1998 Mercury 150 loosing gas line primer bulb pressure

Joseignacio

Seaman
Joined
Jul 30, 2009
Messages
57
I have a 1998 Offshore Mercury 150. The outboard lost power and the primer buld was not hard. On one accasion, the engine almost turned off but I primed the line again making the primer bulb hard and the engine came back alive. It was as if the line is loosing pressure. The problem happened about three consecutive times and then it did not happen again. I am afraid something is about to happen ...........
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: 1998 Mercury 150 loosing gas line primer bulb pressure

I have a 1998 Offshore Mercury 150. The outboard lost power and the primer buld was not hard. On one accasion, the engine almost turned off but I primed the line again making the primer bulb hard and the engine came back alive. It was as if the line is loosing pressure. The problem happened about three consecutive times and then it did not happen again. I am afraid something is about to happen ...........

What's about to happen is burning down the power head. They do not like to run lean. They get too hot and the pistons melt.

It's normal for the primer bulb to not be real hard when it's running. After all, you are sucking fuel through it with the fuel pump in the engine.

Either the fuel pump is failing, or a fuel filter is plugging, or there is a restriction or air leak somewhere.

hope it helps
John
 

Really Old Guy

Petty Officer 3rd Class
Joined
Sep 1, 2009
Messages
84
Re: 1998 Mercury 150 loosing gas line primer bulb pressure

10 year old gas line, needs replacing. It could be an air leak.
Those zip ties should be replaced with stainless hose clamps
and check your fuel lines in the carb area. while putting gentle
pressure on the bulb.
Hope you find it soon!
Guy:)
 

"G"

Petty Officer 2nd Class
Joined
May 2, 2009
Messages
150
Re: 1998 Mercury 150 loosing gas line primer bulb pressure

You might check the in line fuel check valve (usually found on top of the tank) too. If that isn't doing it's job you'll loose suction. It's the same as an air leak so look for both. Gas line parts are cheap compared to powerheads.
 

Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,235
Re: 1998 Mercury 150 loosing gas line primer bulb pressure

All of the above and rebuild your pulse fuel pump. Its cheap and you will have all tha fuel issues covered (at least ta tha carbs and/or efi).
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: 1998 Mercury 150 loosing gas line primer bulb pressure

All of the above and rebuild your pulse fuel pump. Its cheap and you will have all tha fuel issues covered (at least ta tha carbs and/or efi).

A sleeper here. If the pulse hose has gotten soft, or leaking, the pump will be weak.
Ask me how I know. (Tygon hose)

John
 

hkeiner

Lieutenant Junior Grade
Joined
Oct 17, 2006
Messages
1,055
Re: 1998 Mercury 150 loosing gas line primer bulb pressure

In my opinion, systematic diagnosis is a good way to go. As previously mentioned, fuel starvation is not something you want to delay solving. Randomly trying various possible fixes on only a hunch can delay solving the problem.

The below linked troubleshooting guide may help you find the exact problem quickly. Alternatively, hooking up a portable fuel tank directly to the fuel pump, to see if the problem goes away, is another way to narrow down the problem. If the problem does not go away with the portable tank, the fuel pump is most suspect. If the problem does go away, a fuel line restriction or air leak is suspect.

http://forums.iboats.com/attachment.php?attachmentid=26607&d=1240244928

http://forums.iboats.com/attachment.php?attachmentid=26608&d=1240244937

http://forums.iboats.com/attachment.php?attachmentid=26609&d=1240244945

http://forums.iboats.com/attachment.php?attachmentid=26610&d=1240245079
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: 1998 Mercury 150 loosing gas line primer bulb pressure

When I shot a similar problem out of my XR4, I wound up hooking up a fuel pressure gauge. When the symptoms occurred, the gauge would go way low to near 0 psi. 2 lbs seemed to run it fine. (carbs, of course)

There were 6 or more seperate items all contributing to the poor fuel delivery. I knew it for sure when I found them all.

hope it helps
John
 

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: 1998 Mercury 150 loosing gas line primer bulb pressure

All excellent comments. I did several this past year where ethanol-bearing fuels were a major contributor.

Merc has issued several TSB's on fuel starvation, with some of the problems due to deterioration from ethanol-fuels, but from other issues also.

Here's a link to the .pdf file for the current (as far as I know) fuel starvation TSB:

http://dc151.4shared.com/download/101684956/9767ea93/2001-17_Fuel_Starvation.pdf

HTH & G'luck with the troubleshooting.........ed
 
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