1990 Johnson 150 GT Loss of Power

[Alpinegold]

I had previously worked on this issue back in end of May but due to work constraints had to back off.

I have a 1990 Johnson 150 GT on a 19' Nitro. I have having 3 issues. Starting : When trying to start it after backing boat down boat ramp, it doesn't start. I pump bulb, tilt motor down and push ignition key in when starting it. The primer is working correctly. Now get this, I pull boat up on level surface, motor starts. Motor starts at home with ears on. I also have throttle marked so it positioned correctly on cam. Once started, it will start all day. This happens every time I go to the lake.

When I attempt hole shot, motor bogs down and it will not plane. I put motor in neutral, rev it up and then it will plane up and I'm on my way going to 55 mph. I have replaced spark plugs. Once I get boat planed up, I can generally come out of the whole the rest of the day . The same process happens each time I go to the lake.

Some times when I am up and running, the motor will get a surge in power and the boat will pick up an additional 5 to 10 mph with out moving the throttle.

Like I mentioned, the last time I attempted to work these issues work constraints got the better of me but I got all the time now and would really appreciate any thought and direction.

Thank you,

Alpinegold

 

[glenn property of pam]

start with a basic health check. Test compression and spark (using a spark tester on all cylinders). sounds like the carbs need to be serviced which is why it will start when there's no back pressure on the exhaust but its better to start at the beginning with basic tests.

 

[emdsapmgr]

Any time you get a random surge of power, it's likely that the 6th spark plug started firing. Check for spark-but be sure you do it after the engine is well warmed up. A cyl drop test is good for checking spark, or use an inductive timing light to show plug firing.

 

[theoldwizard1]

I won't guarantee a fix, but "it can't hurt" and it is not too expensive.

Replace all the fuel line, both inside and out, including the primer bulb. Make sure to use the correct clamp.

 

[Alpinegold]

Thanks guys. I'm on it.

Alpinegold