The Hull Truth - Boating and Fishing Forum

Go Back   The Hull Truth - Boating and Fishing Forum > BOATING FORUMS > The Boating Forum
Search

Notices

Random Quote: Fishing is not a matter of life or death.......Its much more important than that!!!!
Closed Thread
 
Thread Tools Search this Thread
Old 06-02-2004, 09:15 PM
  #1    
Junior Member
 
Join Date: May 2004
Location: Bradenton, FL
Posts: 28
Default Fuel/Water Separator-How's it work?

Can anyone explain how the separator works on my new mercruiser? I'm wondering if it's causing my sputtering & stalling problem once the boat is warmed up and under load at cruise. Doesn't happen at lower loads, and never happened until recently.

Thanks...
__________________
Sincerely,
Michael...
Bradenton, Florida
Knot2shy is offline  
Old 06-02-2004, 09:21 PM
  #2    
Senior MemberCaptains Club Member
 
Join Date: Nov 2003
Location: Longs, SC
Posts: 2,555
Default RE: Fuel/Water Separator-How's it work?

Did you just add the fuel/water separator? My dealer told me that Mercury frowns on adding a fuel/water separator in that it will cause your engine to run lean. I had added one and they readjusted the fuel mixture for me on my 20 hour service last year. It could be the cause of your problem (according to my dealer) especially if it started occurring after you installed it.
mole2 is offline  
 
Old 06-02-2004, 09:24 PM
  #3    
Senior MemberCaptains Club Member
 
Join Date: Dec 2002
Location: Orlando
Posts: 3,997
Default RE: Fuel/Water Separator-How's it work?

It works by gravity.

The water is heavier than the gas, so it will drop to the bottom of the filter, and collect there. Get enough water in it, and it will eventually start getting sucked in the carbs or injectors.

Pull the filter and dump it's contents into a tupperware bowl. If it has water in it it will be easy to see. It will be the clear stuff you know like water?
Sea_Dad is offline  
Old 06-02-2004, 09:25 PM
  #4    
Senior MemberCaptains Club Member
 
Join Date: Aug 2002
Location: St. Augustine, Fl
Posts: 14,459
Default RE: Fuel/Water Separator-How's it work?

Michael,
The separator works by the fuel being sucked thru a filter cleaning out any debris. The separator also allows water to pool at the bottom of the separator. If your separator is full of water it can cause your engine to stall or studder, particularily at a higher speed. You can unscrew it and pour out the contents into a bucket and look at it. Fuel and water will separate whne the contents settle.
__________________
Since 1988. Proudly serving my community and state.

Cracker is offline  
Old 06-02-2004, 09:26 PM
  #5    
Junior Member
 
Join Date: May 2004
Location: Bradenton, FL
Posts: 28
Default RE: Fuel/Water Separator-How's it work?

Thankss Mole2. Nope, this was a complete merc repower package, complete with separator. It's a 5.7 liter 250hp 2bbl carb unit. Put it in 1 year ago, no probs initially, just started about a month ago, intermittent, but getting worse. I'm going to pull the canister on the separator, but not sure what to expect. No details in the service manual. I'm trying to troubleshoot, and not really sure how they work. Is it possible for the filter to fill up and water to not be removed and go to the engine causing the problem? If so, why only at load?

Also, does the cannister have to be replaced regularly? It looks like an oil filter, about the same size?

Thanks.
__________________
Sincerely,
Michael...
Bradenton, Florida
Knot2shy is offline  
Old 06-02-2004, 09:35 PM
  #6    
Junior Member
 
Join Date: May 2004
Location: Bradenton, FL
Posts: 28
Default RE: Fuel/Water Separator-How's it work?

Thanks gents...

Anxious to get to it tomorrow pm and check it out. I'm inclined to replace the filter, and replace the inline fuel filter in the carb housing as well. They're a year old. I just saw a recommendation in a merc manual to replace once a year. Likely a good investment.

