i just purched a 1994 baja 272 with a 502 mag efi. the mechanical fuel pump was leaking so i had a new one put on and new seals and bearings put on the sea pump.
i took the boat out and noticed a smell of gas. so checking around for leaks found out it was coming out the exhaust on the starboard side. the boat runs good doesnt miss or anything just alot of gas on the water..could it be an injector stuck? any help would be great..thanks

It could be a stuck injector, but could also be cause by a couple of other things. Bad fuel pressure regulator, which should be on the front of the injector rail. Not sure what years they had the VST tank with the high pressure pump on it, but it has a float w/neddle and seat that could be stuck or dirty. It would be located on the back side of the plenum on the port side. Any extra fuel there would dump right into the intake causing a very rich condition. Either way you need to find the problem ASAP because it will wash down the cylinders, get in the oil and you will be rebuilding the motor soon.

It may be the diaphragm in the Vapor Separator Tank (VST). The diaphragm develops a very small hole that allows fuel to leak through the vent line into the intake manifold. This fuel leak allows raw fuel into one or two cylinders on one bank of the engine and the raw fuel shows up in the exhaust. You will need to remove the top of the VST, be careful not to strip the screw heads they are usually difficult to remove, and replace the diaphragm. You will need a new o-ring to seal the VST; I believe the part number is 25-803831, and a diaphragm kit. Make sure you install the diaphragm kit correctly; there are two different positions for the spring.

Thanks for the replies. It seems like its pointing to the vst. I have been online and trying to find out more about it. It did have a little bit of blue smoke coming out the starboard side also.
im going to have a friend put a merc scan tool on it. Will that tell us if it is the vst or an injector?

I think the only thing a scan tool might help with, is to shut off the individual injectors so you can check for a drop in RPM, but it won't tell you anything about the VST tank.

28 eliminator, thanks for the reply, i think i take the vst tank if and start with looking at the needle and seat and diaphram. I just checked the oil and it smells like gas and is a touch over the full mark.

It sounds like your oil is contaminated and i would change it right away. Pull the vacuum lines off the VST and see if either has gas in them. On top of the housing is a plug that you could pull off and see if fuel starts over flowing out of the top when the motor is running. If it does, then you know the neddle and seat are not working and probably just need cleaned. As GMC271 stated it could be that diaphram. I would probably buy a new diaphram seal kit and maybe screen for the fuel pump. It is almost impossible to reuse the stupid o-ring seal for the top cover, and you don't want to have to take it back apart.

Its your diaphram in the VST. I had the same problem last spring this spring. Last year before I bought my boat the shop replaced the #8 injector "thinking it was the problem". Nope wasn't a "stuck open injector". Rather the $85 diaphram in the vst.

Then I had the same thing AGAIN this spring on start up. So I said f*** it and fixed the problem for good. No more venting to #8 cyl. Rather it now goes back to the tank It can fail all it wants now. Total cost was less then $20 for some fuel line and fittings. Took about 30 mins or less to install. The return line fallows the fuel line form the mechanical pump to the vst

One nice thing was that my Baja was already plummed for twins from the factory. So I already had a extra fuel line running from my tank.





Inside the VST





This is the diaphram that has failed. Merc is Very proud of them at $85+

28 eliminator,
thanks again for the reply, is it safe to run to check the vst pump, with fuel in the oil? also i am concered about the time i did run it to get back to the dock. upwards of 1-2 hours. with the fuel dumping into the cylinders? concered about the wash out on a cylinder?
i will be checking it this evening.

92nsx,
that is the exact same vst as mine. and the pics you posted are GREAT.. i was just looking for pics or videos on whats inside of the vst. know i have a good idea thanks to your pics.
thats a great idea to run it back to the tank......

Now that you know about where the problem is at, I would go ahead and change the oil before starting it again. It won't take long to find the problem and fix it. I am not too concered about the 1-2 hours as long as it's running ok now, but don't take any chances with the oil in there right now. Even if you put cheap oil in it to begin with, at least it is pure oil and not gas/oil. Your bearings and cylinders will like you for it.
92nsx, Great pictures also and I like the easy fix idea of running it back to the tank. My guess is that the ethanol in todays gas is killing that diaphram.