Problem with 1977 Mercury 150 power of tower

[Bke12345]

Alright, iv got a headache of a project needing help with. I bought a boat and motor that doesn’t run. A 1977 Mercury 150 6 cylinder 2 stroke power of tower and I already put close to $800 into it so I guess there is backing out now lol. New stator, rectifier, New engine side harness and boat side harness, new starter, New starter Solenoid, rebuilt all three carburetors and rebuilt fuel pump. The CDi switch box that Is on the motor is no good so I have to replace that. I have new plug wires and plugs so yea I have done a lot so far. I have 2 questions. First question is sometimes when I try to start the motor by turning the key then I will try to turn the key off The starter will continue to turn and I have to disconnect the battery and I don’t know why. Second question is before doing so if anyone has a thought of what this can be, i’ve done a compression test on all six cylinders and I’m getting a reading of 65 on #1 - 35 on #2 - 90 on # 3 - 110 on # 4 - 115 on # 5 and 111 on # 6 Does anyone know if this could be a blown head gasket cause the first 3 are low compression or do I have a worse problem?

 

[jheron]

There is no head gasket, the cylinders 1, 2 and 3 are likely punched and need machine work and probably over sized pistons. You will need a shop that can bore a blind hole to get them machined.
Its a shame you threw all that money at it before doing a compression test.
Cheers,
Jon

 

[Bke12345]

Hey I do appreciate the feedback. When I bought the Boat it came with 2 identical nonworking motors the one I was working on and found this out was currently on the boat and the other motor I was using parts off of it not knowing if it was a good motor or not