Greetings,

I was on the lake yesterday in my '93, 18ft Thompson 4.3L Mercruiser,
with carburetor and electric fuel pump.

The engine literally locked up when coming to a 'slow down' with the
boat. I tried to restart it and it acted like a low battery. The first
thing I thought of is: "ok we're overheated" but the temperature was way
under 150.

The engine had a pretty big jerk from the starter trying so hard. so I
knew it wasn't a low battery or bad starter. Sometimes I would get it
started and all of a sudden a lock up.
I had to be towed back to the boat ramp. This engine did not overheat. I
felt the manifolds and they wasn't barely even warm.

When I got home - I hooked up the ear muffs and it started right up. Ran
normal. It had me scratching my head.

I checked the oil and noticed it was about 2 quarts over the full mark.
It was not milky. So no water getting in the oil. I drained the oil and
it smelled like gas. I'm guessing gas is getting into the oil from the
Carb. So the engine lock up was from the crankcase being totally full of
oil (and gas in this case.)

Now my questions a Do I just need a Carb rebuild kit, or new Carb? Is
there anything else that can cause this? Has anyone ever had this
problem?
Thanks for any comments/opinions.
Sonny

Sonny H wrote:
Greetings,

I was on the lake yesterday in my '93, 18ft Thompson 4.3L Mercruiser,
with carburetor and electric fuel pump.

Ok definitely "electric" fuel pump not mounted low down on the block???


The engine literally locked up when coming to a 'slow down' with the
boat. I tried to restart it and it acted like a low battery. The first
thing I thought of is: "ok we're overheated" but the temperature was way
under 150.

The engine had a pretty big jerk from the starter trying so hard. so I
knew it wasn't a low battery or bad starter. Sometimes I would get it
started and all of a sudden a lock up.
I had to be towed back to the boat ramp. This engine did not overheat. I
felt the manifolds and they wasn't barely even warm.

When I got home - I hooked up the ear muffs and it started right up. Ran
normal. It had me scratching my head.

I checked the oil and noticed it was about 2 quarts over the full mark.
It was not milky. So no water getting in the oil. I drained the oil and
it smelled like gas. I'm guessing gas is getting into the oil from the
Carb. So the engine lock up was from the crankcase being totally full of
oil (and gas in this case.)

Now my questions a Do I just need a Carb rebuild kit, or new Carb?

Probably just a kit or it might even be as easy as just unstick the
float needle?? There's always the chance a lead plug in the carb's
drillings has come adrift & has allowed a leak.

Is
there anything else that can cause this?

With a marine carb any venting or overflow say from a stuck float
needle is directed down the carb throat. i.e. a serious over flow/leak
of fuel should stop the engine (being too rich not seized:-)) but if you
have a lesser leak it's possible raw fuel can get into the cyl (usually
after/during stops), it gets past the rings & is where you found it.

Change the oil & filter, start it & make sure it's running, idling etc
OK if there is excess fuel getting in from any source it will show in
the running. Stop it & make sure there's no excessive raw petrol smell
down the throat. If all is OK then it's probably just the float
needle/seat, renew or;

If you have an electric pump with adjustable pressure??? make sure it's
not turned up lots too high (equally don't just turn it right down,
creates another problem "lean" at power), so at high vibration & flow
the excess pressure is getting past a slightly worn needle & seat; not a
proper fix & a carb kit with new needle & seat can't be dear.

K
Has anyone ever had this
problem?
Thanks for any comments/opinions.
Sonny

WaIIy wrote:
On Sat, 04 Dec 2004 09:42:52 +1100, "K. Smith" wrote:


With a marine carb any venting or overflow say from a stuck float
needle is directed down the carb throat. i.e. a serious over flow/leak
of fuel should stop the engine (being too rich not seized:-)) but if you


The carb on my 5.7 was lunched (bad float or seal) and there a gas
puddle on top of my engine

Thanks Wally, marine carb I assume??? not supposed to happen save some
overflow can get past the accelerator pump link.


K

WaIIy wrote:
On Sat, 04 Dec 2004 10:28:26 +1100, "K. Smith" wrote:


WaIIy wrote:

On Sat, 04 Dec 2004 09:42:52 +1100, "K. Smith" wrote:



With a marine carb any venting or overflow say from a stuck float
needle is directed down the carb throat. i.e. a serious over flow/leak
of fuel should stop the engine (being too rich not seized:-)) but if you


The carb on my 5.7 was lunched (bad float or seal) and there a gas
puddle on top of my engine

Thanks Wally, marine carb I assume??? not supposed to happen save some
overflow can get past the accelerator pump link.


K


Yup, marine carb on a 1989 5.7 Mercruiser. I was surprised to see the
gas puddled in my manifold.

