Mercruiser 4.3 carb issues

[Kschoen123]

Hey Guys,

I've been reading the forums for a long time but this is my first post. Engine serial number is OC866571. I am working on rebuilding my carb but ran stuck here. I believe it's a mercarb, its a 2 barrel. I got a number off the side, 33049565 9Y02. The choke is stuck open, i can close it a bit by hand but it is binding inside the carb I can see the rub marks on either side. I took off the linkage and the spring to make sure and a also loosened the screw holding the choke plate and tried to center it better but its just too tight in there. Also, the bracket for the flame arrestor is broken? Has anyone ever had this before?

 

[Yegboats]

Def. a mercarb 9565a 1 807764a 1
Merc 4.3L 1990

 

[Bondo]

The choke is stuck open, i can close it a bit by hand but it is binding inside the carb I can see the rub marks on either side. I took off the linkage and the spring to make sure and a also loosened the screw holding the choke plate and tried to center it better but its just too tight in there. Also, the bracket for the flame arrestor is broken? Has anyone ever had this before?

Ayuh,.... Welcome Aboard,..... It appears that it was Smashed, Badly,....

The carb's top castin' is knocked outa round, 'n badly bent up,....

A replacement is the only way I know of, to fix it,.....

 

[Kschoen123]

Ayuh,.... Welcome Aboard,..... It appears that it was Smashed, Badly,....

The carb's top castin' is knocked outa round, 'n badly bent up,....

A replacement is the only way I know of, to fix it,.....

Thanks guys,
Can i buy just the air horn for the carb or would a complete replacement be in order?

 

[Rick Stephens]

Doesn't appear that the air horn is sold individually.

 

[Kschoen123]

hmmm $$$.... that sucks

 

[Rick Stephens]

Choice seems to be buy a new mercarb, buy a used mercarb, or get a different brand or model carb. I'll bet you can find a used one at a dealer or off Craigslist or eBay and use it for parts.

 

[Kschoen123]

Is it out of the question to very lightly file off a bit of the choke plate where it's binding or is that a bad idea?

 

[Rick Stephens]

Is it out of the question to very lightly file off a bit of the choke plate where it's binding or is that a bad idea?

if it runs.... why not? flows will change a little being bent, no one can tell you it will actually work right without they hold it in their hands and do the filing themselves. you'll have to decide.

 

[Kschoen123]

if it runs.... why not? flows will change a little being bent, no one can tell you it will actually work right without they hold it in their hands and do the filing themselves. you'll have to decide.

Ok i think i'll try that. On the water muffs it runs just fine with the choke stuck open. Give it a couple pumps and it fires right up and idles just fine cold. I wonder if my idle circuit is set too rich. I think i'll rebuild it, get everything set right and file down the plate to get it working and see where i'm at. The boat is new to me, just bought it last fall. I've only had it out once and at the time i didn't know the correct starting procedure (my last boat had an inline 6 150hp) so i just cranked it over till it started. Worst case scenario it doesn't work and i need a new one. Thanks!!

 

[Bondo]

Worst case scenario it doesn't work and i need a new one.

Ayuh,..... If it comes to that, a 4bbl. carb 'n manifold will get ya 'bouta 20hp increase,....

 

[Kschoen123]

Ayuh,..... If it comes to that, a 4bbl. carb 'n manifold will get ya 'bouta 20hp increase,....

Yeah that's what i was planning to do if i need to. Question though, i'm not worried about top speed near as much as holeshot, I slalom ski with suicide boots and i'm around 205lbs so i don't come out of the water easy. Does a 4bbl give more bottom end torque as well or is it just peak hp? I haven't skied behind this boat yet... Hopefully it works well enough with the 2bbl. It's a glascon 170 Ultra, 17' and its registered at 1375lbs (not sure how accurate that is though) Alpha one drive with a high 5 19p. I'm itching to try it out but need to finish the tune up first....

 

[Speak]

Hey K - I had the same problem - I think it happens if the motor is lifted out for some reason or another and the lifting chain is not routed properly presiding on the carb body. I did exactly what you did - worked great

 

[Bondo]

Yeah that's what i was planning to do if i need to. Question though, i'm not worried about top speed near as much as holeshot, I slalom ski with suicide boots and i'm around 205lbs so i don't come out of the water easy. Does a 4bbl give more bottom end torque as well or is it just peak hp? I haven't skied behind this boat yet... Hopefully it works well enough with the 2bbl. It's a glascon 170 Ultra, 17' and its registered at 1375lbs (not sure how accurate that is though) Alpha one drive with a high 5 19p. I'm itching to try it out but need to finish the tune up first....

Ayuh,.... I believe the horsepower increase is throughout the rpm band, but if a boat won't pull yer butt outa the water, a drop in prop pitch oughta fix that,....

 

[Kschoen123]

Hey K - I had the same problem - I think it happens if the motor is lifted out for some reason or another and the lifting chain is not routed properly presiding on the carb body. I did exactly what you did - worked great

That makes a lot of sense. My engine bay is really tight, i can't get the flame arrestor off without first removing the carb because there's not much clearance. I could definitely see someone running the chains really tight just for clearance and then of course hit the carb. Good to hear that it worked for you! I'll try it out this aft hopefully.