Mercury 80 won't crank with plugs installed

[essdee]

Twin Mercury 80 HP 4STK (2007) not turned over in 2 months. Hot climate and stored under shade. Port engine fires up immediately. Starboard engine does not crank. Starter engages but cannot turn flywheel.

Attempted to manually turn flywheel but very stiff. Removed all 4 spark plugs and manually turned flywheel. Lots of gasoline vented from lower two cylinders. Initially flywheel was stiff, but then was able to make several smooth complete rotations. Additional gasoline vented from lower cylinders as the flywheel was manually turned. I do not know if this is normal but seemed excessive.

Cleaned up gasoline and made safe. Re-installed and torqued spark plugs and pencil coils. Tried starting but issue not resolved. Tried to manually turn flywheel, but was again stiff and would not move past a certain point.

Since flywheel turns smoothly with the spark plugs removed, the issue seems to not be a jammed impeller or seized piston rings. Any thoughts or guesses before getting the workshop involved? Thanks in advance!

 

[jimmbo]

Bent/Twisted Connecting Rod, if the Motor Hydrolocked when cranking

 

[essdee]

Bent/Twisted Connecting Rod, if the Motor Hydrolocked when cranking

Thank you very much for the quick reply.

Motor last started in shed with muffs in Jan/Feb and run idle for 10 mins to keep things operational. Boat has not been in the sea since.

Assuming issue is hydrolock (and potentially bent rod), why would removing spark plugs from cylinders allow flywheel to be manually turned? I can also see the pistons rising and falling through the spark plugs holes. A bent rod or hydrolocked engine would not allow flywheel rotation, if understand this correctly.

Sorry for the questions, I am just trying to understand the mechanics involved.

 

[jimmbo]

Removing the Plugs, allowed the Liquid to drain, removing the cause of the Hydrolock. A very slightly bent/twisted Rod, can cause Binding/Tight spots, but still allow rotation, even complete rotation of the Crankshaft.

 

[essdee]

Removing the Plugs, allowed the Liquid to drain, removing the cause of the Hydrolock. A very slightly bent/twisted Rod, can cause Binding/Tight spots, but still allow rotation, even complete rotation of the Crankshaft.

Thank you. I will call the Mercury service centre.

 

[airshot]

Bottom line is....there should not be liquid in the cylinders like that...you have a problem but I can't say what it might be. Better to get it looked at by someone that knows.