TOPIC: '59 Johnson Fat Fifty Carb Rebuild

Having a problem getting the carb rebuilt on my Fat Fifty.

I bought a carb rebuild kit through iBoats for it, but it doesn't add up. At this point, since the engine was messed with by the previous owner, I'm not sure what to believe as correct.

The kit I ordered: www.iboats.com/Carburetor-Kit-for-Johnson-Evinrude-382057-GLM-40540-Sierra/dm/view_id.174124

The drawing in my service manual shows there should be four washers and seals on the adjustment knob shafts. The carb only has one of the four right now. See manual:



Other things about this carb compared to what they show in the book makes me wonder if it isn't the correct one on there.

Does anyone who really knows these engines know which is correct?

Mine before disassembly:

The carburetor in your photo is the correct one for the Fifty. The later 75HP carbs look the same, but there are some minor differences. The throttle cam on the Fifty is different than all of the other years, so that is the easiest way to tell. The washers you are referring to are the "packing washers" that are intended to make an air-tight seal around the stems of the low speed / idle needle valves. The kit you purchased is also the correct one, if the parts appear the same as the one in the website photo. The packing washers are usually either paper or plastic - and there is usually 3 or more washers per needle (6 or more) included in a kit. What happens is that when the brass compression nut is tightened down, it smashes all of the washers together, and they then appear as one thick washer. The old packing can be a bitch to get out of the carburetor body. A hooked instrument, like a dental scraper, or sometimes a large sheetrock screw can be used to coax the old packings out. The carb kits usually don't come with any information, so you would be wise to purchase a repair manual from selock, or go onto Ebay and find a vintage OMC manual. You really should have one if you don't already.

A couple more important notes - you MUST replace the old float in your carburetor if it is a dark reddish color, or if it appears to be distorted, or gas-loged. The new cork floats are coated with an alcohol proof coating, and they appear to be light blond/tan in color. The old floats absorb fuel and become too heavy to work correctly. If the float isn't functioning correctly, the engine will never run right. Your best bet is to either go on Ebay for a NEW float (not NOS - as they probably aren't alcohol resistant) or to find a new one online somewhere. Just be sure that it is a new production part with the right coating. The next thing to pay close attention to is to get the main jet boosters centered EXACTLY in the two venturis before tightening the mounting screws.

Good luck with it - thy are a very straight forward carb - just be sure everything is clean and blown out with compressed air before assembly.

Thanks for your tips Bruce, they were helpful in reassembly! My dad and I finally got it reassembled the other night.

In going through all the spare parts I received with the boat/engine, I found what I believe are many of the original carb components, so I think the previous owner ended up rebuilding it himself. But, we put all the new parts I got in anyway for peace of mind, even though I saved the ones we took out just in case. I found the original float as well, which was exactly as you described, red in color. The new one was a little tricky to work with because it has a hole in the bracket to hold a small spring clip for the needle, which was tricky to get on and the original didn't have that. I'll admit, the float in there is the one that he put in, my rebuild kit didn't come with one and that one looked good, tan in color. Do you think that hole/clip is a sign of a new design one? In the NOS one I found online, it also doesn't have the hole/clip like my original one has.

I did purchase an original Johnson service manual for this engine from eBay which has awesome clear diagrams in it, so that was a big help in reassembly. I have something like a Haynes manual for the engine, but it's somewhat generic and the pictures aren't clear for every detail. I'm still in search of an original owners manual for the engine, just so I can have full documentation on this engine, but the only one I saw for this specific model was like $80.

We did pull the main freeze plugs, but I suspect he had those out too. It was very clean in there and required very little clean up.

Here's a pic of the finished product, hopefully ready for installation:



Now just hoping for some warm weather soon so I can actually get to painting the engine parts!

Congratulations on getting the carb back together. If the float had a clear coating and tan (natural) color, it is most likely OK. The newer floats do have a hole for the needle valve retainer. This spring is intended to pull (by force) the needle valve open in the event that the rubber tip on it becomes stuck to the valve seat. A stuck closed valve would prevent gas from entering the carb. The original needles were all metal with no rubber tip , so there was little chance of them sticking closed. the rubber tip needles seal better to prevent flooding - that is why they changed them.

Thanks again, Bruce. I'm pretty sure this is a new type float then.

I do have a question about the jet boosters. I don't recall any adjustment in them, the screws went in and that was it. I did put them in and roughly center them before tightening, but I didn't measure anything. How should these be perfectly centered?

I am getting ready to rebuild the same carb. I have never done one before and I am hoping to lean on this fine community for guidance. My motor sat for 14 years before I got it running last fall.

Congrats on rockin the rebuild Sunline Fan.

As you saw - the boosters are held in place with a couple screws. There is a bit of wiggle room for the booster to move off center of the venturi - so as the screws are tightened, one has to hold the part in the correct position. OMC had a special tool that centered the boosters while the screws are tightened ( I actually have one somewhere) but that isn't needed. You can use a caliper, dial indicator, precision micro rule, or just eyeball it best you can.

Bruce Gerard wrote:

As you saw - the boosters are held in place with a couple screws. There is a bit of wiggle room for the booster to move off center of the venturi - so as the screws are tightened, one has to hold the part in the correct position. OMC had a special tool that centered the boosters while the screws are tightened ( I actually have one somewhere) but that isn't needed. You can use a caliper, dial indicator, precision micro rule, or just eyeball it best you can.

Thanks Bruce! I will pull it apart and make sure they are centered with calipers.