Primer bulb collapsing

[Merculator]

HI,
I am having a problem with the primer bulb collapsing on my 98 Merc outboard (3.0 Carb / 225HP) after running for a while the primer bulb collapses motor starves for gas and stalls - I can prime and run for a while then the gas runs out, the bulb firmness also changes (gets softer) as the RPM is increased. I have an in line water seperator (Filter/ bowl type) and the small factory in-line filter installed. I can blow thru the vent line and supply lines and there appears to be no blockage of either line.
Fuel pump? How do properly check it, is there a pressure value? If I disconnect the line coming out of the pump and bump the key I do get gas...thanks
T

[vnemous]

There should be a check valve in the fitting that goes to your fuel tank. I have had that get stuck and cause this problem Just a thought.

[coffeeguy]

I have the same problem with an early 225 merc. I only had the problem with the on board tank not extra 5 gallons portables. What I found was the fitting coming out of the tank(onboard) had a slightly smaller inner diameter then other fittings of the same size.I changed to a fitting with the larger internal diameter. I just put the boat in the water today but have not had a chance yet to try it but I think it was causing a enough of a restriction to cause it collapse. It generally did not collapse unless I ran 4500 + for a few minutes.If I saw it begin to collapse I brought the rpm down to 3600 or so and it filled back up. On the portable tanks the boat was 6200 for how ever long. I should know tomorrow if we get some half way decent weather.

[samari]

Check for a restriction in the fuel line, make shure the tank is venting. Check the priper itself to make shure it didn't come apart.

If you are running the grey mercury fuel line cut it back a little bit and make shure the inner liner is still attatched to the outer. IT will collaps and stop fuel flow.

[patchesII]

check for a restriction between the bulb and the tank. most common would probably be that anti-siphon valve that is no doubt in the fitting coming out of the tank. make sure your vent on the tank is still venting and it would also probably be a good idea to replace the bulb and fuel line with new stuff. there could also be a filter in your tank over the pickup tube that you need to check for debris. the fuel pump is doing just fine. it still has enough suction to flatten the bulb.

[coffeeguy]

Got out this morning . Running 5000 rpm and had no problems. I think the restriction was the fitting coming out of the tank to join the fuel line. >Made a few minor changes over winter so be a couple of days before a get it all out. Hope it gives you somewhere to look. P.S it was collapsing when pulling skiers at a lower rpm then regular running.

[patchesII]

pulling skiers is a pretty good extra load which adds to the fuel requirement quite a bit so it's not surprising for it to happen at a lower rpm

[Merculator]

Hi, First off Thanks guys for all the help with this!!
so far I checked the pickup tube in the tank and was able to completely remove it there was no anti siphon valve, or tube screen installed. A basic alum tube with a 90' barb connector. from there I checked the line to the inline water/sep/filter (cartdrige/bowl type) out to a 3/8 union to the bulb 'in' side. I found no restrictions, leaks, or seperation of the tube lining. I was able to blow air thru the supply line and into the tank and thru the vent line as well - so the tank seems to be venting. I replaced the bulb with a new 3/8 bulb and received the same result when running at high rpm. I believe the fuel pump is working correctly because it sucks the bulb flat. I still suspect the bulb check valve on the 'in' side of the bulb. but why would it keep getting stuck? I still need to run a 'red can' tank and maybe some clear fuel line would help with the diagnosis. I also bought a fuel pump rebuild kit so what the hell ill do that too..in addition to the water pressure relief valve which decided to go sometime between test runs. 'why is there water leaking from the side of the block?'...
always something. BOAT$
thanks again.
T

[capnzee]

are you sure you have the fuel line (bulb) installed with the arrows going in the right direction? I know, dumber things have happened, ???:thumbsup:

[donmac]

check for bottle foil seal in bottom of tank.

[Merculator]

OK! I think i finally solved my primer bulb problem! After checking all the obvious, changing the lines, using an alternate tank, and process of elimination, I confirmed that I was indeed picking up debris from the bottom of the tank. So, I ran a line direct from the tank to the bulb w/ an inline filter and bypassed my water seperator - I would run the motor until the bulb started going flat then stopped the boat and immediately pulled the pick up tube out of the tank. When I blew through the tube I had some clear gummie silicone like crap come out of the tube. in some cases it was like a ball in others it was stringy - I pulled out one string that was about 6 inches in length. I did this about a dozen times - I was thinking it may be old silicone that was used to seal the fuel sending unit that somehow was dropped into the tank. but NOW! i am hearing this could be due to the gas we get these days breaking down or by mixing E10 fuel (10% ethanol fuel) with gas that has MTBE (methyl tertiary-butyl ether) as an additive. 'they' now say the fuel we buy is good for about 90 days before it starts to seperate and degrade.

