VST diaphram...I think...
 

I have a 1997 Baja 252 with a 502 mag. I was out at the lake this past weekend, and after funning it hard for about 10 minutes or so, i came off plane, and it began sputtering and then died. It wouldn't fire off unless I held the throttle wide open, then it would start, but run super rich, so much that my boat transom and swim platform turned black. I was running with my brother and cousin, who are both a lot more engine savvy than I am, and they narrowed it down to the VST. We took a zip tie and restricted the clear intake hose from the water pump, and this got me through the weekend with no more problems. They said that it was probably the daphram in the VST, so I'm going to start there. My question is, does Merc still make a rebuild kit for the VST? I can't seem to find one online. Either that, or my google-fu is off today. Also, does it sound like I'm on the right track? Any help would be appreciated. How difficult is it to rebuild the VST, I'm retty decent with a wrench, so I don't mind giving it a shot. Also, I'm going to change the oil just in case some gas leaked past the cylinders, is there anything else I need to do once it's fixed?

The VST is like a carb float bowl. You may have some crap in the needle and seat which is causing it to overflow into the clear hose.

All the parts are here:

http://www.mercruiserparts.com/Show_...SEPARATOR+TANK

Thanks for the reply, first of all, but my mechanics in the family think it's the diaphram, so I ordered one from Merc, and we'll see what happens. I'll clean everything when I pull it all apart.

You have a mechanical pump that feeds fuel to the high pressure efi pump in thr VST. If you have fuel in the clear line from the mechanical pump, it's the diaphram in the mechanical pump, not the vst. Also, if your mechanical pump is driven off the water pump, that lube reservoir will be contaminated with gas, drain and refil.

My mechanical fuel pump diapham went bad and did the exact same thing. I replaced my mechanical fuel pump and changed the sea pump gear lube. Problem solved.

Check my posts on page 5 of the wasn't the fuel pump thread if you need all the vst part numbers and some good info. If you have fuel in the clear tube though it probably isn't the vst. Might be a good idea to change that diaphragm though if it hasn't been done. Apparently ethanol eats away at it