Water in Fuel/carb causing lean condition?

[Martin Brody]

Sorry if this has been covered but I was having issues finding the exact condition. I did not want to confuse it with another condition. Here is the details:

Mercruiser 4.3l v6(1995)

Just started happening in the middle of cruising.

Motor revs past 2k fine with no load(idle).
Under load as you are moving the throttle forward slowly you reach a point(1800 rpms) where instead of the motor getting louder/rising rpm, you actually feel a slight drop in power and if you keep going the engine will blowback through carb and then drop back rpms. I cannot get on a plane with this condition,but I can go slow all day long.

What I have read is possible water in fuel/carb causing lean condition that under load(needed fuel condition)would blow back. Also the jets or float in the carb but water issues seem to cause immediate symptoms.

Timing is fine 8 btdc at idle(did not do wire jumper/no advance timing test yet), compression is fine,fuel is questionable but should be fine(filled 6 months but had older fuel in her for a while).lots of fuel stablizing and gallon of xylene and mystery oil for good measure, fuel/water seperator 4 months old and only used 2 times.

Anyone have experience with this loss of power blowback condition based on lean condition.

 

[FreeBeeTony]

Re: Water in Fuel/carb causing lean condition?

Try this......courtesy of Don S:

If the filter had a lot of water in it, and there is water in the carb, then it won't run thru the carb as easy as the gas. Might have to use the ole "let the engine suck the garbage out of the carb" tick a couple of times.
On muffs (or in the water, doesn't matter) (drive down and steering straight to keep everybody happy) . Now, disconnect the throttle linkage, rev the engine up, when it gets up to 3 to 4K Close the choke plate completely (don't allow the 4bbl to open) and at the same time open the throttle to WOT. THe engine should start dying. Just before it does, open the choke, and let the engine gain rpm again. Do this a couple of times.
Usually sucks any dirt, and water out of the carb.
But you need to do that after you are sure the filter is getting only gas.

He suggested this to me about 2 yrs ago....worked for me!

 

[Bondo]

Re: Water in Fuel/carb causing lean condition?

fuel/water seperator 4 months old and only used 2 times.

Ayuh,... So have you Checked the filter yet,..??

1 minute, the 1st time is Too long if there's Water in it....

 

[Martin Brody]

Re: Water in Fuel/carb causing lean condition?

Thanks for the info.


Will check/try all and post back. I was thinking of getting one of those fuel water separators that has the purge on the bottom for water. I guess I will read some reviews on how good/long those things work for and if they are worth the money.

 

[Bondo]

Re: Water in Fuel/carb causing lean condition?

I was thinking of getting one of those fuel water separators that has the purge on the bottom for water.

Ayuh,... It's yet another place for Gas to leak into the Bilge,.... BOOM...

If you have a Water Problem,... Fix the Problem, instead of heading it off at a pass...
There's No reason for water in the gas, under normal conditions..

 

[Martin Brody]

Re: Water in Fuel/carb causing lean condition?

Fuel is clean. No water, let sit in jar overnight. I got the fuel from the filter, filter looks good(not exactly sure what I'm looking for). I also inspected the tank and there were no water or varnish deposits separated from the fuel at the bottom. All my new plugs are fouled though already, 3 hours of use. Oil fouled is what it looks like to me. Strange thing is the compression is good in all cylinders. Every plug is identically fouled.I will check the carb in detail next.

 

[grahamh]

Re: Water in Fuel/carb causing lean condition?

It sounds to me like a simple carb problem, sounds like you have a clogged jet or something.

Try the hand-over-the-carb (or with the choke plate) and see if it works, I've had it work for me before, but I've also had it not work.

If it doesn't work, it's probably time to take the carb apart and clean everything, blow the jets out with compressed air or carb cleaner. I've cleaned carbs and put them back together without rebuilding them, and sometimes it fixes the problem, but as long as you're in there, it kind of makes sense to rebuild it anyway.

 

[Fishing56]

Re: Water in Fuel/carb causing lean condition?

Just a thought, check your flame arrestor/air filter and make sure it is not clogged. Happened to me once.

Fishing56

 

[ENSIGN]

Re: Water in Fuel/carb causing lean condition?

That plug looks like it's running to rich,check to be sure the choke opens all the way.Could also be a leaky needle valve & seat

 

[JustJason]

Re: Water in Fuel/carb causing lean condition?

I have the mity vac, it's been through at least 150 oil changes with no problems. I don't use the hoses that come with it though, I made up my own.

If anybody has a lathe would they mind makeing me something?