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Gringo all I can say is what a great read.........
No nothing at all about your motor,but reading the whole thread it sounds like you said before 2 seperate issues, water one you have fixed, now it's a fuel problem.To me it seems as somewhere there is a restriction in the fuel system that is allowing your initial burst of 5000+ rpm,but once that bit of fuel that is past the restrication is comsumed it can no longer supply the amount of fuel to continue running at that level. I know this is of no help to you but mate keeping going you will sort it soon..
Best of luck..
The little screen filter on the bottom of the VST pump is ten micron. The Plastic filter I took of is 28 micron. Since the fuel is going through a ten micron Racor before it even gets to the motor, the Yamaha twenty eight micron was not doing anything. Plus it was causing problems, swelling up. Probably due to the ethanol in the fuel. The thing was a pain in the posterior, anyhow. I kept it, if I ever need to reinstall it. But I am thinking more along the lines of putting another Racor or other 3 or 5 micron after the present Racor ten micron.
Plan tomorrow is to run out (weather permitting) and try squirting fuel in the air intakes again. But this time while running wide open.
I hear all that but old Yahmaha had a lot of dirt it the fuel filter on the engine after the Recor filter, moral of the story, leave the filters in place.
No, you misunderstand. The Racor just went on in the last couple of weeks. Before that it was an old Perko. What dirt there was on the VST ( the first 10 micron in the system, before) made it through the Perko and the 28 micron Yamaha filter. There was not a lot of dirt in the fuel filter on the engine. Nor was there any water in it. The Perko caught the water. But that plastic filter was a pain. It is distorted and leaking.
Why would I want to leave it on? it's not only useless, it's causing problems. Kind of like a broken, infected tooth.
The fuel gets filtered to ten microns by the Racor. It would be kinda useless to put even a good, functioning, 28 micron filter after that. It's like filtering something through cheesecloth, and then filtering it again through burlap. What's the point?
Add to the fact that the burlap is contributing to the problem. Get rid of it.
There is no "story". And therefore, no "moral" to it. Simple engineering.
Well, this thing is trying to drive me nuts. And it's getting pretty good at it. Yesterday took the two boost pumps off to check them. Procedure is to squeeze fuel bulb and see if fuel comes out of the hole on the back of the pumps. They seal against the crankcase and operate by vaccum. Well, the boost pumps didn't leak, but fuel gushed out from around the o-ring on the Yamaha onboard fuel filter. After checking with the Yamaha Guru, we discovered that this filter is 28 microns. I also discovered that you should be able to tighten the ring on it all the way so that very few threads are showing. This is as far as I could tighten it:
So, since it's between two ten micron filters...and obviously warped or something, and leaking air into the fuel system, it's essentially not doing anything useful. I took it out.
Thats much simpler, don't you think? I doubt any 28 micron boulders are getting past the Racor, so who needs this there to leak?
Thinking that an air leak in the fuel system at this filter could have been causing the other issue, we filled up our five gallon tank with fresh gasoline and launched the boat again. No change. It runs up to about 5100 or so RPM for a little while ( less than a minute, something like fifteen seconds) and then gets ragged and RPM drops off to something around 3,000. And it won't go back up to 5,000 again. Until the next day.
We dumped four oz of Sea Foam in the four gallons of gas we had left, and ran around til that was just about gone. Then we tried to make another WOT run. No change.
This is making me start to research sailboats.
First off good luck getting the issue resolved, you have certainly spent plenty of restless hours on this motor. I had the same issue with the bowl that you took off. I do realize that the filter is not as fine as the others but that bowl is there to allow any additional water that gets through the filters to settle and it will allow you to see if you are getting water in the fuel. There are def to many threads showing. Here is how I fixed mine: After changing the filter, I noticed that when I squeezed my primer bulb, fuel would run down the sides of the bowl. I simply took some fine sand paper (I think 600 grit) and worked it around the lip that is on that bowl. You will sand it until it will fit all the way onto the O ring and screw completely on. It doesnt take a whole lot of sanding, for whatever reason the fuel causes that bowl to swell. I hope this helps. At least when this is over you will know an HPDI in and out OR take up sailing! Good Luck
No, you misunderstand. The Racor just went on in the last couple of weeks. Before that it was an old Perko. What dirt there was on the VST ( the first 10 micron in the system, before) made it through the Perko and the 28 micron Yamaha filter. There was not a lot of dirt in the fuel filter on the engine. Nor was there any water in it. The Perko caught the water. But that plastic filter was a pain. It is distorted and leaking.
