84 Merc 25XD primer bulb going soft at high speed engine stalls

[PeteB_2000]

Hiya,

Had my boat out on the river today engine seems to be running a treat now only problem is at the top 3rd throttle the only way to keep going is to keep pumping the primer bulb if i dont it stalls as
it dont seem to be getting enough juice to it otherwise, any ideas
what I should do to sort this niggly problem out?

Best Regards
Pete

 

[JUSTINTIME]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

sounds like a hole in the fuel line or time to rebuild the carbs

 

[Barnacle_Bill]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

Check all your fuel lines and especially the primer bulb. All should be soft and pliable with no cracks. You could also have pinholes in the fuel pump diaphram. They are easy and cheap to rebuild.

 

[PeteB_2000]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

hiya guys,

thanks once again for your expertise, I think the carbs ok so I will probably replace the fuel line and bulb from the tank to the engine.

Cheers
Pete

 

[Texasmark]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls


well I have a different idea. A soft bulb says that the fuel supply can't keep up with the demand. If it were the other things, the bulb would be tight and the engine wouldn't want to run.

Your fuel pump is "sucking a vacuum" on your fuel supply due to a restriction somewhere.....either in or downstream of the bulb......toward (and including) the tank.......not toward the engine.

Did you open your fuel vent on your tank? Maybe your pickup screen in the tank is clogged. Maybe the check valve in the squeeze bulg is defective (stuck closed).

To check my fuel flow I use a popsickle stick, trim it to fit the ball in the connector, depress and hold the ball and squeeze the bulb as fast as I can. If I get a good flow fine. If not, I go a looking.

One thing that can cause problems is if you put a fuel stabilizer in your tank (with water in the tank) or if you are burning ethanol and had water in your tank. Alcohol mixes with water and makes a white (milky) gooey blob that can clog your screen or your fuel line. BTDT

Mark

 

[PeteB_2000]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

thanks for the advice, I changed the fuel filter to a inline filter the type used by mini moto x bikes I also changed the fuel line and bulb to another that I have I also used thread tape on all connections and cable tied all the ends to make sure all connections very tight.
Took my boat on the river today and it was even worse....!!!, its like it runs till the fuel thats been primed has gone and then it stalls, I then dropped anchor and changed the fuel filter back to the original filter, off I went again but just the same runs till fuel thats been primed has been used up then cuts out......
Argghhhhhh can anyone help please

Mr Jinxed

 

[Smig]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

Like Mark said - Could it be the fuel bulb itself? I had one that kept going soft so I replaced the bulb - problem went away.

 

[Plainsman]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

My vote is for fuel pump... in my non-expert opinon

 

[PeteB_2000]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

the bulb has been swopped so possibly its the fuel pump would a
rebuild kit sort it or would i need a new one?

 

[Silvertip]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

Primer bulbs during normal operation will go soft but should not be sucked flat. Fuel is being drawn through the bulb -- not forced -- so it stands to reason it will not stay firm once the engine is running. Since you already found out that's not the problem, and you also determined that squeezing the bulb allows the engine to run, you more than likely need a fuel pump rebuild.

 

[alana]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

thanks for the advice, I changed the fuel filter to a inline filter the type used by mini moto x bikes I also changed the fuel line and bulb to another that I have I also used thread tape on all connections and cable tied all the ends to make sure all connections very tight.
Took my boat on the river today and it was even worse....!!!, its like it runs till the fuel thats been primed has gone and then it stalls, I then dropped anchor and changed the fuel filter back to the original filter, off I went again but just the same runs till fuel thats been primed has been used up then cuts out......
Argghhhhhh can anyone help please

Mr Jinxed

 

[alana]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

are you sure that inline filter will let enough fuel through for your motor

 

[PeteB_2000]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

ive swopped the fuel filter back to the original fuel filter, is anyone in the UK who can recommend a marine place for a carb
and fuel pump rebuild kit?

Back out on the river again today it was 27C today in the UK its an indian summer in October....!

Having to keep my hand or foot on the bulb and keep squashing it is a real pain in the butt
Pete

 

[PeteB_2000]

Re: 84 Merc 25XD primer bulb going soft at high speed engine stalls

i found my local dealer today about 20 miles away, phoned up and asked how much for fuel/carb gasket/diaphram kit etc going to be about 40 pounds, so he said he would have a look and try find fault, so i took it over will update when i get to know how much and what it is

Pete