4R73C Johnson 4hp maintenance, need advice on some issues

The first signs of spring is showing up here in Arctic Norway, so I got my 1973 Johnson 4hp out of the shed and had a look at it. This is a motor I got last year to use with my S.I.B for some fishing. And used it from July to September about every weekend.

Anyway, here is what I found and what I have done with it.

1. Gear oil. I don't know when that was last changed. So I changed that. There is no level hole to open on this motor. Just the one screw, so I open that and only water came out, followed by a few black drops of oil...bad sign. But Okay, I filled it up with new gear oil that the local boat dealer recommended for me.

2. Last year the starter rope snapped on the first day out, so I had to change that. But I only found starter rope that was to thick. Well, it sorta fit, but after that the rope would not rewind properly. Probably become I damaged the recoil spring become frankly I had not the faintest clue what I was doing...got some nice help from Rick her on the forum though and now I now how to do this. So starter rope changed to correct diameter rope, and recoil spring also changed, and that whole assembly lubed up

3. Carburettor: The motor don’t really go that well. That is it starts after some fiddling with the choke, and adjusting the throttle lever back and forth to a setting it likes. But it does not run well on low throttle, and I have one question here:

Dies this model really have an Idle gear? It has Stop, start and then throttle...as soon as I pull it back towards start, it stops...

Anyway, what I did with this today was to set it up for a run in a barrel of fresh water. Sprayed some CRC carburettor cleaner straight into the air intake of the carburettor (like it says on the spray can). Then started the engine and revved it up and sprayed in more of that stuff...the water soon hat a lot of black gunky spots floating on top...but also a fine film of oil...uh oh!

4. Opened the gear oil screw, and found white foam inside...so water is coming in. I then proceeded to drop off the whole lower part (the part under the cavitation plate). And the seal that sits under the impeller looked a little worn. So I have ordered a new one. Actually ordered a new set of every seal and O-ring that connected with the gear, including the O-ring for the oil cap screw...so that should take care of that. In the process I discovered that the drive pin that prevents the propeller shaft to spin freely inside the propeller (if it does that the prop don’t turn) was snapped in three. Hats a $1.11 part so I ordered that one too...

Anyway, the seals for the drive and propeller shafts is identical. But I think it may be difficult to get the old ones off, and insert new ones. So any advice here is appreciated!

5 Impeller: looked like it was new, so I left that one in.

6. Spark plugs...changed those.

7. Zinc anode: There is none of these on the motor that I can find. Nor is there any on the parts lists. The previous owner used it in fresh water only. But I use it in salt water. Should I drill bolt holes in the cavitation plate and install one there? (someone said that was not a good idea, better find another place for it). Advice appreciated...

8 Anything else I should do with it before the season starts?

Re: 4R73C Johnson 4hp maintenance, need advice on some issues

don't use that carb cleaner except to clean the carb when it's removed from the engine as you will be removing the oil film from the crank and rod bearings as well as the rings and cylinder walls. The carb cleaner only goes through the carb throat and doesn't clean it internally at all.
From the sound of it, you need to remove, disassemble, and thoroughly clean the carb. Inspect the main and idle mixture needles for grooves, broken points, etc. I'd go ahead and install a carb kit, but that's up to you.
Lower unit: looks like 2 seals and a large o-ring is it. By removing the gear case head and bushing assm., you can remove that seal by supporting the head on a couple of wood blocks and knocking it out from the back with a punch. Replace the o ring as well. I'd guess some sealant is called for around the o ring.The driveshaft seal may require a seal puller to remove. Marineengine.com doesn't list a part # for one, so I'd make doubly sure I had one that would fit before I pulled the one now in there.
The water pump impeller I'd replace now since you're there especially since you are using it in salt water.
Anode question I don't know.

Re: 4R73C Johnson 4hp maintenance, need advice on some issues

Allready used that carb cleaner. So to late :-|

But I have ordered the carb kit, so I guess not to much damage done as I won't use the motor before the lower unit is properly sealed.
Else thanks for taking the time to help me out.

Re: 4R73C Johnson 4hp maintenance, need advice on some issues

Love these motors man, sooooo worth the time and money to keep em running.