Mercruiser Fuel Pump

[frostywalrus81]

Ok I have read and read and read different things online about this. I have a 1971 165hp Mercruiser. My fuel pump only has 2 ports, 1 being a Fuel inlet and 1 being a Fuel outlet. I don't have the port that goes to the carb if the diaphram busts. I am wondering if I can change it out with an auto fuel pump since it doesn't have that extra port. The fuel pump on it right now is a Marine fuel pump so I am not sure what the difference between the 2 pumps are. Thanks

 

[Bt Doctur]

Re: Mercruiser Fuel Pump

you do have that port (threaded on the bottom or side)
it`s there and someone plugged it off(diaphram wont pump fuel)
or someone already replaced it with a auto pump.
The diaphram must be vented to allow it to go up and down,this moves the fuel thru the valves in the pump body.The vent line is there to tell you the diaphram has ruptured and instead of leaking into the bilge it goes up to the carb.

 

[frostywalrus81]

Re: Mercruiser Fuel Pump

does anyone have a picture of how this fuel pump is supposed to look. thanks

 

[HT32BSX115]

Re: Mercruiser Fuel Pump

I had a 66 boat with a Mercruiser 150 (230 cu-in 6)

I don't remember a clear line up to the carb either. It may not have been required back in those days. (it didn't have an anti-syphon valve either and the tank was much higher than the engine and fuel lines)

It would be a good idea though to get a pump with the connection though. It's a LOT safer!

 

[HT32BSX115]

Re: Mercruiser Fuel Pump

The following is from Doug russell. It's a terrible picture

http://www.dougrussell.com/partscat...BlockNumberList=10,6,9,11,3,7,13,8,4,12,2,5,1

 

[ziggy]

Re: Mercruiser Fuel Pump

I had a 66 boat with a Mercruiser 150 (230 cu-in 6)

I don't remember a clear line up to the carb either. It may not have been required back in those days.

this is what i was trying to say in the other thread. http://forums.iboats.com/showthread.php?t=312278
it's the crux of the matter. like i said in that thread. i don't believe that the extra fuel dump to the carb showed up untill 78. (when service manual #3 came out)(i've had 2 L6's, one a 72, one a 75, neither have had the clear fuel line to the carb, both had what appeared to be auto fuel pumps)(both service manual #1 and #2 do not refer to anything other than what i think is an auto fuel pump, no mention of any clear line up to the carb) me personally. if i was gonna replace my existing fuel pump. i'd get the new version and plumb in the clear line up to the carb. i think fishermark did it and it looked real good and also looked like it'd meet todays standards. which would be much safer than the way it came from the oem in the years in question.... if your needing to replace it, use a new style fuel pump imho...

 

[windsors03cobra]

Re: Mercruiser Fuel Pump

Here is what the fuel pump on my 78 156/250 looks like, carter style with the filter on top. I believe mine is original and I was thinking of replacing it after 30 fricken years but $100 for marine type. I was thinking of going $25 auto style.
I kid, I kid.

The vent line to carb on mine has 30 years of patina, what is it green there looks like Prestone. :redface:

 

[frostywalrus81]

Re: Mercruiser Fuel Pump

ok every time I see a picture of the fuel pump for my boat it is shown like this.

Now on my motor it is mounted w/ the filter on the top.

Is this correct or was the last owner an idiot.

Thanks

 

[windsors03cobra]

Re: Mercruiser Fuel Pump

Pretty sure it goes a little something like this.
Filter on top=old style Carter, filter on bottom=new style Carter. Both are available for about $100.
http://www.amarket.com/fuepinli.htm

 

[frostywalrus81]

Re: Mercruiser Fuel Pump

ok so I have bee talking to a lot of people and have gotten a good idea from one of them and I wanted to run it by you guys first. I have the fuel pump without the return line. Someone told me that when the diaphragm bursts the pump will lose it's pressure causing the motor to die thus fuel would not leak into the hull. Let me know your opinion. Thanks guys

 

[JustJason]

Re: Mercruiser Fuel Pump

Someone told me that when the diaphragm bursts the pump will lose it's pressure causing the motor to die thus fuel would not leak into the hull. Let me know your opinion. Thanks guys

Stop listening to that person. Diaphragms's dont burst, they tear. And they will usually start with a slow tear that gets bigger and bigger with time. A pump with a very small tear may still not have a problems maintianing fuel pressure for WOT, it's only a couple of psi. So I don't buy the motor dieing.
A classic symptom of a failing fuel pump is an engine that won't maintain WOT, and it gradually gets worse.

 

[mkast]

Re: Mercruiser Fuel Pump

You see that yellowish looking bowl under the pump?
That is what was used before the clear hose to the carb.
You have the marine application pump.

 

[frostywalrus81]

Re: Mercruiser Fuel Pump

You see that yellowish looking bowl under the pump?
That is what was used before the clear hose to the carb.
You have the marine application pump.

What do you mean that is what was used before. That is the fuel pump filter housing. I doesn't have anything to do with what the clear hose does on newer pumps. Besides My fuel pump filter housing on mine is on the top of the fuel pump not the bottom, so there for it wouldn't protection fuel from leaking out it would merely gravity feed the fuel down into the pump.

 

[ziggy]

Re: Mercruiser Fuel Pump

I have the fuel pump without the return line. Someone told me that when the diaphragm bursts the pump will lose it's pressure causing the motor to die thus fuel would not leak into the hull. Let me know your opinion

the short of it is. if your gonna replace it. replace it with a new style marine fuel pump. similar to this... http://www.ebasicpower.com/pc/MAL9-35419/ALL4C/Fuel+Pump,+Inline+4,+6,+Mercruiser+3.7L,+60032

if the diaphram ruptures on your present set up. it will leak into the boat. one way or the other. fuel fumes... kaboom if it finds a spark.

if your absolutly set on going with what you have, ya might check out the mercruiser dealer and see if the diaphram is still available. it looks like it might be, item #3... http://www.mercruiserparts.com/Show...br=983&bnbr=30&bdesc=FUEL+PUMP+AND+CARBURETOR


just keep in mind. if you don't go with the new style marine fuel pump. by todays standards, your taking your life, your familys life, and any one in close proximity to you life in your hands. if you blow, if you live, you'll probably be sued till you've got nothing left. your insurance company probably won't pay either since they'll probably come find this thread and find out you knew the difference from a auto vs marine fuel pump. you've been educated now, so if you decide to replace it. make the right decision and replace it with the newer style marine fuel pump and be upgraded and much safer.. windsors set up looks good to me......

 

[frostywalrus81]

Re: Mercruiser Fuel Pump

Oh I already planned on going with the Newer style pump anyway. I just wanted to know the difference between the two so that I know what to tell people I know that it's not a good idea to use an auto pump so they don't blow themselves up. Thanks for all of the input guys.

 

[mkast]

Re: Mercruiser Fuel Pump

I doesn't have anything to do with what the clear hose does on newer pumps.

Prior to the hose application, fuel pumps used the bowl.
When you see any fuel in the bowl, replace the pump.
Look at #5.
It's a fuel pump sight glass.
That's what's under your pump.

 

[Fishermark]

Re: Mercruiser Fuel Pump

Here's the pump I used:

Here is where I routed the clear tube: