# Primer Bulb



## Gramps50 (Mar 1, 2012)

Went to the boat store to get a primer bulb and some hose for the used old stye metal tank that I bought. The parts guy at the boat store told me that the primer bulb should be vertical so the check valve will work properly. I want to put the new tank in the back of the boat by the motor, bad idea another story. I got some like and a new motor fitting and put the tank in the back. I put the primer bulb about a ft from the motor and it was basicly vertical. The motor ran really well, it would idle for ever. In fact it idled the whole time I went and parked the truck, wouldn't do that before with the plastic tank up in the front compartment. The primer bulb in that case is a ft or so from the tank and lays on the compartment floor.

I am going to put the metal tank up in the compartment where the other tank was a the boat works better with the weight up there. My question is will the bulb still work if I hang it off the engine in a vertical orientation? 

The fuel line that i bought 5' is the USCG approve stuff. What is run from the storage compartment to the motor looks like regular automotive fuel line, is this alright to use?


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## lckstckn2smknbrls (Mar 1, 2012)

I'm using 14' of 3/8" automotive fuel line.


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## crazymanme2 (Mar 2, 2012)

> I'm using 14' of 3/8" automotive fuel line.



+1 =D> 

I've had the auto fuel hose in my boat for 5 years.


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## cajuncook1 (Mar 2, 2012)

The purpose of the primer bulb is only to pump fuel to the fuel pump and carburetor, so the engine can start. After the motor is started, then the fuel pump gets pressure pulses from the motor to siphon fuel from the tank and forward it to the carburetor to maintain an adequate supply of fuel at various running settings from idle to wide open throttle(wot).

So, what I am saying is that the primer bulb does not effect your motor idle and running condition after it is started. Now, if the bulb is put on backward then yes it can effect flow to the motor. Most primer bulbs have some kind of arrow or marker to indicate the direction of flow of fuel.

So, it does not matter where you put the bulb along the fuel line, just as long as the arrow or fuel flow path of the bulb is pointing toward the motor. *The primer bulb does not have to be vertical to work. * 

As to why your motor idles better with the bulb closer to the motor...dunno. It may be the fact that the new hose, tank, and connections prevent air from entering the system and allowing better fuel delivery and better fuel pump function. The fuel pump pumps liquid fuel well, but horrible with excessive air due to fact the air will displace the fuel in the pump.

Any way, glad to hear your motor is running better!! Tight lines, the feel of the thump and a cold beer with fish chips is what it is all about! :LOL2: :LOL2:


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## Pappy (Mar 2, 2012)

What Cajun says is absolutely correct. The parts guy was correct also to a certain extent. The check valves will work better when the primer bulb is vertical but only when you are pumping the bulb is that desirable and only if the valves are sticky. Otherwise not needed. 
Once you have filled the fuel bowl in the carburetor with fuel the primer bulb has absolutely zero to do with running quality as the engine fuel pump now has taken over the job of keeping the fuel bowl full. Note .... there's only one M in primer!


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## nomowork (Mar 2, 2012)

I've read some articles and posts about the primer bulb positioning also. I've had my share of primer bulb failures so now position them near the motor in a vertical manner. One advantage is that it keeps it off of the floor.


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## fender66 (Mar 2, 2012)

IMHO, the more common problem with primer bulb/fuel lines are that they aren't sealed properly and/or have cracks. When they suck air...that will effect the way an engine runs.


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## Gramps50 (Mar 2, 2012)

Pappy said:


> What Cajun says is absolutely correct. The parts guy was correct also to a certain extent. The check valves will work better when the primer bulb is vertical but only when you are pumping the bulb is that desirable and only if the valves are sticky. Otherwise not needed.
> Once you have filled the fuel bowl in the carburetor with fuel the primer bulb has absolutely zero to do with running quality as the engine fuel pump now has taken over the job of keeping the fuel bowl full. Note .... there's only one M in primer!



I need spell check, thanks Pappy, corrected.

I am inclined to think that the plastic tank was causing the fule pump to suck air. I'm going to put the metal tank up front, so then we'll see what happens. The plastic tank has a 360 degree swivel and I think it is the source of air leak. if it't not tightened down correctly then the bulb won't ever pump up.


