Fuel pump and carb questions

[Fishermark]

Engine serial number: 2917271
Mercruiser 165

I installed a new fuel pump and had the carb professionally rebuilt. I have a few questions as to what goes where?.

I know the lower barb fitting on the fuel pump takes a clear hose that runs to the carb, but here are my questions:

1. Regarding the clear line - is the clear hose you can buy at your typical Home Depot good for that use? (In the plumbing section)

2. My carb only has one obvious place for the hose to go - the problem is I have two hoses that need to connect to the carb. One from the valve cover and one from the fuel pump overflow. (At least I know where the main fuel line goes in and can eliminate that as a possibility. ) Do I simply put a tee in the line? Or?.

3. From the picture of my carb below, there is another fitting / plug below the barb fitting. I assume that is a vacuum port - should I remove that plug and replace it with a barb fitting? If so, which line goes where? Clear line from fuel pump to lower fitting, and valve cover line to the upper fitting? or visa versa.

Thanks in advance!

 

[ziggy]

Re: Fuel pump and carb questions

ya know i ain't the pro, but i'd say the valve cover goes to the fa. the overflow goes to the top of the carb......i have a 72 and a 75 L6. the 72 had no provisions for blowby from the valve cover to the carb. it had a filter type oil fill cap and that was it. the 75 has the valve cover blowby hole in the middle of the valve cover, not comeing out the side like yers is.... the fa on the 75 has a fitting on it. just screwed to it as a fitting for coming from the valve cover. gonna see if i have some pics.

nice lookin fuel pump, what's ya got there? is that oem or serria or glm or? i need one.......

as for the clear hose. i'm researching it too. there seem to be a couple of different clear hoses from merc. one is nla, the other is available. mighty pricey too. from memory, 45-90 dollars depending on which one. must be something special about them. other than it's from merc.....

is that a mercarb? it don't look quite like my 2gc......

from my 72 L6... vent from fuel pump fitting. as ya can see from the pic below, i aint hip. i have an auto fuel pump and a plug in the carb on the 75....that'll change....

from my 75 L6.... the 72 fa don't have the fitting...

 

[tommays]

Re: Fuel pump and carb questions

If you go to GOOD lawnmower shop they have the clear/yellow line in many sizes that is fuel proof

The E10 and time has made me visit there collection many times in 2007 for my gas powered tools



Tommays

 

[MikDee]

Re: Fuel pump and carb questions

That lower fitting looks like a vacuum port for a power brake booster on a car? Is this a marine carb, or an automotive carb? Without physically looking at the carb, or it's inside passages, It's hard to tell but I'd say just get a brass plug the with right threads, to block off the lower port. I would also guess the fuel pump vapor "safety" line would go into the upper airhorn somewhere of the carb, (I'd use the Home depot clear hose because it really is an unused redundant line) and the line off the valve cover should go into the flame arrestor somewhere. This is not gospel, but the way it appears to me. Wait, if there's no other barbed fitting on the carb for the fuel pump vapor line, then it must be an automotive carb.

 

[starsnstripers]

Re: Fuel pump and carb questions

Use auto parts gas line, petrolium resistance! Not home depot plastic that will disintegrate just from the fumes. And i'd venture to guess it's an auto carb which shouldn't be used on a boat because auto or marine,one has a "J" bowl and one doesn't for waves and water swish swashing. Does your fuel line into the bowl enter at the top of the bowl or the bottom? I believe if it enters at the bottom it's an auto. It's something to look into before you use it i'm sure more qualified answers are on the way hang in there. Just my opinion on the subject from what i've heard here on iboats.

 

[starsnstripers]

Re: Fuel pump and carb questions

And do you have a pic of the main fuel inlet to carb? I agree w/mikdee brake booster vacume port at the base.

 

[Fishermark]

Re: Fuel pump and carb questions

I appreciate the concern about using an automotive carb versus a marine carb. This carb was on the boat when we bought it, (I know that doesn't mean it is necessarily marine of course), and the carb shop was informed it was off of a boat. So I believe it is marine.

It also looks like the carb described in the manual - even with the big plug below where a brake booster from a car would be plugged into. Here's the manual:

Here's another shot of the carb:

The only reason I asked about using the clear nylon tubing (or whatever it is made of) from Home Depot is I seem to remember DonS as saying it works just fine.

