So a couple months ago I purchased a Maxum SCR 2300 from 1991 with a Mercruiser 4.3 175HP Alphe One Gen2.
The engine was not revving for more than 3300.
Checked compression, changed sparkplugs and some other things and now the engine works well, towing WOT ~4400. ( Saw on engine cover that on this one WOT should be 4400-4800 ).
But now a bigger issue came. The boat works very well but after I push it, at around ~4000 RPM, if I go back to lower RPM the carburetor keeps on feeding it gas and when I go to idle it stalles and gas keeps on going into the carburetor.
First I thought it was the float needle that is not working well and I purchased a Carburetor fixing kit, changed everything but still has the same issue. After pushing it more than 4000 RPM the gas keeps on coming and coming and gave me an outrageous fuel consumption of around 60 Liters per hour.
I'm out of ideas, any1 had this issue ?
I want to point out that if you keep the boat at ~3500RPM nothing happens. It idles well afterwards. If you go 4000 and let it on idle it stalls and keeps on pushing gas in the carburetor.
First running at or near WOT should only be done for a few minutes at most. These are converted automotive engines and are not designed for continuous operation at this rpm. I don’t recall what year the 4.3 started using an electric fuel pump but 1991 is close. If the fuel pump is putting out to high of a pressure it can cause your issue. How sure are you of your carburetor rebuild skills? These can be tricky to setup correctly.
The rebuild was made by a mechanic not me .
After rebuild is the same issue, what I forgot to add is that gas is boiling inside the carb for some time after the engine dies on idle.
Is boiling and looks like gas keeps on coming.
Saw some posts that might indicate needing to add an phenolic carburetor spacer.
Was thinking about the pump also.. When I take out the fuel line from the carburetor it comes out with pressure.
I’m surprised that there isn’t a phenolic spacer already as this is a common issue with boats as the engine is in a confined area. The fuel pumps output pressure should be around 6-7 psi.
I cant find it.. Found a diagram and looks like my engine came without the spacer, been added on the later models.
Does any1 have a link for the 2bbl carb spacer ? 🫠 0D606436 is my serial enginer number..
I believe that the leading "0" is a placeholder for future growth.
D606436
This puts it as a Model 175/4.3L (2bbl.) between 1987 -1992. Since the vessel is a 1991, this makes sense.
This is why you need to spend a few dollars and get an official service manual. Call your local Merc dealer and order a service manual based on the serial number.
Mercruiser 4.3 175HP Carburetor issue.
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Linear Mode