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## cajuncook1 (Mar 3, 2012)

Your tank does not need to be air tight. In fact most plastic tanks have an air vent screw that is loosen to allow air into the tank. The fuel pump siphons fuel from the pick up tube at the the bottom of the tank and pumps it to the carburetor bowl. If the tank would be air tight then it would soon create negative pressure and the plastic tank would start caving in on itself. Sounds familiar to all of us, because a one time or another we have all forgotten to loosen the vent cap on the tank and the engine starts running poorly. The fuel pump can only suction so much out of a tank with negative pressure....then when we crack open the vent screw or open the tank cap and suck in a bunch of air in the tank and returns normal condition in the tank....lol 

The issue with air entering the fuel system comes from poor or damaged seals in the connectors, or cracks in the fuel hose from the tank to the motor or internal fuel hoses going from the motors connector to the fuel pump or from hose going to the fuel pump to carburetor bowl.

So, when you got new hoses and new primer bulb for the metal tank you possibly eliminated the air enter the fuel system from the old hoses, connectors, or older primer bulb. The older metal tanks (non pressured tanks) has a valve that allows air enter the tanks without the tank leaking fuel. The newer plastic tanks have to be manually vented with the vent screw.


Hope this helps.


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## Gramps50 (Mar 3, 2012)

The bulb and line for the plastic tank were new and purchased and installed just before I bought the boat, including the gas tank. The problem with the tank is the pickup is 2 piece, there is one piece in the tank and then the swivial on the outside that when tightened down seals with an o-ring, this is where I believe it sucks air. The directions say to tighten it hand tight and then an additional 3/4 turn. This won't happen without cracking somethings. In my opinion it's a poor design, the theory is good, but it ends there. Here's the tank I'm talking about, mine is the 6 gallon model.

I'm going to plum the metal tank in up front and see how it goes.


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## cajuncook1 (Mar 3, 2012)

I have both the metal and the plastic tanks. Both work fine for me, but I am partial to the metal tank!! 8)


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## Gramps50 (Mar 20, 2012)

My motor ran the best when the metal tank was in tha back and the line was ony 5' long. The problem with that location is that I did't like the way the boat handed. Hard to explain it just had a squirrely feeling.

Moved the tank back up front and got rid of the automotive gas line running down the side of the boat. Replace it with coated steel gas line with rubber on the tank end and the motor end. Still has issues, sometimes all was fine other time the motor would die. With this configuration it would never idle down right if you turned it much slower than start it would die. Wheh I did the hard line I miscaculated the length of the fuel link going to the motor. I didn't take into account turning the motor to steer.  

The last time I was out the motor died and I never got it to start again, had to use the trolling motor get get back to the ramp.  This is partically what prompted the rewire of the motor.

Got more fuel line so I could turn the motor to steer. Today I put the motor back on the boat and started plumbing the fuel line. While checking it to make sure I had enough length for a turn I discovered that the quick disconnect fitting was loose. A light bulb went off in my head. When the motor ran and idled so well it had the new quick disconnect that I purchased. I went and got it and sure enough it was a lot tighted than the other one. The old one was all cast alumiumn then new one from the Mercury store had a brass insert. I put the new one on and started the motor and it ran like a champ. It would idle way down. 

So I took the brass fittings out of the old one and pitched it in the trash. Can't believe all the issues it has caused.


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## nomowork (Mar 21, 2012)

When I purchased a "new to me" 40hp Mercury, I found out that the quick disconnects for the Mercury were different at the tank end and at the motor end. ??????????????????


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## Gramps50 (Mar 21, 2012)

on mine the tank end is a male piece and the motor end is a female peice. Unless they have been changes the 2 connectors should plug into eachother too. I had to replace the one on the motor. The tank end was new as the plastic tank that came with the boat and motor had the new style 2 pin connector on it.


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## bassin4fun (Mar 21, 2012)

Have also heard that a smaller dia. hose will pull fuel better if there is a longer fuel line such as your application.....????


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