The line most likely once was clear, but is now yellow with age, and not
nearly so transparant to see any fluid flowing in it. However, I have
already decided to replace the fuel pump based on advice from two automotive
mechanics and one Yamaha certified marine engine tech as well as the
postings I have recieve on this and other newsgroups I posted this on. I
believe you're probably correct in that the line is most likely supposed to
be transparant for reasons you stated, so I intend to also replace this bit
of tubing as well. I gotta tell you, though, I do appereciate the responses
I have recieved, and I thank you for taking the time to reply to my little
problem. And, I did learn something about mechanical fuel pumps that 20+
years of shade tree mechanics never taught me - that they can still deliver
fuel even with a ruptured diaphragm, a fact confirmed by all three certified
mechanics confirmed. Thank you once again for your reply.
"Peggie Hall" wrote in message
. ..
Kevin Jed wrote:
I have a Mercruiser 120 fuel problem. There is a small tube going from
the
fuel pump to the throat of the carburetor (like a vacuum tube) and it is
injecting a large volume of fuel into the carburetor throat, bypassing
the
float assembly altogether and flooding the engine. When I remove this
tube
and attempt to plug it, the engine runs properly but there is so much
pressure on this little tube it blows the plug out and starts pouring raw
fuel into the boat! Automotive engines don't have this tube, and I don't
know what it's purpose is. Can anyone offer any help? Thanks!
This is a bit out of my area of professional expertise, but I've had
experience (that included a VERY expensive lesson!) with mechanical fuel
pumps on my own Mercruiser and Chrysler engines...I know just enough about
this to be dangerous.
Inboard marine engines are designed to dump fuel into the oil crankcase if
the diaphragm fails...that's a safety measure, to keep gas--and especially
gas fumes--out of the bilge. That line--which is called a "sight tube" and
SHOULD be clear hose (although it's entirely possible that someone who
knew even less than you do replaced it with black hose) that lets you see
whether anything is going through it. If it's squirting gas, I'd bet real
money that the diaphragm HAS failed. The lifespan of most diaphragms is
only about 5-7 years...if the boat has sat unused for any length of time,
it can be even shorter, 'cuz the diaphragm can dry out and split when the
boat is fired up again. So I THINK you need a new fuel pump. Fortunately,
manual fuel pumps are a lot less expensive than electric fuel pumps.
But, as I said above, I know just about enough about engines to be
dangerous. So before you do anything--especially before you run the boat
again, get the manual for the engine so you'll not only know how to
install a marine fuel pump correctly, but the rest of what you need to
know about the difference between that engine and its automotive
counterpart. And also talk to a certified Mercruiser mechanic...'cuz you
can get all kinds WAG advice here...but HE'LL have the RIGHT advice.
--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://www.seaworthy.com/store/custo...0&cat=6&page=1