1976 Merc 402 blown up?

[bassfishindy]

Hello,<br /> I have a 1976 merc 402. I let a friend use it and he drove about 3 minutes and the motor died and would not start. he took it to a shop and they ran a compression test. the top cylinder was about 60 and the bottom was 120. i hooked the hose to it and could pull start it. when it does run, it has to be choked and back fires out of the exhaust. as soon as the choke is off, it dies. there is no water circulating either. I am pretty sure the impeller is toasted. this motor has been perfect up until now. Is it dead?

 

[studlymandingo]

Re: 1976 Merc 402 blown up?

Top cylinder compression is not good. Try doing a decarb as described in this forum. Also spray some Deep Creep into the affected cylinder, there is a small chance you have seized rings.

 

[bassfishindy]

Re: 1976 Merc 402 blown up?

would it be possible for me to transfer the cables from my 1976 402 model and use them on a 1979 merc that is not a 402?

 

[phatmanmike]

Re: 1976 Merc 402 blown up?

yep

 

[bassfishindy]

Re: 1976 Merc 402 blown up?

I just noticed another possible problem. there is half of a pin missing where the wiring harness plugs into the side of my motor. will this have anything to do with my starter acting up or the back firing? I want to try to do the decarb, so i would like to be able to turn the motor over with the starter. It is a new starter. thanks