Johnson 70 hp

[Tpearce]

I recently went to run my boat since having carberator problems. In doing so I met up with a friend who had purchased an older bass tracker that is equipped with a Johnson 70. He told me that no one has been able to tell him what is wrong with it and it has now got my curiosity stirring.

His Problem:

The motor will not start unless the prop is out of the water. Once it cranks, you can lower it into the water and take off and run great. Any ideas??? I can't stop trying to figure it out.

 

[grsmnky1]

Re: Johnson 70 hp

Have your friend check his compression. If low the backpressure of the water could be the cause. Also check the timing.

 

[jtexas]

Re: Johnson 70 hp

What year motor?
Is it a cold start problem, or warm start, or both?

Lack of backpressure on the underwater exhaust, is why it starts with the prop out the water.

Reason it doesn't start with the lower unit submerged, is that something's wrong with it. Could be cranking too slow, could be bad compression, could be a choke malfunction, or idle speed setting, or mixture setting, or....many things.

I would recommend you take better care of yours...when a problem arises, fix it. Whatever it is, it's going to send that motor to an early grave.