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115 Four Stroke Going after the V S T Filter

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LakeRat1

Member
Hi You'll back a couple week ago I was intouch with a couple of you Guys about my fuel problem, and it was decided that most likely problem was a pluged VST Filter, I have now pull the rig from the water, armed myself with a Seloc Repair Manual, and also down loaded some parts Diagams, I have a couple Questions before I order my parts that I am sure one of you can answer for me, 1st= The VST filter is inside the VST Assembley, & under the high Pressure Pump (Right ?) do I replace this filter or can it be cleaned?
Next thing, there is a inline filter just after the fuel leaves the low pressure pump, dont I need to change this while I am after anything that might be causing my motor to bog down under a load above 2000, but will REV to 4 or more out of Gear
I had been in touch Docksidemarineservices & DWard, but help fom any of you Good Helpers will be Great, This old man can do it Just need a Couple Good Coaches!!!!! Thanks a Bunch

LakeRat1 will be standing BY

 
I havent seen what was said on a previous topic, but have you checked the fuel pressure, especially when the problem is happening...
Also, have you done a drop test to make sure all cylinders are firing??
 
I replaced the VST filters with new ones........but when I was cleaning my injectors in my ultrasonic cleaner I threw the old dirty VST filters in and after 10 minutes they came out looking like new. If you don't have an ultrasonic cleaner I'd order a new one as you don't want to get it apart and then have to wait. The VST filter attaches to the bottom of the high pressure pump in the VST bowl.

On my 115s I didn't change the cartridge filters between the low pressure pump and the VST as they weren't plugged.....I just blew some air backwards through them. I guess I'd inspect them and if they don't look bad I'd clean them. Those are pretty big filters compared to the small filter area on the VST filter.

Did you ever have any luck getting the attachment that lets you hook your pressure gauge up to the VST?
 
Thanks for Your Replys, First to answer tonyaus Replys, I have changed my add on NAPA 12 Micron water seperator, as well as a inline filter after that and before the fuel gets to the motor, when i changed the spin on water seperator filter i dumped it and there was no trash of water, i had added a double dose od marine sta bel to the fresh fuel, motor does not miss like a plug problem, it will rev as hig as i dare try when out of gear, get under way, runs fine at 1000, and fine for a time at 2, but get on it and before it gets to 3 it will bog down, slow down and it will recover, and as long as you dont push it to hard runs fine, but keep giving it trottel and at some point it runs out of gas,

DWard i was never able to locate a cross over from the Standard Schrader connection on my furl gauge to the Small Schrader connection on the Fuel Rail of my motor, i would still love to fine on, but i went ahead and pull the rig out of the water while i had help, i tried Snap On and a number of other Tool Companys, i may need to try a Yamaha Dealer, the one in this part of the Country don want any one to be able to do their own work, if you know where i can get a crossover like i need please let me know, i plan to order all my parts on line before i tare into it so once i open it up i can replace the filters and o rings and what not and close it back up,
DWard do i have to drop that lower motor clowing in order to get the intake manifold out?

Thanks Again
LakeRat1
 
Below is my post from your previous thread. There is a link to a couple pictures showing the engine before and after the manifold is removed........you don't need to remove the lower cowling and the intake can be leaned out instead of completely removing it.

You're on the right track. The pump on the back is a diaphram pump that feeds the VST. The bowl and filter on the back has a red disc inside to tell you if there is water in the gas....the red disc will rise up in water and stay at the bottom if no water there. The cartridge filter is to filter between the mechanical pump and VST.

To replace the VST I first removed the plastic air intake from the intake manifold. There are about 2 or 3 bolts that go through the manifold into the block, and about 6 that bolt to the intake itself. You'll need a ujoint and extension to get the bottom bolt. The intake itself has a couple bolts on the intake side and about 5 that bolt it to the block. There are 3 bolts that hold the VST to the intake (mine had yellow paint on them) and I'd wait unitl the intake is loose and leaning out before removing those. There is a metal gasket between the intake and block that you need to remove and keep track of which end is up and down as the bolts don't line up if it's not on correctly.

Once the intake is leaning out, there is a fuel line on the bottom of the VST that is a return from the fuel regulator and the intake fuel line that I removed from the VST. I left the high pressure line to the fuel rail on the VST and removed it from the bottom of the fuel rail. There are also a few vacuum lines that need to be removed from the VST. You'll need a 3/8 drive 10mm, 12mm abd 13mm socket with a 6"extension and a ujoint as the bottom bolt on the plastic intake is down in there. Once the VST is out a phillips screw driver gets the bowl off and then you'll see the VST filter which you replace.

As for the injectors they are a lot easier to get to and may or may not be plugged. It's about $20-$25 each to have them serviced........you decide whether you want to service them now or later. The fuel pressure reading would help you in figuring whether they are plugged up or not. I'd guess that once the VST filter is clean and changed things will run a lot better. I did a lot of research and figured out how to clean my own injectors, but it takes an ultra sonic cleaner and an aparatus to push cleaning fluid through the injectors. I did this because the boat is in Florida and I was on a tight schedule.......if I had the boat around I probably would have had the injectors cleaned by someone like injectorman.com or others I heard about on this site.

Below is a link to a picture of before and after intake is removed. When I changed mine I didn't take the intake completely off, I leaned it out. I also googled "change yamaha f115 vst" and found a bunch of information that helped, and you'll probably find something that I didn't see.

http://www.thehulltruth.com/boating-forum/297623-yamaha-f115-vst-filter-change-w-question.html...-question.html
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Last edited by dward; 06-27-2011 at 04:29 PM.​
 
Its unfortunate that you cant read your fuel pressure, cause I think this reading will just about point to your problem.
Another thing to look for, would be the little filters that are on each injector, or for the $100 to service/clean them, it may be worth doing regardless...
Another thing you could check, is the inlet needle on the VST. With the VST cover removed, you can even put a hose on the inlet side with a primer bulb attached, and when the float is hanging make sure you have a good flow when you are pushing fuel through it...
As far as that gasket goes, I dont think you really need to replace it, but for about 10 bucks, i wouldnt chance it...
 
Thanks <> tonyaus<> for your Reply, I will send my injectors out to be cleaned, as for cleaning the Fuel Rail, do i need to send it off alonf with the Injectors, or is that something i can do with some type strong cleaner, Thanks Again

LakeRat1
 
My 115s have probably had the intakes off and back on while servicing the VST about 4 times and we haven't replaced the gaskets yet. Although I always thought it wouldn't be a bad idea to have a gasket available just in case.

The fuel rail shouldn't need cleaning unless something has really gunked it up but you definitely don't need to send it off.

As for the injectors, it wouldn't be a bad idea to have them serviced, although I'm guessing they aren't the problem. I cleaned all of mine and like tonyaus mentioned the little filters in the injectors are usually the problem if they act up. The little filters in the injectors are actually pretty easy to replace. Below is a link showing a diy cleaning on some ford injectors where he shows how to replace the filters in the injectors. The yamaha injectors are similar but don't need any of the pintle cap parts as they only have the orings on top and bottom and the little filter baskets.

I got the baskets and orings for my injectors from fuelinjectorconnection.com I think the baskets were 50 cents each.


http://www.rowand.net/Shop/Tech/DIYFuelInjectorCleaning.htm
 
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