VST Filter FYI...

[smann316]

I have an '01 F115 that was loosing power. I spoke with a mechanic and he told me that more than likely it was the VST filter. I got home removed the VST and visually inspected it. There was no visible debris and it looked clean, I could see through it. I re-installed it and ordered a new LP fuel pump, fuel/water filter, in-line filter and sent the injectors off to be cleaned. Got everything back together with high hopes. Put her in the water, gave full throttle and nothing had changed. I was pulling my hair out. Out of my own options, I took it to a factory trained Yamaha mechanic and he got the fuel guages (which I do not own) and it showed 20 psi, which is about half of what it should be. I told him the same thing I just wrote and he asked me about my VST inspection "did you blow through it"? I said "no, I didn't know to blow through it". He said that the ethanol in the gas can form a clear film over the VST filter and over time cover it so the fuel pressure is too low for the engine to function properly. SOOOOOO he is gonna replace my VST filter for me and pray that it is not the HP fuel pump. There are 2 morals to this story. 1. Get fuel guages and check fuel pressure (it will save lots of time and $$)! 2. If you don't have fuel guage and don't want to purchase one, blow through the VST filter as part of your inspection.

I hope this tidbit of info is helpful.

[BaileysBoat]

Let us know how it ends up.

[Sparkieboat]

fuel gauges are cheap enough on e-bay..

[Blue197320]

my new vst filter was put in 3 days ago and it has a film on it already. my mechanic looked at it today since im having an issue with my ox66. what does your mechanic say to do about the ethanol? besides run recreational fuel.

[tonynorie]

fuel gauges are cheap enough on e-bay..

Please tell me just what I should search for on Ebay to get the correct gauge. I'm assuming you're referring to a fuel PRESSURE gauge? Is it just Yamaha Outboard Fuel Pressure Gauge or something more specific? Many thanks~

[smann316]

Well, in my life nothing can be as simple as a VST filter replacement. Turns out there is a hole in the cylinder head cover that is causing my problems. A $150 job just turned into a $600+ job. It's good to be me!

[99yam40]

I do not understand how a hole on head cover would cause this problem.
Maybe I have already had too many cool ones this evening.
Was it a hole in head? or the cover?

[smann316]

He said it was the valve cover. I have just spoke on the phone with the mechanic about it. He is a Yamaha "Master Technician", which is why I went there. I'm a little confused and he said if we did not repair this then I'd be spewing oil everywhere. I am interested to see what he is describing to me, because right now I am in the dark. I just hope I don't have to pull my pants down when I pick it up tomorrow. We'll see. I will keep you in the loop.

[99yam40]

Please let us know when you find out, because I am not sure of how a hole in valve cover would cause loss of power. I do understand about it spitting oil every where with a hole.

Did he say how the hole happened?corrosion?

[smann316]

He said that someone in the past who worked on it left testing clamps
Or something like that on there and they were corroded really bad. I will know much more tomorrow.

[Sparkieboat]

I got one of the cheapest fuel gauge kits I could find, it came with a few adapters and fit the top of my fuel rail. I cannot remember exactly which one, but I think any of them would work. local auto parts store should have one also

[smann316]

Whew!!!! There's good news and bad new, for me that is. The good news is my boat is running like a champ! The bad news is it cost me $571!! Ok so here's the deal. The mechanic got the fuel pressure back and fired the engine and could tell it was not running right. He got his laptop and diagnosed a bad pulser coil. As he was accessing the spark plugs to test them and the coil he found a test harness used in testing the coils. Apparently the test harness had been in there for over 2 years. The mechanic that worked on it the last time when going over the engine for me prior to me purchasing it, apparently left his test harness connected and that's what the second coil was running off of. It now makes sense, why as I was running WOT and all of a sudden it lost power. The wire on the test harness corroded through and came apart, so i immediatly lost 2 cylinders and no matter how many filters and fuel injectors I got cleaned, I wasn't getting those 2 cylinders back. Thank goodness for Yamaha Master Mechanics and laptops. I'm sure it saved me some labor and maybe un-needed parts. Luckily the pulser coil was fine and just needed to be plugged back in. So you ask, why $571? Well as they were removing the cylinder head cover a screw was corroded and broke the cover when they got it loose. Bad luck on my part. anyway, we are repaired and me and the family are going for a ride tomorrow.

[rodbolt17]

most likly the cover broke when someone smacked the screw with an impact driver.
I have seen that twice.
will poke a nice round hole,typically in the lower stbd side.
when the cover screws are stuck I drill off the head.
thats also why I have a Kv tester to check secondary firing voltage without removing anything but the hood.
that engine will run on one pulser coil.
will idle fast and top speed cannot be reached but it will run.

[smann316]

That's exactly how the cover broke. Anyway, ran it today for several hours pulling the kids on the tube and ran WOT for a while and it did great. The only thing I noticed, was at the end of the day it was idling very fast znd the shifter was kind of stiff going into neutral. Other than that it worked perfectly.

[rodbolt17]

are you nuts?
its EFI.
if it idles fast and is hard to shift to N, its BROKE.