Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 08-01-2020, 14:30   #1
Registered User

Join Date: May 2014
Location: So Cal
Boat: Beneteau 38 Nordlund 72, Marquess 55, Jenneau 49
Posts: 491
Small outboard crank case flooding with fuel

I have a 2009 Mercury 6hp 4 Stroke. I have gasoline entering my crank case and I don't know why.



I have serviced the carburetor and needle valve and both look good.



I have checked the needle valve with vacuum tester and holds vacuum.



The compression was good.



It's blowing grey smoke even after an oil change. I've done 4 oil changes now to remove all the gas from the crank.



Why is the crank filling with fuel? I am stumped. Any and all advice on how to remedy this problem would be greatly appreciated. Thank you!
__________________

Valmika is offline   Reply With Quote
Old 08-01-2020, 14:44   #2
Registered User

Join Date: Jan 2008
Location: SF Bay Area (Boat in La Paz)
Boat: Valiant V40
Posts: 755
Re: Small outboard crank case flooding with fuel

Don't know this OB, but most have a diaphragm fuel pump operated by crankcase pressure/vacuum, so could be a failed diaphragm.
__________________

jamhass is offline   Reply With Quote
Old 08-01-2020, 14:46   #3
Registered User

Join Date: May 2013
Location: Tilloo Cay, Abaco, Bahamas
Boat: Catalina 42
Posts: 185
Re: Small outboard crank case flooding with fuel

My guess is it has a diaphragm fuel pump mounted on the crankcase, and that diaphragm is busted and it pumps fuel into the crankcase as well as the carb...
Jam beat me to it.
Empty Pockets is offline   Reply With Quote
Old 09-01-2020, 08:26   #4
Registered User

Join Date: May 2014
Location: So Cal
Boat: Beneteau 38 Nordlund 72, Marquess 55, Jenneau 49
Posts: 491
Re: Small outboard crank case flooding with fuel

We did check the pump and it looked as if diaphragm was intact. We will try to figure a way to pressure test it. I am wondering if the needle valve is faulty even though we tested with a vacuum pump (maybe we were helping it seal) Question: if the needle valve is bad and overflows the bowl wouldnt the just drain out, not get sucked into the carb?
Valmika is offline   Reply With Quote
Old 09-01-2020, 09:21   #5
Registered User

Join Date: Aug 2014
Location: Palm Beach Gardens, FL
Posts: 42
Re: Small outboard crank case flooding with fuel

On most 4 stroke outboards, if you lay them down with the wrong side up, the gas will drain through the carb into the crankcase and/or the compression chamber.
Var Korall is offline   Reply With Quote
Old 09-01-2020, 09:53   #6
Registered User

Join Date: Oct 2016
Posts: 8
Re: Small outboard crank case flooding with fuel

Valmika,
It happened to me and it WAS the fuel pump.
Best regards,
Steve Baum
srbaum is offline   Reply With Quote
Old 09-01-2020, 13:01   #7
Registered User

Join Date: May 2014
Location: So Cal
Boat: Beneteau 38 Nordlund 72, Marquess 55, Jenneau 49
Posts: 491
Re: Small outboard crank case flooding with fuel

Quote:
Originally Posted by Var Korall View Post
On most 4 stroke outboards, if you lay them down with the wrong side up, the gas will drain through the carb into the crankcase and/or the compression chamber.

This happens while the engine is running in a barrel for less than 10 minutes it puts about 2 oz of fuel into the oil
Valmika is offline   Reply With Quote
Old 09-01-2020, 13:45   #8
Registered User

Join Date: May 2014
Location: So Cal
Boat: Beneteau 38 Nordlund 72, Marquess 55, Jenneau 49
Posts: 491
Re: Small outboard crank case flooding with fuel

Quote:
Originally Posted by srbaum View Post
Valmika,
It happened to me and it WAS the fuel pump.
Best regards,
Steve Baum



Thanks Steve. We will go back and look at the FP again.
Valmika is offline   Reply With Quote
Old 09-01-2020, 13:57   #9
Registered User
 
liquidice's Avatar

Join Date: May 2017
Location: Chicago
Boat: Catalina Capri 25
Posts: 232
Re: Small outboard crank case flooding with fuel

Quote:
Originally Posted by Valmika View Post
I have a 2009 Mercury 6hp 4 Stroke. I have gasoline entering my crank case and I don't know why.



I have serviced the carburetor and needle valve and both look good.



I have checked the needle valve with vacuum tester and holds vacuum.



The compression was good.



It's blowing grey smoke even after an oil change. I've done 4 oil changes now to remove all the gas from the crank.



Why is the crank filling with fuel? I am stumped. Any and all advice on how to remedy this problem would be greatly appreciated. Thank you!


Sounds like the symptoms I had with a Honda 7.5 hp that ended up being a cracked head. It started and ran, but when I revved it up, oil escaped. Just a (sad) idea.
liquidice is offline   Reply With Quote
Old 10-01-2020, 12:00   #10
Registered User

Join Date: May 2014
Location: So Cal
Boat: Beneteau 38 Nordlund 72, Marquess 55, Jenneau 49
Posts: 491
Re: Small outboard crank case flooding with fuel

Quote:
Originally Posted by liquidice View Post
Sounds like the symptoms I had with a Honda 7.5 hp that ended up being a cracked head. It started and ran, but when I revved it up, oil escaped. Just a (sad) idea.

I am trying to think of how a cracked head could put fuel in the crankcase oil. Can you elaborate? We will be checking compression and fuel pump again today.
Valmika is offline   Reply With Quote
Old 11-01-2020, 02:13   #11
Registered User

Join Date: Sep 2007
Location: Queensland, Australia
Boat: None at present--between vessels. Ex Piver Loadstar 12.5 metres
Posts: 1,265
Re: Small outboard crank case flooding with fuel

Sounds like a perforated fuel pump diaphragm.
Mike Banks is offline   Reply With Quote
Old 18-01-2020, 09:43   #12
Registered User

Join Date: May 2014
Location: So Cal
Boat: Beneteau 38 Nordlund 72, Marquess 55, Jenneau 49
Posts: 491
Re: Small outboard crank case flooding with fuel

Thank You everyone. It looks like it was the fuel pump. It looked intact and I pressure tested it (with my own lungs) and it seemed good but it was not. Thank you all once again.
Valmika is offline   Reply With Quote
Old 18-01-2020, 10:10   #13
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,110
Re: Small outboard crank case flooding with fuel

If you have one of those CARB compliment fuel cans that won’t vent, that swell up in the sun etc that can cause it, they won’t vent so they build pressure which can cause the pump diaphragm to tear or it can overwhelm the needle and float and flood the engine that way, if you have one of those cans get into the the habit of disconnecting the fuel line when your not using the motor or get a non compliant can.
They are sold on Amazon.
__________________

a64pilot is offline   Reply With Quote
Reply

Tags
fuel, outboard

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

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
Gardner 5LW mystery holes in crank case pwillems Engines and Propulsion Systems 0 12-06-2016 06:00
How To Free Coolant Screw-in Lugs In Ford 2701 Lees Dorset Crank Case? Shanaly Engines and Propulsion Systems 2 16-06-2013 17:40
For Sale: Dry Case Waterproof Phone, Camera & MP3 Case - NEW off-the-grid Classifieds Archive 2 11-07-2012 14:58
Flooding, Flooding, Flooding Sea Maid General Sailing Forum 4 03-05-2010 16:33
outboard flooding captden Engines and Propulsion Systems 5 01-06-2008 11:17

Advertise Here


All times are GMT -7. The time now is 11:45.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.