fuel pump pressure

[sailingwest]

Hi All, I have a 50hp 4 cyl 2 stroke mercury early 80s i am looking to fit an electronic fuel pump to this motor to assist built in pumps fitted to the existing carbs(2) can anyone tell me the operating pressure of these pumps at wot ? thanks for your help....Jim B

 

[Barnacle_Bill]

Re: fuel pump pressure

Pressure on those intregal carbs is only 2psi. I would highly recommend you rebuild the carbs and pumps.

 

[j_martin]

Re: fuel pump pressure

Keep it under 6 lbs, preferably around 4-5. Carter makes a couple of pumps that work great and aren't very expensive.

 

[Silvertip]

Re: fuel pump pressure

You are asking for real big trouble. Electric fuel pumps will continue to run even if an engine stalls or quits. In the event of a fuel leak, a stuck needle and seat in one or more carbs and you have an explosion possibility. There is also a timer/pressure switch that allows the pump to run momentarily to pressurize a fuel system. Without that function you could literally pumpy your engine full of fuel. It is against the law to fit non-marine fuel components on a boat. Electric pumps on I/O's (and your family car/truck) for example are wired through the oil pressure switch so if oil pressure is lost (engine dies) so does the pump. There is no such switch on a 2-stroke outboard and no convenient/inexpensive way to accomplish this function. Your engine was built with a vacuum/pressure fuel pump adequate for the job. As was suggested, rebuild the pump if needed.

 

[Scaaty]

Re: fuel pump pressure

You are asking for real big trouble. Electric fuel pumps will continue to run even if an engine stalls or quits. In the event of a fuel leak, a stuck needle and seat in one or more carbs and you have an explosion possibility. There is also a timer/pressure switch that allows the pump to run momentarily to pressurize a fuel system. Without that function you could literally pumpy your engine full of fuel. It is against the law to fit non-marine fuel components on a boat. Electric pumps on I/O's (and your family car/truck) for example are wired through the oil pressure switch so if oil pressure is lost (engine dies) so does the pump. There is no such switch on a 2-stroke outboard and no convenient/inexpensive way to accomplish this function. Your engine was built with a vacuum/pressure fuel pump adequate for the job. As was suggested, rebuild the pump if needed.

Yep, just probably need new diaphragms on the pump/s...don't re-invent the wheel here

 

[sailingwest]

Re: fuel pump pressure

thanks all for advise,with regard no easy way to fit pump kill switch i was going to use the plug on cyl head where the water pressure switch would go if fitted ,i have already set up a relay to switch on pump @2500 rpm and the pump i was looking to use runs at 2psi with built in pressure relief ,i feel that i have a safe system do you think i should abandon this modification i really dont rate diaphram pumps .....Jim B

 

[sailingwest]

Re: fuel pump pressure

ps ,the pump is a marine rated pump

 

[j442w30]

Re: fuel pump pressure

Why do you think that you need to add an electric fuel pump to this engine? If the pump that is on there now is not working why not just rebuild it? Rebuild kits for fuel pumps are about $10 max. I rebuilt the fuel pump for my 40 horse Mercury (4 cylinder) and it only took about 15 minutes, way easier than the carbs. Instead of spending a lot of time and money on an electric pump and the necessary plumbing and wiring, just fix the part thats not currently working. Sorry if I come off a bit harsh but I do not understand why you would want to attempt something like this.

 

[sailingwest]

Re: fuel pump pressure

Why do you think that you need to add an electric fuel pump to this engine? If the pump that is on there now is not working why not just rebuild it? Rebuild kits for fuel pumps are about $10 max. I rebuilt the fuel pump for my 40 horse Mercury (4 cylinder) and it only took about 15 minutes, way easier than the carbs. Instead of spending a lot of time and money on an electric pump and the necessary plumbing and wiring, just fix the part thats not currently working. Sorry if I come off a bit harsh but I do not understand why you would want to attempt something like this.

in the good old US of A re build kits are cheap however in europe they come in at about ?25 or $50 US dollars per kit dont know why Mercury feel the need to rip us off but there you are....Jim B

 

[Scaaty]

Re: fuel pump pressure

Its just a rubber daiphram..probably a few bucks. ..make sure you have the CORRECT part number, and when you get it COMPARE so its the same as the old...I've had some right number, wrong rubber more than once..its just the way things are nowadays

 

[j442w30]

Re: fuel pump pressure

Sorry Jim I did not understand your situation. I have seen on other threads that prices for Mercury parts are incredibly expensive in your part of the world. Did you take your fuel pump apart? Is one of the diaphrams torn or is it something else? I would think you could order a kit off the internet and have it shipped to you, might as well order 2 just in case. Good luck with the repair.

 

[sailingwest]

Re: fuel pump pressure

ok folks ,it would seem that i should abandon my plans ,thanks for your advice new rubber it is.thanks again ...Jim B

 

[sailingwest]

Re: fuel pump pressure

Sorry Jim I did not understand your situation. I have seen on other threads that prices for Mercury parts are incredibly expensive in your part of the world. Did you take your fuel pump apart? Is one of the diaphrams torn or is it something else? I would think you could order a kit off the internet and have it shipped to you, might as well order 2 just in case. Good luck with the repair.

hi, the rubber is not split but in is badly stretched ,the engine runs for a couple of minutes at wot then bogs down to about 2k rpm if i pump the ball it will pick up ,i have cleaned and set up carbs checked spark across range and all is good....Jim B

 

[sailingwest]

Re: fuel pump pressure

well i went ahead with fitting electronic pump and it runs like a dream ,thanks to all Jim B