View Full Version : 350 tbi gm

05-25-2006, 06:39 AM
"I need help with the TBI unit. I have a 1994 indmar 350 GM and I am getting fluid in the vacuum line going to the MAP sensor. I was also told that the injectors were shot. My question is does anyone know the spec on the injectors, and is it possible to put a complete aftermarket TBI unit on. I was told that it would be a minimum of 350$ to rebuild the TBI and another 100$ for injectors. Summit sells a Holly unit for about the same price."

05-25-2006, 08:47 AM
"Your MAP sensor is on the side of the motor, below the throttle body, right? This is the reason they moved it in '95 (gravity causes fluid to collect in the hose). Make sure the hose to the MAP sensor has no leaks, get the liquid out of it and enjoy the boat. If you think you can move the MAP sensor and keep it in place effectively, you can do that. If it's sluggish now, that should clear up once the hose is dry but you may need to clear the code. If the sensor has anything in it, empty it and use a vacuum pump to make sure it's not leaking. If it is, you can replace it with the regular GM part.

Who told you that the injectors are shot? When it runs, do you see a continuous cone of gas going into the orifices? If not, spray the outside of the injectors with carb cleaner (nothing too harsh) and add a can of Sea Foam to the tank. If you do need to rebuild the throttle body (and I have never heard of anyone who did), shop around for the best price. Same for the injectors. I would stay with the Rochester parts."

05-25-2006, 09:38 AM
"I sent the injectors to a place called Marren Fuel injection to be cleaned because the spray pattern was very bad. They said that their was rust and it could not be cleaned and they could not get a part number off of it. So at the very least I would like new injectors and any information on the part # would be great. As for the TBI unit itself, the thinking for the rebuild is the fact that the vacuum line to the map sensor keeps filling with liquid. I have replaced this line in the past. The boat runs good when the line is clear but after less than a hour it fills again. So I will fix the location problem but I am concearned in the fact that it never did this before and why now is it. Also I would like to replace the MAP sensor itself, but I need help with the part number. I have a manual, but it is somewhat limited in part numbers.

Jim, thanks for the help."

05-25-2006, 10:03 AM
"Where are you located?

If you have a Mastercraft, you can go to or call one of their dealers and they can get the part numbers for you. You'll need to have the motor serial number to get accurate info. I'll look in my MC training notes for the reasons behind the hose filling. I haven't found it yet but I'm pretty sure it's in there."

05-25-2006, 10:10 AM
"I am in upstate NY, the closest dealer is 3 hours away in Lake George.

Does this mean you do not think a TBI rebuild is required?"

05-25-2006, 10:48 AM
"If there's a lot of rust, it may need looking into but I would probably do the injectors first. These are regular GM parts so if you want another opinion, ask a Chevy dealer how often they rebuild throttle bodies. I would imagine it's a rare thing for them to do. If I remember, the fuel pressure regulator has some effect on the MAP hose filling up with gas.

I would call the nearest dealer and get the part numbers. You could also call MC or Indmar technical to get the generic Rochester part numbers. Tell them that you don't have a dealer near you but you have a Chevy dealer near you.

In the future, spray some silicone over the motor, on the wires and on any exposed metal. This will minimize any corrosion unless you run on salt water."