Johnson 1973 50hp motor not running to speed...

[nickdiana]

I have a 1973 50hp Johnson motor that is running about the speed of a 10hp. I recently changed the fuel filter, ran a compression test for the spark plugs (about 150lbs each cylinder), cleaned the carburetors (2 of them), synced the carb (sync and link), got new gas, and made sure the key was in the right position.

NOTHING! Does anyone have any ideas for me to check next? I really want this boat to go fast but don't want to put any more money into it if it is going to keep failing b.c it is not worth the money put into it.

Thanks.

 

[jtrom]

Re: Johnson 1973 50hp motor not running to speed...

Had same problem in my 74 Johnson 50.....turns out one of my carbs was gummed up and it was running on one cylinder...what do your spark plugs look like after you have run it?

 

[nickdiana]

Re: Johnson 1973 50hp motor not running to speed...

spark plugs are getting enough compression and they look fine after running it. I am getting about 150lbs of pressure, as well as the carbs are super clean - almost new looking. I have read a lot of forums and am wondering if I should drill a few holes along the bottom and top of the hull and attach a shop vac for a few weeks? It seems like the only option at this point besides throwing the boat out. Any suggestions on what to do or actually how to do this?

 

[bktheking]

Re: Johnson 1973 50hp motor not running to speed...

In your diagnosing you haven't stated if you actually checked for good spark on both plugs, just that the "look good after running it". Hook the leads up to a spark plug tester to verify. It also wouldn't hurt to run a timing light on the wires to watch the pulse.

 

[nickdiana]

Re: Johnson 1973 50hp motor not running to speed...

compression is great, spark is great, wires are great. Everything has been checked by a johnson dealer and the motor seems to be running fine. Someone recently told me that the hull might be saturated with water - so i might have to either drain it or get a new boat? not sure what to do - trying to find a manual right now.

 

[Andy in NY]

Re: Johnson 1973 50hp motor not running to speed...

compression is great, spark is great, wires are great. Everything has been checked by a johnson dealer and the motor seems to be running fine. Someone recently told me that the hull might be saturated with water - so i might have to either drain it or get a new boat? not sure what to do - trying to find a manual right now.

if the hull is full of water, "draining" is isnt going to help. chances are the stringers, deck and transom are rotted and the foam is holding in all that water. "draining" it would be like throwing a lysol bleach wipe into your pool to treat it.


what kind of performance are you getting? it would help for you to list things like

1) load (people, fuel, toys, snacks, strippers, elephants, etc)

2) what length and hull design (v, tri, toon, etc)

3) top speed (gps, not speedo) & rpm

4) prop size