1968 20hp Johnson starting problems

[Parenouf]

Good evening guys, I've just brought a 1968 20hp johnson which was seized. I got it home and managed to un seize it and got it started and running for about 15-25minutes, thought great I've sorted it. And put in my shed for the night. Today I took it out and went to start it but no joy it would run for about 10-15 seconds then die now I'm losing patience and have put it back into shed before I lose it. I'm thinking it's a carb. Problem is it? Or is it more terminal? The thing that's got to me is that it ran fine yesterday!

 

[kfa4303]

Re: 1968 20hp Johnson starting problems

What fuel/oil mix are you running? I run 24:1 in my '66 20 hp, but you could go as lean as 50:1. Did you run it in a test tank, or on muffs? These old motors can't be run on muff and cool properly which may lead to over heating. A good carb cleaning couldn't hurt either. You can get a carb kit right here at iboats for about $20 US. Here is a handy link to get you started. Assuming the compression, is good, all the rest can be fixed with ease.

http://www.leeroysramblings.com/johnson_E-FD_15_18hp.html

 

[Parenouf]

Re: 1968 20hp Johnson starting problems

Hi I ran it in a test tank, and fuel mix is approx 22:1

 

[kfa4303]

Re: 1968 20hp Johnson starting problems

Good. Be sure to use Champion J6C spark plugs as well. You may have an ignition component failing as the motor heats up ,which is not uncommon. Thankfully, you can rebuild the entire magneto yourself by replacing the points and condensers and gaping them to .020". Here's a great link on how to do the job. The original OMC coils were prone to failure and may also need to be replaced. However, if there are no obvious cracks or scorching to them, they are probably ok. You can get both the tune up, carb kits and coils right here at iboats for about $20 each. Don't give up on her just yet. Once she's up and running you'll have a great, unique motor that makes lots of power for its relatively small size and low weight.

http://www.outboard-boat-motor-repa...on 3 HP 1952-1967 Ignition System Tune-up.htm

http://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1968&hp=20&model=FD-22M

 

[Parenouf]

Re: 1968 20hp Johnson starting problems

Not gonna give up! Carb come off last night damn good clean and new fuel line from pump to carb. Old one was breaking up gonna try start today (it was a bit late when I finished) fingers crossed :}

 

[Parenouf]

Re: 1968 20hp Johnson starting problems

Carb given a damn good clean and hey presto engine runs like a dream. am now gonna put her in for a service at a qualified workshop so she's perfect (I'm over the moon that I saved this old engine from breaker)

 

[AlTn]

Re: 1968 20hp Johnson starting problems

glad you got'er goin'

 

[kfa4303]

Re: 1968 20hp Johnson starting problems

Great news Parenouf! Amazing what a little carb cleaning can do. Happy boating. Cheers! We'd love some pics of it on the water

 

[Parenouf]

Re: 1968 20hp Johnson starting problems

Would the angle of tilt have an effect on the cooling of the engine as when it was tilted slightly it got hot and cut out but when it wasn't tilted she ran fine at full power?

 

[Parenouf]

Re: 1968 20hp Johnson starting problems

I think I've found the problem !!!! NO THERMOSTAT !!!!! Oh bugger

 

[kfa4303]

Re: 1968 20hp Johnson starting problems

No worries. A t-stat is only about $15 US and just drops into place. I don't know why, but lots of people remove them in under the misguided notion that they aren't needed. If the motor was designed with a t-stat, it should use one. The motor should pump water at all times, as long as the lower unit is properly submerged. If the t-stat doesn't fix the water pumping issue, I would drop the lower unit and inspect the water pump (impeller). Here's the t-stat and grommet.

http://www.iboats.com/mall/partfind...4092=18&gd_search_14093=&session_id=505329551
http://www.marineengine.com/parts/j...&manufacturer=Johnson&section=Powerhead+Group

 

[Parenouf]

Re: 1968 20hp Johnson starting problems

Cheers I'll look into it

 

[Parenouf]

Re: 1968 20hp Johnson starting problems

I put the engine back in the test tank and she ran fine I was able to keep my hand on the cylinder head, I also loosened a nut on the thermostat cover and had water spurting out so I'm not sure now what caused the overheat but she now seems fine but I'll still order a new thermostat :~