First DIY Carb Rebuild...Surprised and Curious

htr2133

Seaman
Joined
Jun 2, 2011
Messages
74
I have a 73 Johnson 6hp Seahorse. This motor was on my dad's first boat, which he purchased when I was going into 6th grade. Boat, Motor, Trailer, Trolling Motor, Battery, Paddles, Life Jackets, and some fishing gear for a total of $600. We used the mess out of that old rig for 20+ years. My dad upgraded 3-4 years ago and I inherited "The little 6" as we call it.

The motor has been giving me fits of some sort or another since I received it. But, I know it is a good motor overall so I am not giving up on it. My dad had the carb rebuilt the summer before I got the motor (4 or 5 years ago). It ran great after that rebuild, but the next season when I got it is when all my issues started. The fuel pump cap was cracked and I had that replaced. Then I had issues with the cheap fuel line/bulb assemblies. When I finally got those issues fixed the motor would start ok and idle ok, but would never run full throttle. It would lull or surge at full throttle and I estimate it was never reaching more than 1/2 to 3/4 rpms that is should run. In addition to limiting rpms, the motor was very slow to build to the top rpm range I could get...very slow. But, I kept thinking it was from lack of use from when my dad had it. So, I ran several tanks with sea foam mixed in and installed new plugs. Essentially the performance never improved.

This season I was pleasantly surprised that the motor started easily and idled great but it still had the high end issue. Until this weekend when all of the sudden it was very hard to start and when it did it was missing and spitting and ran generally horrible. Took it out one more time to try and couldn't start it at all.

So, with lots of reading on here, and a healthy dose of youtube videos, I tore the carb apart last night. I will post some pics below and would love to hear if you guys are seeing anything I'm not. I was shocked to find the bowl and general carb body fairly clean and no sign of varnish or sticky residue. However, the idle port packing washers were completely deteriorated and I have yet to get all of them out of the threads. I'm thinking a carb dip soak might help?

I also noticed the brass jets are whitish in color. They almost look and feel like ceramic or something non-mettalic. Is this normal? Will that affect fuel delivery? The jets themselves didn't seem to be blocked. But, when spraying out the carb with cleaner, notice the stuff in the bottom of the yellow plastic bowl. I think this is mostly from the washers mentioned. But, I am wondering if it could also be from the black fuel lines? I am not sure if the lines on the motor are ethanol resistant. How do I know if they are or not? I am considering replacing anyway just to be sure.

Last question, I can barely see into the intake with the carb removed. It looks like there is a black buildup of something in the intake. I can't get a good pic of it, but is that normal? I'm scared to try to clean that bc I think loosening the buildup would just push it into the motor. Any suggestions on what I might be seeing?
 

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racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,044
Test for good spark. Spark must jump a gap of 1/4" on both leads for motor to run properly.
 

htr2133

Seaman
Joined
Jun 2, 2011
Messages
74
Btw, after I rebuild the carb and put in new plugs this week, if the motor still will not start and run correctly I will be turning attention to the ignition. Kind of scared of that but feeling brave after realizing the carb wasn't as intimidating as I feared.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,044
Check compression too.-----Many folks pick on the carburetor first for some reason.---Not sure why.
 

htr2133

Seaman
Joined
Jun 2, 2011
Messages
74
Thanks guys, is there a place I can rent or borrow the tools for a compression and spark test?
 

htr2133

Seaman
Joined
Jun 2, 2011
Messages
74
Also, the owner of a marine service business told me last year when I explained the high-end issue that I should check the thermostat. He said if the engine isn't reaching optimal operating temp it could cause issues. I ran the motor for 10-15 min. and I could hold my hand on the block and head for 5+ seconds. He said that was a sign of a bad thermostat. Is this correct and does that explain the surging and limited rpms? It sure seems like a fuel delivery issue with all of the other fuel related problems I've had. But ignition would be my 2nd thought. I don't think cooling would cause the issues I have experienced, but I defer to the expertise of the forums.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,044
????????---These motors have come from the factory with a thermostat since about 1960 !!!!!!!!!!---The tall tales just keep coming.
 
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