Replacing 1977 55hp carbs with 1976 55hp carbs w/ adj idle screws

[octofoil]

After all the struggles with my 1977 55hp Johnson, all my troubleshooting still points back to carb damage from whomever tried to rebuild it before I owned it. The secondary issue could very well be deteriorated hoses. I cannot find replacement carbs for this with the fixed idle orifice, so I bought a pair of 1976 carbs that have the adjustable idle orifice.

Anyone have any precautionary advice with this retrofit?

In addition, I plan to replace the entire fuel line from the tank (including the tank and fuel pump), all the way to the carbs. I would also like to add a fuel filter between the pump and the carbs. I can't imagine that adding a fuel filter would cause an issue, but I don't have a lot of experience with outboards so am wondering if anyone has had any experience with that too.

 

[F_R]

Make sure the filter you choose will supply enough flow for the engine. Fuel starvation can burn up pistons. Lawn mower filters won't get it.

I suppose some people could screw up anything, but it is highly unusual for those carburetors to be beyond repair.

 

[octofoil]

Thanks for the tip on the paying attention to the flow capacity on the filter. Point well taken.

The problem with the carbs is the brass tube on the idle circuit. One was pushed in too far, and the other was bent. I can try to disassemble once I have the other carbs just in case something goes wrong. I could probably even find replacement tubing that I could fab(can't find any replacement parts for those items), but it appears to be a light press fit in which case I can see having issues at disassembly or reassembly. It seems like a nice simple design so it would be nice to be able to salvage.