Thanks again!
__________________
Sincerely,
Michael...
Bradenton, Florida
Knot2shy is offline  
Old 06-02-2004, 09:36 PM
  #7    
Senior MemberCaptains Club Member
 
Join Date: Aug 2002
Location: St. Augustine, Fl
Posts: 14,459
Default RE: Fuel/Water Separator-How's it work?

Michael,
Yes the seperator should be replaced periodically at least yearly if not twice a year. It is not a complicated piece of equipement. It is not an oil filter. Be sure to replace it with a seperator. Also there are two types of filters. One with a small hole in the top center the other is an omc with a larger hole in the top center. Since you have a merc refit it will most likely be the smaller hole but you never know. The size differences are obvious. Good Luck.
__________________
Since 1988. Proudly serving my community and state.

Cracker is offline  
Old 06-03-2004, 07:55 AM
  #8    
Senior MemberCaptains Club Member
 
Join Date: Feb 2001
Location: West Virginia
Posts: 3,877
Default RE: Fuel/Water Separator-How's it work?

Real quick and easy.

Water and gas will not mix and water is heavier than gas. So gas will always 'float' on top of water.

The seperator is really two devices in one, it separates fuel from water and it filters the fuel. It can and will also filter water, if it gets the chance. If you were to cut your sepearator in half up and down to get a look at it all it would look a lot like a roll of toilet paper sitting on top of a coffee cup. Water enters the seperator down the middle and drops down the hole in the center of the filter - the part that looks like a roll of toilet paper. The cup is at the bottom and any water in the fuel finds it way to the bottom, because its heavier, and stays there. As the calister fills up the water remains at the bottom and the filter element fills with the gas that is floating on top of the water. The gas passes through the filter element, which captures particles, and exits on the outside of the element, the outside of the part that looks like the roll of paper. After the fuel passes through the filter element it is channeled back to the top where it is passed to the outlet port. So all of the water is captured in the bottom and the fuel rises inside the element, passes through the filtering medium, and then exits to a fitting that goes on to the engine. Obviously passing fuel throgh a filter imposes some restriction to its flow, but not much unless the filter is operating at 100% efficiency (is completely jammed up). The problem is that the water in the bottom isn't going anywhere and sooner or later it will fill up the bowl at the bottom (or simply an empty chamber inthe bottom if its a one-piece filter element) and then water will be up at a level that allows it to pass through the filter element. If that happens the filter will be more than happy to let water pass through to the engine. Keep that in mind, because a lot of folks don't understand it and will tell you wrong - a fuel seperator/filter will be more than happy to allow water to get to your engine if that bowl fills up. When this happens there might be a little bit of sputtering for about 10 seconds, and then the engine will simply die. This, a water-filled seperator, is not something that will happen intermitently for a couple of outings, it will kill the engine in a hurry. Fortunately it really doesn't do any harm, and in fact it will clean your plugs like they have never been cleaned before (water makes a great decarb juice) and all you have to do is dump the chamber, pump it full of agas again, and get the engine restarted to go on your way. The best way to treat all of this is to simply put a valve on the bottom of the bowl. We did that years ago to both of our Racors and I drain some fuel (with its water) before and after every single trip. I keep a small glass in the boat just for that purpose. You can spot water in the gas instantly in a glass, and you'd have to be blind to miss it, there is absoltuly no question at all if the stuff is in there.

Thom
Thom is offline  
Old 06-03-2004, 09:28 AM
  #9    
Senior MemberCaptains Club Member
 
Join Date: Jun 2001
Location: Boynton Beach Fl (Pursuit
Posts: 5,541
Default RE: Fuel/Water Separator-How's it work?

