VST Filter Change - The Hull Truth

John_Madison CT · 10-29-2004, 01:11 PM

SIM: I too have a momentary RPM drop on my Yamaha 250hp OX66 ('98). As far as I know, the filter was NEVER changed with probably 5-700 hours on the engine.

Tell me, is this something I can tackle myself? I have the Yamaha manual too. It appears as though I can just remove the 3 bolts holding the VST to the block, then unscrew all those small phillips screws, which would drop the VST Bowl. Is that correct?

Otherwise, can I please get a quote on a new VST filter for this year engine? My email is: jmetaxas@aol.com

Thank you,

John

SIM · 10-29-2004, 01:37 PM

John,

I actually am in the process of installing a new powerhead on a F225. Not your exact engine but*I have the VST tank off of*it and will post some inside pics shortly.

Andy

John_Madison CT · 10-29-2004, 02:10 PM

SIM: Wow, that would be great. I'd love to see it.

John

GWcpa · 11-02-2004, 01:06 PM

Andy,

Ever get those pics? I need to do this to mine as well. Is it pretty straight forward to do? Any problems getting the air out of the VST afterwards, or does it prime easily?

I should get other parts from you tomorrow, so I will probably do the filter cleaning at the same time.

Thanks,
Ian

SIM · 11-02-2004, 07:19 PM

Finally getting around to this....sorry it took so long.

This is a VST (Vapor Separator Tank) off a F225 2003 Yamaha. All 4 and 2 stroke Yamaha EFI, HPDI and 4-Stroke EFI are going to have some version of this type of tank. They all are very similar in how they*function. Some maybe be easier to remove from the engine and some are a little more involved. Either way I find it easier to remove the tanks right from the engine and clean it*them on a bench. It also helps to have a Yamaha service manual handy so you kind of know what you are getting into before you start. Might not be a project for everyone. I would say its a little more difficult then changing a water pump impeller.....but like that*type of*service....*once you do it..... it wasn't that hard.....or was it?

I start by bleeding off the fuel pressure. On or around most VST tanks there is a valve that looks similar to a tire valve on an automobile tire. Put a rag over it and press the valve in to relieve the fuel pressure. Fuel will come out so make the necessary precautions to catch it*and make sure it does not blast you in the face. Remove the VST tank from the engine. You will have to disconnect a few fuel lines so have a small pliers and needle nose handy to squeeze the clamps for sliding back. Label the hoses if you are not sure what goes were. Better have a 10mm socket handy too.

Here is what it looks like when it's off:

The cylinder shaped piece to the left is the fuel pickup pump. Its electric on the F225 and F200. HPDI, EFI and other four strokes this will not be there. You all have manual fuel pumps.

Now remove the 6 or so screws that hold the cover in place. Even though it’s a combo Phillips and flat head fastener head type,*I use a flat head and make sure it’s the right size. These screws are small and tend to be tight. So tight I usually try tightening them first (you will hear a small crack) and then loosen them. Don't strip the head because it’s obviously a pain to deal with that. After the screws are off, go ahead and lift the lid....this is what you get:

The filter is at the base of that electric fuel pump. Its*the black*rubber piece with the screen built in. On a F225 its just pressed on with no mechanical type fastener. Be careful on the re-install. The fuel enters from the left side opening.

On this one you can see there is some crud in the screen that is blocking 40-50% of the area. I use carb cleaner and blast it out. Then go ahead and look in the tank for crud at the bottom and clean that as well.

Now assemble it in reverse order and inspect the o-ring on the tank cover and replace if needed. Once its back together go ahead and re-prime the fuel system. Pump the bulb till firm then cycle the key switch several times. Once*hooked*up to water or the boat is launched*go ahead and start. It may run crappy for a short bit but will settle down in no time.*

*FYI...... on this particular engine the customer*has installed*in the fuel line*a Yamaha water separator (Racor style)*and the fuel filter that’s on the engine. Also has religiously ran Yamaha Ring Free. 1650 hours of running time and that’s the first time the tank was removed. I would recommend all owners not waiting this long before checking. I don’t think its something that needs to be serviced every 100 hours but at*the first 100*hours*I would suggest checking it. There are lots of horror stories out there with brand new engine's and this filter being clogged. Who knows how it happens.*

After the initial check I would do it every 250-300 hours thereafter. More often if the only fuel filter is the engine mounted one.

Hope this helps,

Andy

MDT · 11-02-2004, 08:21 PM

Andy,
Here is a tip for getting out those small screws. Try a hand-held impact wrench. The kind you tap with a hammer. Mine has a 3/8" socket drive and I have purchased several sizes of straight and Philips head bits. Back when I ran motorcycles (1970's Hondas), they were all assembled with aluminum screws. This tool was a must. When I graduated to boats, I carried it over and I carry it on the boat with me. Last Saturday, my neighbor was winterizing his outdrive. He could not remove the lower unit lube screws. He had the slots pretty much screwed up. I hit each with the impact wrench and the correct size bit and they popped right out.