Anyone have any experience with this?

Have an effective method for flushing out your fuel tank and removing debris from the tank w/o taking the tank out of the boat??

Anyone ever use a shop vac? I don't know - sounds dangerous...:reddevil:

Thanks again guys for all the help:cheers:

[tux974]

Had a similar problem. Found that an after market bulb was bad. Installed a new Merc just need to make sure the bulb says Quicksilver on it and it seems to have solved the problem.

[coffeeguy]

There are two inner diameters for the 90degree fitting coming from the tank. My original had a smaller dia aand the new one is larger. It has solved my primer bulb problem.

[coslanzetta]

do not use a shop vac...has an electric motor,as soon as u hit the on button,it will turn into a blow torch...the fumes will hit the electric motor immediately,,,,not a good idea...

[sl!ck]

They make a venturi style pump that works on air from a compressor that makes a suction on the line thats the safest way other than a large diameter siphon.

[CharlieB]

try this it sounds stupid but it does the job. Go to a store that sells waterbeds
they sell a drain kit that works like the post above mentioned. only with water. I use
an air compressor instead of water with it and it works great for getting crap out of tanks and its safe.

[perthcatboy]

I have the exact same problem on one of my Scarab's 200hp Yamaha 2 stroke's, always the portside motor, I have tried replacing the fuel/water sepaerater filter, all new fuel hose, new primer bulb, and have siphoned all 350 litres of fuel out of the tank, I had alot of that white jelly (jello) stringy stuff come out of the tank, I guess I will try and find a larger diameter fuel tank pickup, same as you guys, it runs perfectly when I bypass the fuel primer and filter and run a 25 litre tank directly to the outboard with its own fuel line.
Interestingly the starboard motor hasnt had any of the same problems!
perhaps it has a different pickup in the fuel tank?
Do you guys in the USA have any fuel conditioning product for getting rid of the white stuff that comes from the ethanol blend fuel? or to stop it from degrading in the first place?

cheers
from Western Australia

[capnzee]

You must have a restriction within the tank at the pick-up or (if you are feeding just one engine) your air inlet may be plugged. If your tank is feeding two engines and one engine is not effected, while the other is collapsing the fuel primer bulb, your air inlet (overflow) is open and your fuel pick-up inside the tank is plugged. This pick-up often has a screen "sock" or filter and it usually quite easily removed from the tank. That white stuff you are finding in the tank could be causing the problem at either end, you may solve your problem by adding stabilizer to your fuel. We get stabilizer at any auto supply store and add it to the fuel when the engines are not going to be run for an extended time eg. 3 months--I think Mercury outboard states that today's fuel begins deteriorating in around a month or so. :cheers: Rod

[perthcatboy]

Thanks for that, the boat tank does feed both motors, but through seperate pickups, I will check the pick-up for the port motor.
Whats the 'air inlet (overflow)'? is it the filler breather for the fuel tank?
(The yamahas are not oil injected, I mix the oil in the fuel tank.)
The boat came from the USA, via Singapore for a year, so perhaps this is where the white stringy jelly ethanol stuff came from? As Australia is yet to start using ethanol blended fuel.

[capnzee]

Thanks for that, the boat tank does feed both motors, but through seperate pickups, I will check the pick-up for the port motor.
Whats the 'air inlet (overflow)'? is it the filler breather for the fuel tank?
(The yamahas are not oil injected, I mix the oil in the fuel tank.)
The boat came from the USA, via Singapore for a year, so perhaps this is where the white stringy jelly ethanol stuff came from? As Australia is yet to start using ethanol blended fuel. The air inlet (overflow) acts to let air out of the tank when filling and allows air back into the tank as the fuel flows out in order to prevent a vacuum or vapor lock. You could also switch the pick-ups and see if the problem jumps to the other engine. :) Rod

[Capt.Insane-o]

Pre mixed fuel will last "longer" (relative term) and the additive I have had the best luck with is the new marine formula Sta-bil. In my own ways of testing, gas stays "good" (again relative term) for 7-10 days in a boat up here during season without an additive. I get my gas for my non race fuel motors at the airport or at the state dock, which in Michigan all state docks are required by contract to carry ethanol free fuel. Remember guys it is not only the fuel line to the engine it eats up, but also the filler and vent lines.