GT or not GT

[lockett]

Hello all, thank you for the add. I have what i think is a 1983 Johnson GT150. I was told that that the power head was probably changed due to the missing holes in the flywheel. The original owner was sure that is was an original 83 GT that had never been overhauled? I have add a few pictures to see what you think. I'm not worried if it is not a GT it pushes my boat 60mph and that's all I need. Just thought I would get a clear answer. Thank you again.

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[omcforever]

Purdy motor,,,,

[omcforever]

1983 (1st year GT/XP 150 produced) did have a 10 amp charging system so the flywheel will be different from later GT/XP motors (1984 on) which had a 35 amp system. Later flywheels where finned and vented per say for the heat created by the charging system. 1983 GT/XP should have 1 5/16 throat carbs(stamped on front of carbs) and have high compression heads #329772/329773. The transom data plate matches the block welch plug so I would say you have a GT 150. Whoever told you it isnt a GT due to missing holes in the flywheel doesnt know what they are talking about. Very stout motor(about 160ish HP.)

[lockett]

Thank you for the correct info. I hate Jack leg shade wrench heads that see one thing and think the know it all. Here is a pick of the stamps on the carb.
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[omcforever]

Yep,,,GT150 motor...take care of it since they are getting scarce. Keep oil mixed at 50:1 for everyday use and if you do decide to dog it or long runs, run 40:1. Very clean motor. (Before anyone jumps me the 1983 didnt have VRO yet)

[lockett]

Yep,,,GT150 motor...take care of it since they are getting scarce. Keep oil mixed at 50:1 for everyday use and if you do decide to dog it or long runs, run 40:1. Very clean motor. (Before anyone jumps me the 1983 didnt have VRO yet)

Thank you guys for the help. The compression is low so I was planing to build the power head. Any suggestions? New pistons rings? Also what should i go back with?

[ChampioNman]

That's not what he meant the stamped numbers are on the face of the carbs you'll need to take the air box and back plate off to read the numbers. What are the comp numbers?

[omcforever]

Front of carbs behind air silencer cover base.

[lockett]

Ill pull mine and check it.

[lockett]

Bad, 85 in all 6.

[lockett]

Front of carbs behind air silencer cover base.

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[lockett]

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Found it.

[omcforever]

Bad, 85 in all 6.

Not bad. Nice and even. Perform a de-carb and re-check. I have seen em 85-100 or more. Big thing is they are close and even. Decarb and let her rip...