Thom, haven't seen you for awhile! How did the repower go?
KevinM is offline  
Old 06-03-2004, 09:51 AM
  #10    
Senior MemberCaptains Club Member
 
Join Date: Nov 2002
Location:
Posts: 111
Default RE: Fuel/Water Separator-How's it work?

uh, Thom. Not sure what type of filter you are describing but I am looking at the head of a Racor as I type. The fuel enters the head and goes to the outside of the filter. From there is passes through the filter and exits from the inside of the filter up to a threaded port on the filter head and from there a transfer tube passes it from the middle of the head to the exit port. If you look at the drain valve on the Racor bowl you will see that it is located on the outside of the bowl not the middle of the bowl. The middle of the bowl, which is an extra chamber, does not appear to me to be drainable via the valve. It can only be drained when the bowl is removed. I am guessing here but it seems to be a reservoir for any water that ever passes through the filter. After passing through the filter it seems to settle by gravity to the inner chamber. Capeche?
marinerman is offline  
Old 06-03-2004, 04:10 PM
  #11    
Senior MemberCaptains Club Member
 
Join Date: Feb 2001
Location: West Virginia
Posts: 3,877
Default RE: Fuel/Water Separator-How's it work?

Sorry, must have got the pathway wrong, but the bottom line is that the water settles in the bowl but if its full the water will happily pass through the filter and go on to the engine. The little ball valves I have in the bottom of each of my Racors goes in where the brass plug used to be (I use the metal bowl types), which is on the outside ring of the bowl. I hadn't thought about that cone shapped sort of inner bowl that takes up about the middle fifth of the bowl.

I had been having bad water ingestion problems for the last couple of years and was taking a lot of water out of my filters, and doing it frequently. It was so bad that my engine died from breathing water several times - and with a carbed engine its a pain in the butt getting them to restart because you have to run all of that water out of the all 3 float bowls. Anyway I was taking out as much as a quart a day, every trip. When I removed the bowls to replace filters this spring you would have fainted if you'd seen the trash that was captured in that little inner bowl. The crap was sort of brown/red and had about the consistancy of tooth paste .... with lumps.

And yep, the new engine is really nice. Its pleasant to be able to go off shore again and not be concerned about making it back, quieter and less fuel use too. I am pleased, very pleased.

Thom
Thom is offline  
Old 06-03-2004, 05:09 PM
  #12    
Senior MemberCaptains Club Member
 
Join Date: Jun 2001
Location: Boynton Beach Fl (Pursuit
Posts: 5,541
Default RE: Fuel/Water Separator-How's it work?

Thom, great! Glad to hear the new power is working out! Didn't you redo some glass work also? If so how about a pic!
KevinM is offline  
Old 06-03-2004, 07:46 PM
  #13    
Senior MemberCaptains Club MemberPLEDGER
 
Join Date: Oct 2002
Location: mass/Point Judith, RI dockage
Posts: 8,511
Default RE: Fuel/Water Separator-How's it work?

Hey thom, hows that 260 working for you?
gerg is offline  
Old 06-03-2004, 07:48 PM
  #14    
Senior MemberCaptains Club Member
 
Join Date: Apr 2004
Location: Portsmouth RI
Posts: 4,139
Default RE: Fuel/Water Separator-How's it work?

You describe it similar to an oil filter, that means it is one of the cheap spin-on ones. Just copy the numbers off it and replace. Should change them out twice a year.
Sleeper is offline  
Old 06-03-2004, 08:57 PM
  #15    
Senior MemberCaptains Club Member
 
Join Date: Nov 2002
Location:
Posts: 111
Default RE: Fuel/Water Separator-How's it work?

What is that reddish brown crap anyway and how does it get to the exit side of the filter? I have noticed it when I removed and replaced my filter. I have to scrap it out of the inner chamber.

Some times there is a minute amount of water with it which clearly indicates the Racor will pass water. I would imagine that water particles might find there way through the filter if they remain suspended and do not fall to the bottom of the bowl quickly. There is another downstream filter installed on the engine so I hope that it is picking up whatever the Racor does not catch.

Thom, I have not forgotten you and will be sending you an e-mail in due course. If you remember, I asked for your mailing address.
marinerman is offline  
Old 06-03-2004, 11:56 PM
  #16    
Junior Member
 
Join Date: May 2004
Location: Bradenton, FL
Posts: 28
Default RE: Fuel/Water Separator-How's it work?

