1998 Mercury Promax 300 Fuel Delivery Issue?

[Dave Strong]

Thats the VST, fuel pump is in there at the ft of the unit.

Dave

[Basnova]

What does VST stand for, Vapor Separator Tank, or something along those lines? Anyone have experience testing or R&R'ing one of these?

[Dave Strong]

Not sure about 3.0L but 2.5 has a pressure port to check regulated press. If you take it apart you will need a new o-ring to seal the top, they enlarge when removed and will not fit.

Dave

[Basnova]

Yes, I see a Schrader valve on one of the ports, so it must be the same. When you say an o-ring, are you talking about a seal for the entire top of the tank, or do you mean where the schrader valve inserts on the top of the tank?

[Dave Strong]

Seal for the top of the VST. Sit down when you price it.

Dave

[Basnova]

Are you talking about this part number? GASKET (#98-8M6002520)

GASKET (#98-8M6002520)

GASKET (#98-8M6002520)

[Dave Strong]

Are you talking about this part number? GASKET (#98-8M6002520)

GASKET (#98-8M6002520)

GASKET (#98-8M6002520)

Sorry didn't see this till now, pn 809086.

Dave

[Basnova]

I finally got some time to eyeball the fuel lines, and can see there is new grey hose before and after the primer bulb. This must be what a shop installed when they replaced my bulb and some hose a few years ago.

The other day I spoke to the mechanic who rebuilt my lower end a couple of years ago. Like what you guys have already mentioned, he said there's a big problem with the new style fuel hose. When I told him I had some grey hose, he said that's the worst hose. He said he's been seeing two year old boats where their hoses are collapsing. He also said that even though I have fuel in my filter, it doesn't mean anything, and that that hose could indeed be my problem, and said that would be absolutely what he would look at first, just like you guys said.

There are some zip ties holding some hoses on, but where the grey hose connects, there some of these clamps pictured in the graphic below. Can someone please tell me how to remove this clamp? There appears to be a little tab that fits into a slot, and is bent down, in what appears to be a position so it can't slip back through the slot. Am I supposed to bend that little tab and somehow maneuver that tab back out of the slot? And, once I get it off, will I be able to put it back on, or should I use zip ties, or hose clamps, or...?

Also, if this ends up being my problem, or I want to test with a gas can and a different hose and bulb altogether, where do I get hose that doesn't have that inner wall like the new hose does?

[Dave Strong]

Those clamps are one use only and need the correct tool to install.

Dave

[Basnova]

How do you get them off, and what can I use in their place, if anything?

[Basnova]

And, can I use regular fuel line from an auto parts store, if I find a problem with that Grey line?

[Basnova]

OK, spent the time necessary to troubleshoot. First thing I did was have someone turn the key to the ON position to see if I even hear the fuel pump in the VST. Nothing, no sound at all. Next, I hooked a multi-meter to the positive and negative terminals of the VST pump. Good continuity. Switched multi-meter to 20v setting, and turned key. Saw 12.3 volts, but heard nothing. Obviously the pump is not working. Went onto Crowley Marine site, and it says fuel pump is Part# 809088T and it's $769! Is that for real? even worse, it's not longer available. Anyone have any thoughts for me now?

[Basnova]

Dave, thanks for pointing me to that o-ring seal number. I just ordered one, and also found a pump for the VST, which I just ordered. Now, all I need to do is find those clamps and the tool for it.

[JR IN JAX]

I replaced the one-time clamps with some Aviation spec-grade clamps from West Marine. They are not cheap but work well.

[Basnova]

OK, I'll check them out. I don't care how much they cost, as I only need a few. I wish I knew what sizes I need. I have two hoses with right angle bends coming from VST to brass housing with Schrader valve on it, which I assume or high pressure fuel hoses. They are stamped with 7.94mm. There is another hose of a similar size connected to a brass fitting at the back of the VST that has what looks like a special type of black zip tie. Then, underneath there is a tiny clear oil hose that also has that special zip tie, but it's tiny!