1991 Mercruiser 3.0L Carb Running Rich

[Roadblock007]

My boat has been running very rich so I adjusted the carb as per the manual and it was still idling at 1600 rpm. You could smell gas and the exhaust was black. I pulled the carb and the intake was absolutely soaked with gas. I am going to rebuild it but my local marine shop says the Mercarb has no rebuild kit, just parts sold separately. Is that true?

 

[Scott06]

They are available right here t iboats, you'll find plenty of carb kits available. Pretty sure the merc part number is 3302-804844002 but best to get the carb number off the carb by the fuel inlet

I think this is the Sierra kit from iboats you need https://www.iboats.com/shop/sierra-carburetor-kit-18-7098-1.html

 

[Roadblock007]

Someone painted the carb black and when I cleaned it off I can't read the numbers.

 

[Scott06]

That's the way they come from the factory painted black.they are stamped into the housing

 

[Roadblock007]

Either way, the numbers are so faint that they are almost gone. I can't read them at all.

 

[Roadblock007]

Doing some research I have noticed that for my engine there were only 2 carbs, 1389-9562 (36mm) and 1389-815396(43mm). How do I tell the difference without knowing that number on the housing?

 

[Roadblock007]

Last question. I finished the rebuild with new float and have made all the adjustments by the book. I watched the teardown and rebuild videos on you tube and now I notice that the throttle lever does not contact idle cam. It has no hook on it to catch the cam as it rotates. Is this normal?

 

[achris]

Doing some research I have noticed that for my engine there were only 2 carbs, 1389-9562 (36mm) and 1389-815396(43mm). How do I tell the difference without knowing that number on the housing?

By posting your engine serial number.

Last question. I finished the rebuild with new float and have made all the adjustments by the book. I watched the teardown and rebuild videos on you tube and now I notice that the throttle lever does not contact idle cam. It has no hook on it to catch the cam as it rotates. Is this normal?

This is what it should look like...

 

[Roadblock007]

By posting your engine serial number.



This is what it should look like...

That is what it looks like. However the throttle lever on my carb has no tang to engage the hook on the idle cam. Upon looking at more google pictures of the mercarbs I can see that some do and some don't. Just didn't seem right.

My engine serial number is OD610854.

 

[Roadblock007]

Reinstalled the carb and after a few seconds of cranking it fired right up. No smoke but ran a bit rough. Warmed it up and dialed it in a bit better. I brought it to 900 rpm's at idle and smoothed out the mixture and it ran great. I wanted to leave the idle there on the muffs and I will do final adjustments on the water. I figure the idle will drop once the boat is in the water.

Thanks for all the help!

 

[Scott06]

Yes idle will drop when in gear and on the water, but probably not the 250-300 you need it to drop. Just set it when in gear.

 

[achris]

Idle speed needs to be set with the boat in the water, in forward gear, and not tied up to a pier or jetty. ie, take someone who will steer while you set the mixtures and speed (and use a digital tacho for setting the speed, not the dash tacho)... Idle speed spec is 650-700rpm...

Chris........