Gents:

Thanks for all the great explanations and advice. I pulled the separator today, dumped it into a jar, and not a drop of water was present. Also pulled the fuel filter in the carb and clean as a whistle. Took 'er out and gave her a good run for about 40 minutes at cruise, and the stall wouldn't happen. Getting frustrated now....

Any other suggestions? I still suspect fuel or ignition related. I checked all the connections (wires) and they're tight. Electric fuel pump? Temp sensor? Knock sensor? Timing module????????

Any thoughts?

Thanks.
__________________
Sincerely,
Michael...
Bradenton, Florida
Knot2shy is offline  
Old 06-04-2004, 08:03 AM
  #17    
Senior MemberCaptains Club Member
 
Join Date: Jan 2002
Location: Sullivans Island SC
Posts: 256
Default RE: Fuel/Water Separator-How's it work?

I had some fuel issues with my repower. I had multiple problems so they may or may not apply to your situation. It first started with the engines bogging down around 1800 RPM. Changed out the filters. Plenty of crap and water in the filters and lines. Probably due to not capping the lines and tanks during the installation. Also had a bad main tank. Cleared the lines, checked the vent, changed filters, worked fine for awhile. Started happening again on the stbd engine. Noticed that the spin on filter would only be a quarter full after every occurrance. Suspected the stbd tank. Ran dedicated lines to each engine and then switched lines from port to stbd. The port engine continued to run fine, stbd engine got better but still bogged at 2400 RPM or 10GPH. Put the stbd engine on a six gallon portable with a primer bulb. When the engine started to bog, had a friend pump the bulb. Ran great as long as he pumped it. Replaced the electric fuel pump. So far so good.

The whole process was pretty frustrating since the symptons were intermittent and the performance improved initially after each step. Seemed like I would have been more clued in since I went through the same symptons with my Tahoe and it's electric fuel pump.

My set up is twin Mercruiser 8.1HO Horizons EFI. 3 Tanks, Common fuel manifold supply to each engine and generator. Each engine has an inline filter to the electric fuel pump and then to the fuel water seperator. The fuel water seperator is a common Mercury item and available at most dealers or boat stores. The inlines are special order and are $50+ each. Fuel pump was $218 and a stock item at a Mercury Dealer.

Symptons were bogging down after load. Sometimes it would happen and then resume normal ops. Sometimes a restart would fix it. I could hear the pumps turn on when I turned the engines on so I initially ruled them out. Changing the pump was the last resort before sending it to the shop. My theory on this whole episode was the pump performance was degraded by all the crap in the main tank and fuel lines. Not sure why Mercruiser designed the engine with the fuel water seperator/ filter after the pump.

This may or may not be your problem. Looking back on this and other websites seemed to indicate bogging down or stalling at increased RPM indicative of fuel restriction. Most people reccomend working from the tank to the carb. Sputtering or misfires tend to indicate an ignition problem once fuel was ruled out.
__________________

Boca Jima - Jim Smith Tournament 40
Tin Man is offline  
Old 06-04-2004, 09:07 AM
  #18    
Member
 
Join Date: Jan 2004
Location:
Posts: 32
Default RE: Fuel/Water Separator-How's it work?

Also check you anti-siphoning valve on your fuel tank. It should be connected to the pick up pipe. I had a similar scenario a few years back. Chased it for two years and finally solved it with a $2 part.

Ghostrider
Niceville FL 255CC Seapro
presson is offline  
 
 
Closed Thread

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Fuel water separator Scoutin 4 Goodies The Boating Forum 0 05-28-2008 06:09 PM
new fuel water separator phillipgo The Boating Forum 10 05-12-2008 12:15 PM
fuel water separator catastrophe The Boating Forum 10 02-02-2007 02:15 PM
Any water in fuel separator? Tedj101 The Boating Forum 18 05-15-2006 08:56 PM
Fuel/Water Separator Purple The Boating Forum 3 05-05-2006 07:43 PM

 



©2009 TheHullTruth.com

Powered by vBulletin® Version 3.7.6
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.2.0