Mercruiser 4.3 LX 1994 hard starts after the boat engine runs for some time

[jman89]

I'm trying to fix my Mercruiser 4.3 LX 1994 engine from hard starts after the boat engine runs for some time. My stingray 1994 zp engine can sit for weeks outside of the water and will start up fine and run great. When I launch the boat and start the engine, the engine starts right up and everything is fine. Although after driving for more than 15 minutes and stopping the boat, the next start up will be a little harder and the next start up after that will be even worse and take over 10 seconds to crank over while giving it a lot of throttle/full throttle in neutral to start up; Basically I'm saying the start up time gets worse. I will have to wait a half hour for the boat to start up without problems but then after, the problem repeats.

I've done the following:
Replaced all spark plugs
Cleaned the carburetor
Replaced the belts

A few things I've looked into but haven't checked are:
checking to see if water is in the fuel pump
checking the pressure on the cylinder valves

Does anyone have any information on a part in the engine to check or things I could test? Any information solving this issue would be great. Thank you.

 

[Rick Stephens]

Wonder if the carb is draining fuel in and flooding the motor?

 

[Bondo]

Ayuh,...... Welcome Aboard,...... Do you advance the throttle when starting,..??

 

[achris]

Wonder if the carb is draining fuel in and flooding the motor?

Yes it is. It's the infamous Weber 9600 'Dribbler' carb.

2 ways to fix it... Replace the carb with an edlebrock 1409, or replace the engine with an MPI...

Chris....

 

[jman89]

Ayuh,...... Welcome Aboard,...... Do you advance the throttle when starting,..??

Yes I do. On the first starts, I don't need to use the throttle in neutral but when it starts having hard starts, I need to give it more throttle in neutral.

 

[jman89]

Yes it is. It's the infamous Weber 9600 'Dribbler' carb.

2 ways to fix it... Replace the carb with an edlebrock 1409, or replace the engine with an MPI...

Chris....

Most likely I would replace the carb since it seems like an easier fix but I could be wrong as I am a beginning in learning engines especially for boats.

I was doing some research and a lot of other sources point to the vapor lock leak. After the motor has been running and shuts off, it's really hot and there's too much heat to ignite a start to the engine which is what I'm thinking what the problem is. Is the vapor lock the same as the carburetor or some part of it?

So, would me trying to start the engine up in 10 seconds or more result in the carb flooding the engine because of me trying to start it up/crank over for 10 seconds?

 

[achris]

The Weber dribble is well documented and known. Personally,I have pulled the top of a carb and watched it dribble, on 2 difference carbs...

It's not a vapour lock problem....

Chris...

 

[Bondo]

Is the vapor lock the same as the carburetor or some part of it?

Nope,..... Vapor lock is a condition,........ Not a part of anything,......

'n I agree with Chris,..... I doubt vapor lock as anything to do with yer problem,.......

I've got the same carb,..... Wot hot starts are common to clear the flooded motor, from the dribble,.....

 

[Rick Stephens]

Boats generally have unlimited cooling. Vapor locks are when the fuel line is so hot that the fuel boils inside and turns to vapor. That generally doesn't occur with most boats - they shouldn't ever get hot in the doghouse and the motors, especially with sea water cooled which never get much above 150ƒ. That is on purpose, to run a motor hotter than that takes pressurizing the cooling system or the cooling water start creating bubbles inside the motor passages and hot spots are the result. So unless you have a closed cooling system, your motor is not getting near hot enough to cause a vapor lock.

 

[jman89]

Yes it is. It's the infamous Weber 9600 'Dribbler' carb.

2 ways to fix it... Replace the carb with an edlebrock 1409, or replace the engine with an MPI...

Chris....

Hey achris, I will start to plan on inspecting the carburetor and possibly replacing it. Is this the correct type of Edelbrock 1409 carburetor you were talking about replacing it with? I attached two screenshots below in this post of photos of the carburetor from Amazon.

 

[Bondo]

Ayuh,..... That's the carb,.....