Why would I want to leave it on? it's not only useless, it's causing problems. Kind of like a broken, infected tooth.
The fuel gets filtered to ten microns by the Racor. It would be kinda useless to put even a good, functioning, 28 micron filter after that. It's like filtering something through cheesecloth, and then filtering it again through burlap. What's the point?
Add to the fact that the burlap is contributing to the problem. Get rid of it.
There is no "story". And therefore, no "moral" to it. Simple engineering.
My point is that dirt & water got pass the racor that the engine filter caught.
My point is that dirt & water got pass the racor that the engine filter caught.
No, you missed that part. There was no dirt or water on the engine filter. The stuff on the VST filter was most lkely aluminum oxide from the inside of the VST tank. There was no debris there. Just a thin, almost uniform coating of this silvery stuff.
But even if there HAD been dirt and water in the yamaha engine filter, it would have been dirt and water that got past the old Perko filter. Not the Racor. I replaced the Perko filter with the Racor during this whole thing.
The Perko is sitting on my workbench. i am thinking I will make a bong out of it.
First off good luck getting the issue resolved, you have certainly spent plenty of restless hours on this motor. I had the same issue with the bowl that you took off. I do realize that the filter is not as fine as the others but that bowl is there to allow any additional water that gets through the filters to settle and it will allow you to see if you are getting water in the fuel. There are def to many threads showing. Here is how I fixed mine: After changing the filter, I noticed that when I squeezed my primer bulb, fuel would run down the sides of the bowl. I simply took some fine sand paper (I think 600 grit) and worked it around the lip that is on that bowl. You will sand it until it will fit all the way onto the O ring and screw completely on. It doesnt take a whole lot of sanding, for whatever reason the fuel causes that bowl to swell. I hope this helps. At least when this is over you will know an HPDI in and out OR take up sailing! Good Luck
What the yam mechanics do is rotate those bowls. When they change that filter for you the bowl that gets put back on your motor was from the engine that they service before you. Once that bowl sits for a while it shrinks to size. You can very easily do the same by purchasing a new bowl and do the rotation yourself.
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nah, Yamaha actually has some good mechanics here. All their expertise is focused on their commercial outboard customers. There are around 100 small fishing boat customers with 85's etc. on Provo, and another 50 that get supported out of Grand Turk. NONE of those are HPDI's. So Yamaha here has no training, experience, or parts for HPDIs.
This is the whole issue here. If I had a commercial version of the Yamaha I would not be having these fuel issues.
As for the original part of this thread, the poppet ( water control) valve, if I had been where this engine was originally purchased two years ago it would have been a warranty issue. That valve broke and stuck, and for some reason that part of the motor corroded away.
there is not one single new filter for this motor in this nation. Not one. None. Nada. Zipping on down to one of the many Yamaha dealers here and buying new filters just cause it feels good to change them, is not an option.
There is also no indication that there are any clogged filters. Bypassing the only one that I cannot clean made no difference. Removing another one entirely made no difference. Cleaning the other one made no difference.
I know you cant get parts locally, that's why I asked if you were waiting for them.. ordered from SIM... etc. I thought there was one filter you could not clean or change, but I guess you cleaned it. So where does this leave you as far as ideas? What changes after running WOT for 10 seconds that causes the RPM's to drop? Do you still feel garbage is still in the system somewhere and clogging fuel delivery. I guess that theory is out since you cleaned all the filters and they're as good as new. Auxilary tank made no change. Why does it take overnight until the motor will run WOT again if only for a few seconds? Does the motor being hot have anything to do with this. Is a piston starting to bind up in the powerhead? Coil failure causing a plug to drop spark. Vacuum leak..? Whats your plan?
Heck no, I haven't given up. I managed to find one of those all-metal oil cans to spray gasoline with, and a small bottle of propane as backup. As soon as the weather permits ( we have remnants of a TD going by) we will take the boat back out and try the old squirt-fuel-in-the-intake tests. We need calm water for that, as the cowling and intake cover will be off. We will decide which way to go next when we see if squirting fuel into an intake smooths out the motor. We need to be at the ragged point to do it, i.e. 3000 rpm. When I tried before, in the marina, we could not get up to anywhere near that speed.
Good to hear. If you have an IR temp gun, you might bring it along and test the cyl temps at the misfire point. One hot cyl might point you to a lean condition or a cool one might tell you spark has failed.
Be careful out there on the bracket with a can of gas in one hand and a propane tank in the other.
Good Luck 
