72 johnson 50esl72c 50hp no start

[kingblazer84]

So boys been searching and reading for the last couple days and no such luck with an answer. A little back story, bought a 1972 electric shift 50hp johnson outboard has 120psi compression swapped it onto my 15' boat great right? haha Change the impeller as I have worked on alot of boats for years but only inboards never outboards, and its always nice to put a new water pump in when you dont know the history of the engine. Everything on the motor is super clean for the vintage, only run in fresh water never salt. Motor has 1 new carb on cyl #2 and the top one was rebuilt.

So after changing the water pump and leg oil, proceeded to take the boat out for a maiden voyage, ran up and started and idled like a champ no issues, even went into gear nice and smooth. Pushed away from the dock and started to power up and had it going but it would not reach full rpm after about 6 or 7 mins of running and not planing I got angry and decided to pull back to the dock. about 10 feet from the dock the motor on low idle in gear just dies conks out, wont start then next thing I see is SMOKE pouring out of the bonnet. So I pull the lid meanwhile drifting into shore, have a look and the cylinder head is smoking (Lack of cooling) and burnt the temp switch wire in half. So I get the boat back to my shop and start the tear down, I figured that the thermostat was stuck closed, removed the head and replaced the old rusty thermostat and 2 way pressure valve along with new head gasket and top cover gasket. Check compression motor is still putting out 120psi but will not fire, had a look at the coils they are starting to crack slightly on the outside, just wondering where to go from here?

Also installed the tell-tale setup in this motor with the top end rebuild I just did as well so hopefully if I get this thing going I can watch the water get into the head, there was a nice constant stream of water coming from the exhaust housing when it was in the lake though so I know for a fact it was pushing water.

Cheers

Nick

 

[kingblazer84]

checked ignition system power pack it is supplying power properly to the coils, tested the coils found the resistance between the ground wire and the plug wire end are low at about 2000 ohms, and both shells have cracking so I will be replacing those and see if this helps the no start.

 

[kingblazer84]

well the coils fixed my no start issue, but still not getting water to the cylinder head, its coming out of the exhaust well but not the telltale. Ill remove the lower unit and have a look and see if the pipe is not mating into the seal properly is there any other fixes for that pip issue?

 

[kingblazer84]

Well she pumps water now, the water pickup tube was bent when we reinstalled the lower unit. I was able to bend back and reinstall properly and tested ok, but this thing still has a pretty good miss, gonna toss new plugs in it and give it a go any other ideas??

 

[kingblazer84]

Tuned up the idle jetting on the carbs for her to idle nicely and high idle nicely, now she still has a slight miss but not bad does anyone have a good tutorial on how to time these old johnson outboards?

 

[Bosunsmate]

track that miss down, as if a cylinder is running lean you will sorch her
put a couple of fingers into each carb in turn and see if that can isolate it down to one cylinder

 

[kingblazer84]

yah ill take a peak this weekend and see if I cant narrow it down, also going to run a new tank of 50:1 mix gas 91 octane and see if that helps as well

 

[kingblazer84]

well she will rev up in neutral but not in gear she only does about 15mph wont get up on plane, I think the motor is pooched anymore ideas on how to get this thing to get up and go?