hesitation on 3.0L merc

[jafo9]

i've developed a slight hesitation on my 3.0L I/O Mercruiser in my pontoon boat. at pretty much any throttle over 3K it will "hesitate" for a second and then proceed. It's like you pull the throttle back and quickly push it back forward. It happened a few times on the lake today and then it got harder to replicate. From reading the manual and the service manual, it sounds like i need to get into the fuel/water separator and the filter. My first question is: are there any tricks to getting it off? last thing i want is to drop a bunch of small parts in the bilge. mine doesn't have a real screw on filter, it's got the one that is built into the fuel pump. its an '05 carberated model. the service manual wasn't real clear on how to get into it. does it have to come out completely, or can you drain the water and check the filter while mounted to the motor?

thanks for the help, and any suggestions would be appreciated.

 

[towman818181]

Re: hesitation on 3.0L merc

sounds like the accelerator pump in your carb is the issue

 

[jafo9]

Re: hesitation on 3.0L merc

i thought an accelerator pump only put out gas on acceleration? does it flow continuously?

 

[fat fanny]

Re: hesitation on 3.0L merc

I had the same issue w/ my 96 3.0 and it's common. The only solution is to rebuild and or check you are getting sufficient fuel pressure all filters are clean and to make sure you didn't get some bad fuel but most likely it's the carb rebuild it and it will most likely solve your issue try after market marine .com they carry the universal kit for all mercarbs and ones for rochesters 35.99 +s/h. I had all but 50.00 counting carb soak wrapped up in my job boat runs better than ever.

 

[jafo9]

Re: hesitation on 3.0L merc

had some other problems. ended up having to replace the starter and the 90amp fuse on the starter solenoid. the only thing i was able to do in my attempt to track down the hesitation was to open the drain valve to let water out of the fuel pump. ran fine all day saturday after the starter marathon on friday.

i would still love to know how to get to the fuel filter inside the fuel pump. do you just take the water drain all the way out? how does the bowl come off? i bought a rebuild kit at west marine which came with a new filter and gaskets. i just need to know how to get the bottom of the fuel pump off? any help would be greatly appreciated.

 

[ken_23434]

Re: hesitation on 3.0L merc

I am not sure what you are referring to as the water drain on the pump, my 3.0 doesn't have one (am I missing something?).

Anyways, I have 1 type of pump installed on my boat and the other one inside a cabinet off a donor motor. I only thought the 3.0 had 2 different types of pumps avail (high volume and low volume).

But, on both of the ones I have, there is a bolt (about 5/16" or so) centered on the cap of the fuel pump (one design pump this is on the top, on the other it's on the bottom). If you loosen this bolt, it will release the pressure applied to a "cap" on the fuel pump. That cap is held in place with a metal strap that hooks at each side of the fuel pump body. Once the bolt in the center is loosened enough, you can tilt that strap one one side and then unlatch the "T" shaped piece of the strap from the fuel pump body. Then do the same for the other side. You should now see the fuel filter.

 

[jafo9]

Re: hesitation on 3.0L merc

i just have the one with the filter on the bottom of the pump. the manual refers to this a a fuel/water separator. not much of one, but i guess it could be in theory. i'll try to loosen the center bolt some more and get those straps off. i didn't want to take off too much and have the whole thing fall in the bilge. it a real bear to get stuff out after it falls.

 

[ken_23434]

Re: hesitation on 3.0L merc

You don't need to take the bolt out completely. I think the nut is retained in the strap. Once you pop the cap off the pump, the only thing in there is the filter and I think a spring along with the gasket. If the filter comes out, it should just be in the cap when you take it off.

Oh, some fuel will likely spill out too. Might want a rag or pan underneath to catch it if you are concerned.