was condensation in the tank, causing it to become contaminated with water and muck with your sensor (thus showing full).

This is officially my working theory.

I have been out 4 times this year prior to yesterday's event all on the same tank of gas. So yes it may not have been completely full but it was mostly full. In addition to not being a mechanic, I am also not a petroleum engineer...can gas stratify within the 4ank? Meaning can you run into a bad pocket of gas within the whole body of liquid or is it more uniform? How does the gas interact with water?

 

[Scuba_ref]

Are you certain you stored full this winter? Always stored mine full...never had this issue.

Keep us posted on your progress.

Will do. I'm going to try running it today a bunch to see if I can work some of the through the system in hopes of saving at least one boating day on Monday. We have a new surf board we are hoping to try out.

 

[tdonoughue]

I have been out 4 times this year prior to yesterday's event all on the same tank of gas. So yes it may not have been completely full but it was mostly full. In addition to not being a mechanic, I am also not a petroleum engineer...can gas stratify within the 4ank? Meaning can you run into a bad pocket of gas within the whole body of liquid or is it more uniform? How does the gas interact with water?

You are ruining my working theory. That is not very nice.

I'm not a petroleum engineer either, but I play one on TV (actually, a patent lawyer at an oilfield service company). Gasoline and water will stratify in the tank. However, once you start moving (certainly would happen in 4 runs of the boat), it would start to mix in sort of a messy emulsion (envision when you mix your Italian dressing for your salad). The longer you run, the more it mixes and the more trouble you have. The water has higher density (e.g. is 'heavier') than the gasoline. So in the stratification, the water is on bottom, closer to the intake. So, the purest stuff would be at the top.

All of that having been said, if you filled up with gasoline that had an ethanol content, the alcohol does mix with water (which is why a gin and tonic go so well together--but I digress). And the ethanol will also mix with the gasoline. So this is why mariners dislike ethanol-added gasoline--the ethanol makes it so that the gasoline will 'absorb' water from the high-humidity environment. If you had enough ethanol in your tank, you would not have as much stratification.

So, I still agree you had a bad gas problem. The cause is still a mystery, as my theory is blown.

 

[Scuba_ref]

You are ruining my working theory. That is not very nice.

...

So, I still agree you had a bad gas problem. The cause is still a mystery, as my theory is blown.

My sincerest of apologies on ruining your theory...not my intention at all

I'm headed out now with about 15 gallons of the old gas mixed with 35 gallons of new gas and Heat + Sea Foam for 50 gallons. Hope to burn through a bunch of this and see if we can't get back to normal.

 

[buckbuck]

I predict some 10,000 rpm moments on the lake today. Thanks for keeping us abreast your saga.

 

[Scuba_ref]

@buckbuck your optimism is appreciated. I am currently siting at the very same dock as yesterday where the problem started. The difference between yesterday and today is that yesterday I trailer ed to this dock and today I ran the boat at 10200 rpms for 30 minutes to get here. Looks like everything has worked out.

I was a little nervous when we first put in because the engines didn't want to start. In fact the starboard engine took 5 to 10 minutes to start and then a few more times to catch and stay running. After they were both running it only took a couple of minutes for them to sound like the Champs they are. After that we ran for 10 minutes at no wake near the dock, didn't want to go too far away. Then we blasted up river.

Thanks everyone for your tips, suggestions and moral support.

 

[4x15mph]

How come 4 stroke owners don't use the sierra fuel/water separators in place of just a fuel filter. This is what I use in my 2 stroke and it helps remove any water. Is there a reason this mod isn't done on the newer yanaha's?

 

[biglar155]

@buckbuck your optimism is appreciated. I am currently siting at the very same dock as yesterday where the problem started. The difference between yesterday and today is that yesterday I trailer ed to this dock and today I ran the boat at 10200 rpms for 30 minutes to get here. Looks like everything has worked out.

I was a little nervous when we first put in because the engines didn't want to start. In fact the starboard engine took 5 to 10 minutes to start and then a few more times to catch and stay running. After they were both running it only took a couple of minutes for them to sound like the Champs they are. After that we ran for 10 minutes at no wake near the dock, didn't want to go too far away. Then we blasted up river.

Thanks everyone for your tips, suggestions and moral support.

Sa-Weet!!!

 

[tdonoughue]

How come 4 stroke owners don't use the sierra fuel/water separators in place of just a fuel filter. This is what I use in my 2 stroke and it helps remove any water. Is there a reason this mod isn't done on the newer yanaha's?

I have actually looked at this. However, I don't think my usage pattern or storage pattern will justify the cost and effort to install. It is still on the list; just farther down than a few dozen other items...

 

[buckbuck]

Like tdonoughhue said, I would not be able to justify the cost. All the gas ever put in my boat has had 10% ethanol. I seldom treat it during the season but always do when I tuck it away for winter. I have never had a problem. Perhaps 2 stroke motors are a bit more susceptible to water?

 

[Julian]

Some people have added fuel water separators, but not many (like less than 5 I recall).

Seafoam will help mix the water with fuel and burn it off. You may get a couple more hard starts as the water will still want to pool at the bottom of the tank...but much less so, if at all, dpending on how much you got in there.

Another happy helped member! !!!!!

 

[Geiger41]

Now that were on the topic of gas...I have a half bottle of Yamaha Ring Free leftover from the winter. Once my tank is almost empty and I refill for the first time this summer, should I just use the rest of it?

 

[Evil Sports]

So is the bad fuel issue the final determination. More reason imo to not top off the tanks at the end of the season. I dont see the need. The gallon or 2 at the bottom of the tank isnt going anywhere whether a full tank or not. the other 45/50 gallons can be put in brand new at the beginning of the season for me. Plus it will be cheaper the first time around bc of filling it up on land. Thoughts ??

I have been doing it this way since the 90s without issue. Late in the season I run Stabil in my take each time I add fuel, since I cant be sure when the last day will be I never put more in than 15 gallons at a time after August.
Its rare I have more than 10 gallons on board when I store it. Fist stop next season is the Gas station and so far all is well. It makes me nervous to have 40-50 gallons sitting there for 6 months. Thats a shitload of fuel to deal with if it goes bad and who needs the extra weight all winter

 

[Scuba_ref]

Some people have added fuel water separators, but not many (like less than 5 I recall).

Seafoam will help mix the water with fuel and burn it off. You may get a couple more hard starts as the water will still want to pool at the bottom of the tank...but much less so, if at all, dpending on how much you got in there.

Another happy helped member! !!!!!

@Julian it started right up today and ran great. I think I beat it!

And again, I can't be more impressed with the community spirit on this forum and members' willingness to help each other out even on a holiday weekend. In fact, I was at Home Depot and saw a Yamaha boat parked there behind a tow rig. I sat in my truck and waited until they returned to their vehicle to make sure I had the opportunity to tell them about this site!