1968 40hp johnson wont move in the water.

[Nhayes0027]

I have a 1968 40hp johnson. Rebuilt the carb and now it runs great! How eber, Prop spins well in forward and reverse when hooked to the hose but I took it to the lake for its first test run last night and boom.. high revs with 0 movement. I was making some waves behind the boat seemingly indicating the prop was in some way moving but the boat stood still. Any ideas?

 

[ahicks]

You should be able to stand on one side of the prop with the engine in gear. One side in forward, the other in reverse.

 

[racerone]

Try another prop !

 

[F_R]

No Title

Drive (shear) pin broken?? Prop hub slipping?? Yes, it does have a rubber hub in the prop! OR, is it electric shift? That is a bit more complicated.

 

[Nhayes0027]

It is electric shift. I do believe it to be the hub and it seems out of 10 local boat service providers, none can order the correct prop.

 

[F_R]

Aha! So the problem could be in the electric shift. Or the prop. Some simple tests are required to see where to go from here. Checking the drive pin is simple and costs nothing. Checking the prop hub requires launching the boat. Checking the voltages to the shift clutch wires costs nothing and is simple if you know anything about using a voltmeter.

Don't buy anything till you know what is wrong.

 

[Nhayes0027]

Could you explain how to test these things?

 

[Nhayes0027]

The sheer pin seems to be fine. The launch as of yesterday resulted in prop spinning enough to make ripples but not enough to move the boat. The electric shift, I'm not sure on how to check.

 

[Nhayes0027]

Also while hooked to a water hose, the prop seems to go in forward and reverse just fine. Spinning in both directions as it should.

 

[racerone]

Yes it would spin since there is no LOAD on the prop !

 

[Tim Frank]

Do a search in here on "spun prop". You will find the test procedure to confirm or rule this out as the source of the problem.

 

[F_R]

Simply put, scribe a line on the plastic prop nut and another line on the prop, aligned with the first one. Run the motor (under load, on the lake) till suspected slippage occurs. Stop and check your lines. If they are no longer aligned, the hub slipped.

 

[flyingscott]

Do the hub test. Seeing ripples behind the boat when you are revving it up is more than likely the exhaust coming up.

 

[Nhayes0027]

Seems I had some wiring issues. Boat wasn't going into gear and through some wire adjusting I now have forward gear. Still no reverse but hopeful that some wire replacement will fix it.

 

[F_R]

Be VERY careful when messing with those wires. If you accidently apply voltage to both forward and reverse wires while running, something $$$$ may bust.

 

[Nhayes0027]

For an update the shift cables and every other wire in the block are corroded. After rewiring the shift cables from the block to the ignition, I now have forward but I'm still with no reverse. I assume it's at this point the shift selanoid in the lower unit. Another days project.

 

[F_R]

It doesn't have solenoids. But don't assume, check the resistance of the reverse coil (blue wire) with an Ohmmeter. And check the voltage to it also.