1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

[New Boater Brad]

Started the engine fine in the morning. Went fishing (trolling) most of day. Drove back to dock at full speed. Everything was fine untill I tried to starting it again after sitting for about 20min then the fly wheel siezed.

Pryed the fly wheel past the "hard" spot and tried starting it again and would only turn till it hit the "hard" spot again. Tried this many times with the same result.

Left the boat for a day and tried it again the next night. It turned over but had a hard time to get it started. Would start up but wouldnt run. Then finally got it run. And it seemed to run fine after coughing and sputering.

Why would the engine sieze at the same spot each time I tried to start it?

There is water coming out of the tell tale hole.. seems like the water pump is working fine.. did it get too hot??

 

[bktheking]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

That or it isn't getting oil, stop trying to start it until you figure out what's wrong, you'll just do more damage.

What is the SN of the motor?

 

[New Boater Brad]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

Hi thanks for the reply, I dont have the SN with me.. can get it later.. but its a two stroke engine and I mixed the gas 50:1 how could it be that its not getting any oil? You think the jets are leaned out to much?. I did just finish a gas tank with Sea Foam in it.

 

[bktheking]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

If it's a mix motor probably not the issue, thought maybe it was injected. Water coming out of the telltale means it's pumping, not overheating. If you have a laser thermo, start it and measure the head temp, if it starts climbing to 150+ the stats could be shot. Are you certain you added oil?

If the jets were that badly plugged you'd have a hard time getting on plane.

 

[New Boater Brad]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

Yes I added oil. Very careful about that. It ran great untill I shut it off.. and tried to start it again.

I cant understand why the fly wheel would stick in the same spot. Could there have been too much gas in one cylinder?

Would anything else cause it to stick?

My first thought was a warpped cylinder but I doubt thats it because it did start a day later?

 

[bktheking]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

Did you pull the plugs out and rotate the motor? Water intrusion could cause it. Some Merc's developed holes in the water jacket's over time and ingested water, could it be hydrolocked?

 

[New Boater Brad]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

I pulled the three top plugs, but not the bottom 4th one and it was still stuck at the same spot. I should have pulled the bottom plug.

Im not sure if it is hydrolocked.. how would I know if is.

I should mention that the weekend before I had no power at top end.. the cause a broken/corroded wire from the ignition to the coil for the number 4 (bottom) cylinder. I replaced it and it ran great

 

[bktheking]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

Run it in the water, bring it home, pull the plugs and start the motor with the plugs out (ground the plugwires). If the cylinder has water intrusion you`ll see it coming out of the spark plug hole.

 

[New Boater Brad]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

Thank you very much for the info.. the SN is A940199.

I will try that.. and if that is the case how would you repair a cracked water jacket? Does it mean a whole new block?

Is a cracked water jacket the only cause for a cylinder sucking in water?

thanks
Brad

 

[bktheking]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

No, you could have a hole in the cylinder...that wouldn't be good.
Doesn't sound like water though, i'm thinking it overheated.

 

[j_martin]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

Everybody is guessing at this point. One thing is clear, though. It's broken, and any attempt to start it can and probably will cause more damage.

It could be water leak, fuel in the cylinder, a broken ring hanging in a port, bearing parts on top of a piston, etc., etc.

 

[New Boater Brad]

Re: 1985 75hp Mercury Wouldnt Start? Fly wheel would stick in same spot

Yes it is always a guessing game untill you tear into them.

Thank you very much for the information, I now have a few options to check out.

Ill perform the water check in the cylinder, then clean and rebuild carb's. I suspect they may be the problem, I have diffuclty priming at times. Even after changing tank and connectors at the tank.

If required Ill do a motor job, just dont know if it is fesible if it is a water leak into the cylinder.