I bet you were!!!:-) Take care.


K

Leaks past the throttle shafts.

"WaIIy" wrote in message
...
On Sat, 04 Dec 2004 10:28:26 +1100, "K. Smith" wrote:

WaIIy wrote:
On Sat, 04 Dec 2004 09:42:52 +1100, "K. Smith" wrote:


With a marine carb any venting or overflow say from a stuck float
needle is directed down the carb throat. i.e. a serious over flow/leak
of fuel should stop the engine (being too rich not seized:-)) but if you


The carb on my 5.7 was lunched (bad float or seal) and there a gas
puddle on top of my engine

Thanks Wally, marine carb I assume??? not supposed to happen save some
overflow can get past the accelerator pump link.


K

Yup, marine carb on a 1989 5.7 Mercruiser. I was surprised to see the
gas puddled in my manifold.

JamesgangNC wrote:
Leaks past the throttle shafts.

Yes!!!!! thanks James, I knew it was supposed to end up in the throat,
but as you say if the throttles are shut, then ....

Thanks.

K


"WaIIy" wrote in message
...

On Sat, 04 Dec 2004 10:28:26 +1100, "K. Smith" wrote:


WaIIy wrote:

On Sat, 04 Dec 2004 09:42:52 +1100, "K. Smith" wrote:



With a marine carb any venting or overflow say from a stuck float
needle is directed down the carb throat. i.e. a serious over flow/leak
of fuel should stop the engine (being too rich not seized:-)) but if you


The carb on my 5.7 was lunched (bad float or seal) and there a gas
puddle on top of my engine

Thanks Wally, marine carb I assume??? not supposed to happen save some
overflow can get past the accelerator pump link.


K

Yup, marine carb on a 1989 5.7 Mercruiser. I was surprised to see the
gas puddled in my manifold.

Does sound like a stuck carb float. An electric fuel pump with a regular
carb is not a common combination for a 4.3 merc. Are you sure about the
electric fuel pump? 93 is old enough to still have a regular carb. I'd
certainly try a rebuild kit and I'd probably only go as far as the float
bowl when I did it. 4 barrel or 2 barrel?

"Sonny H" wrote in message
...
Greetings,

I was on the lake yesterday in my '93, 18ft Thompson 4.3L Mercruiser,
with carburetor and electric fuel pump.

The engine literally locked up when coming to a 'slow down' with the
boat. I tried to restart it and it acted like a low battery. The first
thing I thought of is: "ok we're overheated" but the temperature was way
under 150.

The engine had a pretty big jerk from the starter trying so hard. so I
knew it wasn't a low battery or bad starter. Sometimes I would get it
started and all of a sudden a lock up.
I had to be towed back to the boat ramp. This engine did not overheat. I
felt the manifolds and they wasn't barely even warm.

When I got home - I hooked up the ear muffs and it started right up. Ran
normal. It had me scratching my head.

I checked the oil and noticed it was about 2 quarts over the full mark.
It was not milky. So no water getting in the oil. I drained the oil and
it smelled like gas. I'm guessing gas is getting into the oil from the
Carb. So the engine lock up was from the crankcase being totally full of
oil (and gas in this case.)

Now my questions a Do I just need a Carb rebuild kit, or new Carb? Is
there anything else that can cause this? Has anyone ever had this
problem?
Thanks for any comments/opinions.
Sonny

"WaIIy" wrote in message
...
On Sat, 04 Dec 2004 09:42:52 +1100, "K. Smith" wrote:

With a marine carb any venting or overflow say from a stuck float
needle is directed down the carb throat. i.e. a serious over flow/leak
of fuel should stop the engine (being too rich not seized:-)) but if you

The carb on my 5.7 was lunched (bad float or seal) and there a gas
puddle on top of my engine

Should not happen if a marine carb! The vent tubes are J shaped to dump the
extra fuel from a stuck float into the throttle bore. Probably what
happened on the original post. The electric fuel pump kept pumping way
longer than it should have. Does it have a pump while engine running
circuit? Should have. Also the throttle shafts on a marine carb have flats
and grooves there they ride in the carb housing to keep fuel inside the
carb.
Bill

Check and make sure you still don't have the mechanical fuel pump attached
to the motor. It the electric fuel pump is down stream of the mechanical and
the mechanical pump has a blown diaphragm you could be pumping fuel directly
into the crankcase.

I had the same problem with my boat.
the float is sticking in the carb, which allows the gas flow to increase
drematicaly. YOU DON'T HAVE TO REBUILD THE CARB!!! Just open it up
carefully. clean out the the area where your float is located. try not to
damage the gasket.
Make sure the float will move up and down very easly.
However, if it does not, then you will need to install a carburater kit.