mercruiser sucks

"That guy should be fired"

(in my best Beavis & Butthead laugh) ha, ha, fired, cool, ha, ha.

I have a marine starter and alternator thank you. And the carb and intake are marine, from a merc even. All i will do is disconnect fuel electric parts and hook gas line to the carb. The fuel pump in question said on the package "auto or marine applications" I think we are over thinking the situation. and yes tomorrow i will try to clean the injectors before i try the carb swap. I didnt know that fuel pumps were made to shower sparks everywhere i wonder how cars drive around without blowing up.

Because vehicles have a constant mass airflow whereas your marine motor is sitting in a box with poor airflow and fumes can build up. So your solution still doesn't cover the vent overflow which a carb has and fuel injection doesn't which was the whole purpose, not due to any "showering sparks" as you say. I think we're all here just trying to help but if you're good with it put it on.

are you talking about the return line back to the fuel water filter?

(Message edited by dh03r6 on March 04, 2008)

Not sure on a fuel pump, but in some auto applications (carb) the overflow is set up to dump out under the car onto the road. That would be the prblem of using these parts in a boat (closed enviroment) that are designed for a car (open enviroment).

My personal experience with trying to save money and use auto parts on my boat was dismal. There were a few item that worked fine (fuel lines being one), but most of the main components just had too many issues.

good luck. I went through a very similar experience with my first boat, got it at a bargain since it had sat for years. The previous owner had even put a new motor in. I had it checked by a mechanic, water tested ,everything. I owned the boat two years and ended up replacing the motot (the previous owner did not do it right and the motor dropped a valve) replacing the carb (the owner put a 750 instead of a 650 on there) and fixing the floor.

Donald, In a marine carb application the carb vapor/fuel overflow tube which exits the right side or rear runs from the carb to the fuel pump. Typically on the fuel pump you'll have a fuel inlet and outlet facing forward and a nipple at the top of the pump where the carb overflow attaches. This prevents the fuel from dumping into the bilge. Here's a pic of a typical Mercruiser fuel pump. The pump on my '95 looks similar to this as have others i've seen up to '99, not sure after that.

My 2001 EFI merc had the vapor lock problem only in the winter months (still in florida though). There were no problems with the motor or any other part. It must be a design problem that the engineers deemed an additional, in-line, fuel pump was the corrective action. After the install I have had no other ocurrences of the problem. It would occur after running for a while then sitting with the engine box closed for a certain amount of time and it would take some time and cranking to get it to fire off.
Oh I havent heard anyone mention the advatages of EFI over carb as far as fuel efficientcy goes. EFI is head and shoulders above the carb and with the fuel prices having no cap in sight why would you opt for the "long term" more expensive way out? Getting just .5 gal/hr less would cost about $400 running approx 200 hrs/yr multiply that by say 3 years, not taking into account any further increase in fuel, and your looking at $1200

The reason i went carb is because the boat also has electrical issues and i didnt even know if the engine would run. so in theory 700 for new injecters 1300 for an ecu then what if something was wrong with the engine or tranny. this way carb for 300 get it running, time it, see if it floats, see if the tranny works. work on the efi during the winter then sell the carb......... update it runs now but not very well still working out fuel issues i think 750 is to big and i need to time it.

"update it runs now but not very "

I also believe a 750cfm is too much for a stock 5.7. Jet it down and it should work ok. I think you may find the most problem with the fact that you removed the F/I. With out throttle input from the TPS to the ECM, the timing may not be advancing.

I'm pretty sure that overflow vent on the marine mechanical fuel pump is to actually allow fuel to spill out in the case of fuel pump diaphragm failure. It should go the the flame arrestor or to the airhorn, similar to the PCV venting. You can use a regular fuel pump, you just will have fuel spill into the bilge if the pump diaphragm fails. Sometimes it is called a "sight tube" because the tubing will be clear and allow you to see the pump is going bad. All carb overflow is taken care of by "J-tubes".

TM...jetting it down will likely not fix the problem. You are right it is too much for a 5.7 stock. If he were to go down in jetting, he would have to adjust the high rpm mix on the carb, and I doubt he is going to get enough adjustment to have it run right when the butterflies are full open pumping down the throat. It will be leaned all to hell and he will start turning ceramic spark plugs into ash.

(Message edited by olSkoolTige on March 12, 2008)