Also, for my F115's, I see in the shop manual the filter you speak of. Will place this on my spring maintenance list. Thanks for the tip.
MDT

SIM · 11-03-2004, 11:15 AM

Thanks for the pointer MDT. I have one of those tools*but on these tanks the availalbe room along the cover is not much. The impact tools tend to be a little bulky.*

Thanks,

Andy

GWcpa · 11-03-2004, 12:12 PM

Thanks SIM. Great write up. Got my parts from you today, so I'll get working on it this afternoon, I hope.

John_Madison CT · 11-04-2004, 07:19 AM

I'm going to do my filter this Friday. I believe that mine has never been changed after 600-700 hours of use too.

Gonna be interesting just how clogged it is.

John

pthein · 11-12-2004, 05:22 PM

Did you get those filters changed? Wondered how dirty they were etc?

John_Madison CT · 11-13-2004, 09:10 AM

Pthein:

No, not yet. Too darn cold here lately to deal with tiny screws. I did clean the O2 sensor and it was remarkably clean after all the hours I put on this engine.

John

pthein · 11-13-2004, 11:25 AM

Thanks for the update. I am curious to learn what you find when you finally get to that VST.

Any chance you have some pictures you can post of what your O2 sensor looked like when you got it apart?

Phil

John_Madison CT · 11-13-2004, 05:02 PM

Phil: I didn't take pics of the 02 sensor, but really should have. It didn't have any clumps of carbon on any of the small opennings on the bottom tube of the sensor. Regardless, I soaked it in both Yamaha Combustion Cleaning and also Carb and Choke cleaner for 2 full days.

The transfer tube had some carbon on the outside of the cylinder, but nothing on the inside orafice.

The O2 sensor holder had some carbon on the internal walls, but nothing that would have affected performance.

All in all, it appears that Ring Free and a properly adjusted Oil pump should lead to a clean sensor.

John

pthein · 12-05-2004, 02:09 PM

Did you ever get a chance to clean that VST tank? Was wondering what you found. I am getting ready to clean mine at the end of the month and was curious...

Thanks

John_Madison CT · 12-06-2004, 02:05 PM

pthein: No, not yet. Boat is in my yard and pulled for the season. I gotta find a warm day and I will attack that filter.

John

JoeBagadonuts · 12-06-2004, 11:18 PM

I just did the VST on one of my 2001 150 HPDIs (650 hours total time). I don't want to say I was disappointed, but there wasn't a whole lot in there. Kind of a PITA to take apart and put back together, too (the O-ring for the top of the VST is an adventure to get back on). But then I did it without removing the VST from the engine, since I didn't have the part that must be replaced if you remove the tank (fuel line clamp).

SIM · 12-07-2004, 10:33 AM

Joe,

At least you now know its clean......

Andy

gman25 · 12-07-2004, 12:28 PM

Joe,I thought the same thing the first time I cleaned my VST filters on my 2002 200 HPDI. You wont really find glops of stuff in the filter from what I have seen or heard, but you will notice how dirty it is if you hold it up to light. If you have a clean one and compare it to the dirty one holding them both up to light,you will see what I am talking about. The nice thing about that filter is that you can clean it with soap and water.

JoeBagadonuts · 12-07-2004, 09:09 PM

gman,

Good idea about holding the filter up to the light. Wish I had thought of it. As it was, I didn't put a lot of effort into cleaning the filter since it didn't look like it needed it. As for cleaning, I would think hose it down with carb cleaner and compressed air...? Not sure about soap & water. For sure I would not want to get my hands on the filter mesh, it's so incredibly fine there's no way it could hold up to much of a "scrubbing."

Also agree with SIM...glad not to find a bunch of cr@p in there!

gman25 · 12-08-2004, 02:41 PM

Joe, I couldnt get my one engine above 2800 rpm's before I took my VST tank apart. I asked my dealer and he recommended the soap and water idea. As you can see, its a very fine filter and I would be very careful about spraying air or anything else into it with the possibility of blowing a hole in it. To buy a new one is a little on the pricey side(about $60). I was also "upset" when I didnt see any obvious obstruction in the filter. When I asked the dealer his opinion,thats when he told me about holding it up to the light. Comparing the two was like nite and day. I cleaned it in the sink, put it back together and it ran like new. I also cant say enough about the anti-enzyme additive I have been adding to the fuel. I dont know what state you live in,but NYS is adding ethanol to the fuel and it has been causing alot of problems with the outboards,especially the yamahas.The additive I have been using is called soltron(solpower.com) and the engines have been running better then new.