Johnson 150 Won't Start

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
iowan75
Posts: 1
Joined: Fri Jun 08, 2018 2:25 pm

Johnson 150 Won't Start

Postby iowan75 » Fri Jun 08, 2018 2:28 pm

Trying to start our 1990 Johnson J150STLESB 150hp Outboard Motor. Using timing light, five out of the six cylinders are misfiring with one firing all the time. What could possibly cause this problem?

jimh
Posts: 11673
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
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Re: Johnson 150 Won't Start

Postby jimh » Fri Jun 08, 2018 4:56 pm

Ignition spark timing is controlled by a sensor that detects magnets in the flywheel. The sensor is part of the flywheel stator assembly. The sensor is connected to the Power Pack. To check the operation of the system, check the various elements in this order:

  1. all connections in the circuit
  2. Power Pack
  3. spark timing coil in stator assembly
  4. flywheel magnets

The service manual will give details. Attempting to make repairs on an engine without the factory service manual on hand will put the repair process at a big disadvantage. Get the factory service manual if you want to work on your outboard engine yourself.

The factory service manual should offer advice on diagnosis of spark ignition problems.