What just happened?

[4327]

Hi Guys.
Here is an interesting one....
8 miles down the lake my engine quits.
(1986 140hp Mercruiser)
Running at about 1500-2000 rpm.
Just suddenly stops.
No extra noise.
Nothing.
I tried to restart but only get a "Clunk" from the starter.
Hook up 3 batteries....nothing.
At this point I am assuming the engine has seized.
I check the engine temp guage and it seems normal. (did it really cool down that quick in 10 minutes?)
Now did it really cool down that quick in 10 minutes? Maybe I missed the "Overheating" stage on the guage?
3 hours later (after rescue) the engine was still putting out heat when I removed the doghouse.
Back at home I get the same results when trying to start.
I decided to turn the engine by hand and it would not go forward.
I managed to turn the engine backwards about a quarter turn.
Turn the key.
Boat starts.
Temp normal.
Oil pressure normal.
Anyone know what happened here?

 

[Scott Danforth]

could be hydro-lock. pull your plugs and look for water. also check your oil

if it was just a click, that would be dirty connection, however a "Clunk" is the starter up against something solid....like a cylinder full of water

 

[4327]

Thanks Scott.
Oil is clear and no sense checking the plugs now as I have run it for at least half an hour.
I did have an issue with a plug wire 6 miles before this incident which I repaired on the water.
So what would happen if I was only running on 3 out of 4 cylinders?
Some type of vapor lock perhaps?

 

[Bondo]

I decided to turn the engine by hand and it would not go forward.
I managed to turn the engine backwards about a quarter turn.

Ayuh,....... Coulda been the Drive,.....

 

[kenny nunez]

2Xs on Bondo. Drain the oil from the drive to see what comes out.

 

[4327]

Interesting theory on the drive. Drained it and it came out clean.

 

[Maclin]

I would take a look at the spark plugs, see if any look steam cleaned compared to the others, or any have a bent electrode.

 

[4327]

I will check the plugs today Maclin.
Willreport back with my findings.

I have put a new impeller in the lower unit since I had it off anyways.
Now to get the lower unit back on....Any tips?
I tried yesterday but had some resistance so I packed it in for the night.
What I know so far....
- Drive shaft turns CW
-Turn shift shaft to right in order to obtain forward
-Shifter in forward when I took it off.
Seems like the resistance was coming from the shifter lining up with the copper tube.