74 50hp johnson, What now?

[jsalz]

I have been having problems with this motor for over a month. At one time we could get 25 mph gps but now can't get enough rpms at wot. Here is what has been done.
Replaced faulty fuel pump.
Took apart carbs, soaked, blew out with compressor and rebuilt with new kits.
Replaced ignition coils as old ones had some cracks.
Checked compression and got 130 and 135.
Good spark on both plugs now.
There is a small ding in prop but not huge.
I have not done a link and sync yet.
Motor will scream in neutral with idle lever but falls flat under load.
Again, this motor did run well a while back but only periodically.
Help!

 

[jsalz]

Re: 74 50hp johnson, What now?

Also, primer bulb stays hard and nothing changes when pumped while running. I also checked reed box and none were broken and all moved freely.

 

[tashasdaddy]

Re: 74 50hp johnson, What now?

did you do all of this, and use Joe Reeves settings for the slow speed needle. how can you expect it to run fine without doing a link n sinc.

 

[jsalz]

Re: 74 50hp johnson, What now?

I did follow Joes guide for the low speed needle but I don't see how that would affect RPMs at wot. I will do the link and sync next. I don't have a timing light yet. The spark advance has never been touched though. One other thing that I did notice is that with the motor stopped and throttle full forward, I can turn the prop back and forth about 1/4 turn by hand. Is this normal?

 

[tashasdaddy]

Re: 74 50hp johnson, What now?

normal. if you did not pull those high speed jets the could have reclogged.

 

[jsalz]

Re: 74 50hp johnson, What now?

I did pull the hs orrifaces. They were clean but I made double sure. I did find a small plastic shaving in one bowl. Thoght that was it but nope.

 

[jsalz]

Re: 74 50hp johnson, What now?

normal. if you did not pull those high speed jets the could have reclogged.

Could you explain reclogged? How? I just cleaned and rebuilt everything.

 

[F_R]

Re: 74 50hp johnson, What now?

How much power loss do you have? 1/2 or more? That would indicate running on one cylinder.

If that is the case, remove and ground one spark plug wire and see how it runs. Then do the same with the other one. The one that makes no difference when grounded is the one that is just going along for the ride. Now you know which cylinder to zero in on.

And stop revving it up in neutral. Sheese!

 

[jsalz]

Re: 74 50hp johnson, What now?

How much power loss do you have? 1/2 or more? That would indicate running on one cylinder.

If that is the case, remove and ground one spark plug wire and see how it runs. Then do the same with the other one. The one that makes no difference when grounded is the one that is just going along for the ride. Now you know which cylinder to zero in on.

And stop revving it up in neutral. Sheese!

Can I just try to start it on one plug or do I need to pull the plug wire while running? If I need to do it while running, do I really need to ground it or can I just pull it. I dont really want to play around with voltage that high.
Also, I only rev it in neuatral in short bursts, not maintained.

 

[tashasdaddy]

Re: 74 50hp johnson, What now?

never over 1500 rpms, short or long. good way to get a face full of connecting rod.

 

[jsalz]

Re: 74 50hp johnson, What now?

OK, I'll definately stop doing that. What about removing plugs while running vs. starting on one and do they need to be grounded?