1968 johnson 6 hp slow

[nwcove]

the motor came from the factory with a 2 blade 8 x 7.25 " prop.

 

[letitroll707]

Is there a better prop we can put on it and do you knpw which one it is?

 

[Tim Frank]

.... dont know what im missing to get this motor running faster like it should. Please help.

All you are going to get from most of us is the best advice we can offer, based on a lot of cumulative experience. So far, that's what I have seen posted. Maybe you need to go back and read the thread again.
You seem bound and determined to find the magic bullet that will turn this motor from a 6 hp into something that it isn't....like maybe a 15 HP.
We've told you that there is no elixir....not sure what else there is to say.

IF you want to try swapping out props to try and increase performance, you will need a way to measure RPM, and probably you should post in the prop section because you'll get a more focused answer. But either way, any gain will be minimal, and still won't get you to the Promised Land.

Good luck.

 

[dude11]

I have a 6hp.Johnson on a 14ft.jon as well.I think your getting all she's got.Mine ( with a passenger) both weighing about 185lbs.runs 7mph on a gps.I don't think it'll do more.I mostly river fish,so that's fine for me.As stated maybe an upgrade in hp.is your only hope.

 

[letitroll707]

I appreciate all the help have learned a lot about this motor and some new things to try and trouble shoot for doing repairs. Thank you everyone for your help sorry if I annoyed anyone with my questions just trying to learn and make sure my motor is running like it should.

 

[kbait]

Did the drop test pull wire off top plug it dies pull off second plug still runs what do I do?

Top cylinder is combusting/running, bottom cylinder is not. You need to find out why the bottom cylinder isn't firing. Possible causes:

-Poor compression in bottom cylinder (bad head gasket or scored cylinder). You can check by pulling the recoil rope slowly (plugs installed). You'll feel 'whoomp, whoomp' twice per flywheel revolution if both cylinders have compression.. the 'whoomps' should feel even between cylinders.

-No/poor spark due to a) fouled spark plug (try swapping plugs, or install new Champion J6C's gapped to .030") or faulty coil/condenser/pointset/plug wire on bottom cylinder circuit. If you have adequate compression, good spark (1/4" in open air) with new spark plug and it still doesn't fire, then

-Check reed valves on plate behind carb. If reeds are bent/broken for bottom cylinder, fuel/air mix cannot 'draw' into cylinder.

Good luck!

 

[Tim Frank]

If you are getting 5 MPH with 2 adults in a 14' boat, that's not bad.
If you want ~ 20 MPH, you'll need to upgrade your HP to at least 15.

You should still make sure whether you have a problem or not.
Try the drop test at a high idle.... sometimes if you do the test with a motor that DOES have both cylinders firing OK, if the speed is a tad too slow, it can cut out on one, but not the other.
Test the spark with a proper spark tester.

^ ^ ^ ^ ^

 

[racerone]

Was given a 1969 Johnson 6 hp yesterday by a dealer.----------------Will tear it apart and rebuild it.----Hoping it will do 20 mph so I can get rid of my 15 hp motors.