Ziggy... Regarding the fuel pump. I ordered it from Aftermarket Marine, and on the box in has the following:
AM 1399-01815
Replaces MC 86234A 4

 

[Fishermark]

Re: Fuel pump and carb questions

By the way, starsnstripers, sounds like we are working on similiar boats. Be sure to check out my ongoing battle with the trim system - similiar to yours!

Trim post

 

[starsnstripers]

Re: Fuel pump and carb questions

Yes Mark we are, mine is in the 69-70 era.There's a few of us L6 people on here thank god. They have been very helpful to me. My trim problem is solved just missing a very important part is all. "trim sender/actuater" I got my boat in parts/pieces with the weathered rebuilt 250cid laying in the engine compartment sideways with loose plugs to the weather. A basket case for sure, but i like a challenge. I got Iboats LOL and guys like Don, Achris, Ziggy, Bondo,Ron7000, Lakester,etc. we're in good hands. I remember Don saying that in a thread about the clear line too. That fuel pump is just like mine marine with the safety dump that goes up to that upper barbed fitting.

 

[starsnstripers]

Re: Fuel pump and carb questions

Maybe thats an older one brl from a 160? I think i have one of those in my basket case of parts i'll look at it.

 

[ziggy]

Re: Fuel pump and carb questions

i think it's a 2gc. mine is the one that looks odd. i agree with fishermark. that big plug in the thottle body assy. shows up in the service manual. if ya look at my pic. i don't have that plug. why i don't know. that carbs off my 72. ain't looked at the 75, it's out in the cold under cover....

 

[Bt Doctur]

Re: Fuel pump and carb questions

To help clear up the misconception
the vent port must be kept open or the diaphram will not function properly.
the clear hose from this fitting must go to the carb /carb body/flame arrestor .
The vent allows the diaphram to move the fuel. plug it and the diaphram wont work.
If/when you do see fluid in the hose ,it means the diaphram has ruptured and you dumping fuel into the engine oil also.Thats why you need a "marine pump", a car pump will dump this fuel in the bilge and your a candidate for the "Darwin Award"

 

[starsnstripers]

Re: Fuel pump and carb questions

Oh and i forgot Doc in my list of helpful peeps, MY Bad! SRY DOC. Going to look at my carbs BRB

 

[starsnstripers]

Re: Fuel pump and carb questions

Here's the one on my 165 it's like ziggys and i have the same fuel pump as you "marine" I'll check the other cab i have

 

[Fishermark]

Re: Fuel pump and carb questions

This is a great discussion and raises more questions than answers however.

Does someone know for sure where the two hoses/lines are supposed to go?

 

[ziggy]

Re: Fuel pump and carb questions

in yer pic of yer new pump.
the top one comes from the fuel tank.
the next one down, the threaded one, goes to the carb fuel inlet
the one on the bottom goes to the vent on the carb. via yer clear plastic tube.....

 

[achris]

Re: Fuel pump and carb questions

Yes. The hose from the top of the valve cover (and it's not a PCV valve, it's just a breather) goes to the flame arrestor. The clear fuel resistant hose goes to the barb at the top of the carb. Go to any hobby shop that deals with model aeroplanes. Ask for 'tygon' or 'silicone' tubing.

Chris.............

 

[Fishermark]

Re: Fuel pump and carb questions

Thanks! For the record, there is no provision in the flame arrestor for a hose to attach to. I can rig something of course. I note from Ziggy's picture above what seems to be a "fixture" that simply attaches to the flame arrestor. Here's picture of mine from the top:

There is no barb or fitting on the bottom. Is the fixture from Ziggy's available aftermarket?

 

[achris]

Re: Fuel pump and carb questions

There is no barb or fitting on the bottom. Is the fixture from Ziggy's available aftermarket?

No, it's factory and part of the flame arrestor. You may have an automotive valve cover. I would just make a fitting to put on the flame arrestor and be done with it.

Chris...........

 

[MikDee]

Re: Fuel pump and carb questions

No, it's factory and part of the flame arrestor. You may have an automotive valve cover. I would just make a fitting to put on the flame arrestor and be done with it.

Chris...........

Yes, the orig part on all the Merc engines I've had was just a piece of metal pipe mitre'd on the end, stuffed up against the flame arrestor, with a plate attached to it, riveted to the F.A.,,, By the way, everytime I took the F.A. off, the plate, pipe, & hose used to swing around on the F.A. like on a hinge,,,lol

Is there a hose barb for the fuel line, and for the clear hose (fuel pump safety) line? Or, does the clear hose go in the bottom of the carb on that big fitting? If the latter, I hope there's no strong manifold vacuum from the carb. at that fitting!