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Cannot turn my engine over by hand

english_man_in_norway

Contributing Member
"Mercruiser 4.3.Hi,im trying t

"Mercruiser 4.3.Hi,im trying to reset my timming after replacing ignition parts,ive tried a 16mm socket on the crank pulley,but it wont budge? Any advice?"
 
"You should be able to turn th

"You should be able to turn this motor with a normal size ratchet on the crankshaft. If you can't, you need to investigate further. Did the motor run prior to changing the ignition parts? What happens when you engage the starter?"
 
"Thanks for replying Rick,the

"Thanks for replying Rick,the story is 8weeks ago the engine overheated & stopped,the next morning it ran again,but didnt run it long,as i traced the problem to a stuck thermostat,i then went back to England for 6weeks & returned with a new thermo & ignition parts,the starter only clicked at 1st,but now cranks over & turns the rotor-arm,but won't turn by hand.Theres also rust on 2 spark plugs,any 'clearer' to you? Should I try getting the timming as 'close-as'& try running her for a while,then try turning by hand again?"
 
"I hope I'm wrong but it s

"I hope I'm wrong but it sounds like you blew a head gasket when you overheated it. Soak the cylinders good and get her to crank over OK, then do a compression test. If you can't get it freed up with a good soaking you're going to end up with the heads off anyway so might as well take them off now. Clean up the cylinders, replace the head gasket and pray the wrist pin didn't rust. There's no way of checking that without pulling it all the way down but you'll know soon enough. The rod will come through the block the first she sees 4000 rpms.

Good luck
Rick"
 
"Thanks for your interest Guy,

"Thanks for your interest Guy,its the 2 middle plugs opposite to each other,but there dosn't seem to be any sign of water in the oil?"
 
"Yeh Rick,I was secretly think

"Yeh Rick,I was secretly thinking it was the headgasket,the compression test was going to be my next 'ploy',I'm not up to 'full-speed' with boat mechanics yet,so how & what with do i soak the cylinders? Theres no visual sign of water in the oil,so I'l hope & pray this wrist pin is ok,as the thought of it coming through the block sounds very 'expensive'!
cheers Mike."
 
I think Rick has nailed it; ho

I think Rick has nailed it; hope it's only gaskets and not a cracked block.

Put a good squirt of PB Blaster or other penetrating oil in each cylinder; leave the plugs out when you crank it. Give it another shot of oil again.
 
"Thanks for your interest Rick

"Thanks for your interest Rick,you's all seem like a good bunch of guys on this site,I'l crank her over to get number 1 at T.D.C,hopefully then re-fit the ignition gear & see if I can get a compression test done,have you heard of this problem before where someones struggled to crank-over by hand?"
 
is there any reason why you ca

is there any reason why you can't crank the engine with the starter ? with the plugs out should be easy to get it back to TDC to put the distributor in.
 
"yeh Brian gona get the mrs to

"yeh Brian gona get the mrs to come down to the mariner tommorow to turn the ignition while i have my finger over number 1 plughole,just that I was working alone & usually I can turn her over by hand,but was frustrated that I couldn't."
 
"Update,'can't turn my

"Update,'can't turn my engine over by hand',thanks everyone so far for the help,got her turning over by hand now,but every now & then when turning I hear a distinct 'click',any idea's of what that could be? Also when ive finished cranking over for a short while & put my ear to the engine theres a 'ticking' like a clock or 'heart-beat' Is this normal & what is it?"
 
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