# Sporadic VF115 (2015) 184 hours/ Resolved



## Eirus (Dec 15, 2021)

Ive fully rewired the entire ground and power runs from the engine to the battery in the past 10 days. All new wires to replace the 2 AWG and 4 AWG Marine Grade wires on both positive and negative.
I was excited to run the boat I just bought, and finally get over this sporadic when running between 3500 - 4300 rpms issue, only to find my test failed...again. Every time I run it, it consistently runs out of the harbor smooth, but then about 7 minutes later, just drops on its own into a really low rpm, then right back up again on its own...and then back down again. Like its possessed. But at least I know when its coming. I can almost kind of "feel" the engine beginning to start to "stick" or bog down slightly right before the first big sporadic drop happens. Just for a second, it gives me a small bit of reduction, then it starts doing this real sporadic throttling up and down on its own. Ive had a couple of mechanics on board and agree it was electrical. So I replaced those wires, and put solid new lugs on each end.
However, I am beginning to think it could be something else. Even though the last owner swears it is only an electrical issue and that he had a Yamaha Mechanic run tests on the whole fuel system as well as electrical...But why he didn't get it fixed... is concerning.
I don't mind doing this..."long overdue maintenance" I'll call it, of replacing wires and terminal ends. But its demoralizing when it still holds me back from fishing it.
Any ideas would be appreciated.


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## SS06 (Apr 6, 2021)

I had that problem with a Zuk 140 and it turned out to be electrical. Another buddy same motor and symptoms end up being a fuel filter, vst issue. It's very frustrating to deal with


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## Newman (Jan 22, 2018)

@SS06 might be on to something.
Sounds like a fuel starvation issue to me.
Have same power, only issue I’ve ever had was similar and was 100% due to my neglecting to change vst filters after 500hrs.


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## Eirus (Dec 15, 2021)

Newman said:


> @SS06 might be on to something.
> Sounds like a fuel starvation issue to me.
> Have same power, only issue I’ve ever had was similar and was 100% due to my neglecting to change vst filters after 500hrs.


I think you both could be right. I get the feeling when I'm running it that there's some gunk in the filter or fuel system, VST, etc. I wouldn't be surprised either if its bad gas. I should have siphoned out his tank before putting new marina gas in. I'll replace all my fuel filters and VST, and perhaps drain the gas tank, and put new gas in tomorrow and see what happens. I know my power wires were corroded and only hanging on by a thread, so I might have had multiple issues with this motor, which wasn't run hardly at all in 6 years.


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## SS06 (Apr 6, 2021)

I've seen pictures of ethanol fuel that gel'd up into little balls that would roll on and off the screens in vst's and inside filters causing the fluctuations your talking about


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## Eirus (Dec 15, 2021)

Had an interesting turn of events today when I hooked a 3 gallon aux tank up to it to see if it was a fuel line or fuel tank issue. I should mention I also replaced the fuel filter element for $20, but it looked clean, so I dont think that had an effect. But, with the aux tank of 3 gallons of brand new gas, it ran all 3 gallons out of the tank at 4700 rpms. This is a further and higher rpm test run than I have ever been able to do. So tomorrow I will test it again with a 10 gallon aux tank of new gas, and if I can duplicate the results, I know it will be time to siphon out my tank, or check the cap, or the vents, or fuel line for a pinch...


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## Smackdaddy53 (Dec 31, 2012)

Some fuel hoses have a liner and it can collapse under load and you will not be able to see it. This happens a lot in tight bends or places where the hose has been kinked. If you suspect it’s the hose you are better off just replacing it all.


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## topnative2 (Feb 22, 2009)

Are you sure you have enough fuel in the tank?.........boat bounces and sucks air...


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## mwolaver (Feb 6, 2014)

Eirus said:


> Had an interesting turn of events today when I hooked a 3 gallon aux tank up to it to see if it was a fuel line or fuel tank issue. I should mention I also replaced the fuel filter element for $20, but it looked clean, so I dont think that had an effect. But, with the aux tank of 3 gallons of brand new gas, it ran all 3 gallons out of the tank at 4700 rpms. This is a further and higher rpm test run than I have ever been able to do. So tomorrow I will test it again with a 10 gallon aux tank of new gas, and if I can duplicate the results, I know it will be time to siphon out my tank, or check the cap, or the vents, or fuel line for a pinch...


I had a "mystery" fuel issue once. It turned out to be that spin on fuel filter, that wasn't old (according to the date written on it)(new boat). Anyway, in frustration, after trying tons of other things, I replaced that filter and it fixed it. I cut open the old filter and could not identify the flaw. It's always a cheap place to start replacing things...


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## Eirus (Dec 15, 2021)

topnative2 said:


> Are you sure you have enough fuel in the tank?.........boat bounces and sucks air...


New fuel line, water separator, spark plugs and that little filter element did the job. Fixed it. No idea which of those things was the exact issue, maybe a combination of all. But there was gas in it.


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## topnative2 (Feb 22, 2009)

Eirus said:


> New fuel line, water separator, spark plugs and that little filter element did the job. Fixed it. No idea which of those things was the exact issue, maybe a combination of all. But there was gas in it.


I just put on a new racor filter on....weather is crap now......we will see


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## Eirus (Dec 15, 2021)

topnative2 said:


> I just put on a new racor filter on....weather is crap now......we will see


Mine was clear but replaced it anyways, with the fuel line. Ran 65 miles today. I'd say its fixed.


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