View Full Version : Problem with 90hp mercury 4 stroke.

14-10-2018, 12:19 PM
I have a 2014, 90hp four stroke Mercury with 200hours on it.Recently I slowed down to go under a bridge and on acceleration it just died as if it ran out of fuel. On examination it had zero compression. The drive cog to the cam shaft was loose. I have spoken with 4 experienced Mercury mechanics and they all said that they have never heard of it before. It did have a minor harmonics problem that I fixed. Any comments on why it happened would be much appreciated.

14-10-2018, 12:24 PM
Probably need a bit more in-depth investigation to determine how bad it is, might not be real bad, but it might be.

18-10-2018, 08:52 AM
Thanks for your input mate.

20-10-2018, 08:41 AM
Is it an interference engine?hopefully not.
If not it might be ok. Zero compression because your valves arenít opening/closing correctly.
Woukd someone have taken cam drive cog off prior and not put in back on correct? Does it have a key or tapered?

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20-10-2018, 10:27 AM
Could be anything, but with the limited info, it's just stabbing in the dark.

21-10-2018, 10:06 PM
No internal damage. I'm more concerned as to why it happened. Could be bad if it died at the wrong time. I was lucky I had a mate with me to tow me back but that might not always be the case.

22-10-2018, 07:22 AM
Bit hard to follow this, are you saying the engine is OK? what about the no compression business? if you are just asking why something came loose, then it's just a case of sometimes things happen for unknown reasons, never torqued from new? was moved during routine service?