1994 merc 4.3L carb issues (190Hp)

[Bigrthanur]

I have a small but bothersum carb issue with my Thompson. It has started everytime for me but it has an extended crank time. 25 to sometimes 40 seconds before it starts? When I am cruising and give it WOT it hesitates for a second or so then takes off like it should.

Also I noticed that if the engine is not running and put the throttle to WOT the carb plenums are not all the way open (4 bbl carb). Seems to me that they should be 100% open?

The engine has 182hrs and do not think anything has been done to the engine other than a tune up oil change ect.

Any help is appreciated.

Thanks

 

[searay3]

Re: 1994 merc 4.3L carb issues (190Hp)

Do you set the throttle as you would to start a carbed engine or leave the throttle at idle like fuel injection? There is a huge difference at startup. If you are using the correct startup procedure the carb may need rebuilt. Hesistation is a symptom of a worn accelerator pump. There is no point in working over the carb if the tuneup is a couple of seasons old. Make sure that is done before diggin into the carb. Check the adjustment of the throttle cable, the butterflies need to open completely.

 

[Bondo]

Re: 1994 merc 4.3L carb issues (190Hp)

I have a small but bothersum carb issue with my Thompson. It has started everytime for me but it has an extended crank time. 25 to sometimes 40 seconds before it starts? When I am cruising and give it WOT it hesitates for a second or so then takes off like it should.

Also I noticed that if the engine is not running and put the throttle to WOT the carb plenums are not all the way open (4 bbl carb). Seems to me that they should be 100% open?

The engine has 182hrs and do not think anything has been done to the engine other than a tune up oil change ect.

Any help is appreciated.

Thanks

Ayuh,.... Is this the Merc/ Weber 4 bbl. carb,..??

 

[Bigrthanur]

Re: 1994 merc 4.3L carb issues (190Hp)

Not sure of the carb manufacturer but I can check when I get it back out next weekend.

I do not start the boat using a carb set up I just try to pump it once or twice then crank it, till she starts. I was thinking the accelerator pump as well.

Anyone have a link on how to properly adjust the throttle cable?

 

[Bigrthanur]

Re: 1994 merc 4.3L carb issues (190Hp)

Ayuh,.... Is this the Merc/ Weber 4 bbl. carb,..??

Yes it is a weber carb.

 

[Bondo]

Re: 1994 merc 4.3L carb issues (190Hp)

I have a small but bothersum carb issue with my Thompson. It has started everytime for me but it has an extended crank time. 25 to sometimes 40 seconds before it starts? When I am cruising and give it WOT it hesitates for a second or so then takes off like it should.

Also I noticed that if the engine is not running and put the throttle to WOT the carb plenums are not all the way open (4 bbl carb). Seems to me that they should be 100% open?

The engine has 182hrs and do not think anything has been done to the engine other than a tune up oil change ect.

Any help is appreciated.

Thanks

Ayuh,.... That carb is known to leak down, when not runnin',...
Some of Us have wired in a momentary switch in the fuel pump circuit to by-pass the o/p safety switch to prime the carb, after it's been sittin'...

The Bog when acceleratin' could be crud in the jets, or the acc. pump needin' adjustin'...

And,... The aft carb ports have a vacuum actuated door,...
So, with the motor Not runnin', the secondaries won't open...

 

[achris]

Re: 1994 merc 4.3L carb issues (190Hp)

Yep, those buggers dribble... PITA!!! Don't usually need to worry about anything in the ignition system except the spark plugs... New ones every 200 hours, and use NGK NOT Champions... My previous engine was a '94 4.3LX... Just like yours. I checked the timing from the factory (8? BTDC) and then again every few years... It never moved. That engine is in a friends' boat now, and the timing is still 8? BTDC... I also have another friend with the '95 4.3LX... Same story, never moves from 8? BTDC.... But yeah, those carbs are a nuisance. I tried EVERYTHING to fix the problem... I analyzed it to death.. Found out it was the internal passages, they appear to be too small, and the fuel flows up through them even when the engine's not running, called 'capillary action'.... Talked to a lot of 'carbie experts'... yeah, they told me it can't happen... Yeah right!!! When I demonstrate, they run away.... Bloody cowards!

Anyway, I was thinking of replacing it (the Weber) with an Edelbrock 1409, but a nice deal came along and I swapped it for a brand new 4.3MPI.... Worst day of my life!!! Damn plastic timing covers kept breaking (and Merc refused to cover it on warranty)... I kept getting a ****ty oily mess in my nice clean bilge... Thanks Merc, thanks for nothing!!! I want my old V6 back!!!...

Sorry, got diverted... Yeah, your problem.... Welcome to a very large club....

Chris..........

EDIT: Hey man, check it out!!!! 9,999 posts.... Next post and I'm a 'Supremo Marinero'... Yea har!!!

 

[Bigrthanur]

Re: 1994 merc 4.3L carb issues (190Hp)

Thanks