Mercury 25XD motor won't turn

Joined
Apr 14, 2010
Messages
3
I've got a Mercury 25XD (not sure of year, I think 80's model) that quit on me yesterday. I hit a stump cruising along at about 10 mph. I examined the foot and prop and saw no damage. I cranked back up and headed in with no problems. When I got to the bank, it shut off. When I tried to crank back up, it seemed "locked up". I've looked at it today, and this is what it will do:

When I hit the starter, or pull the cord, the fly wheel will not budge.
In nuetral, I can move the flywheel backward about 1/4 turn.
In gear, I can turn the prop, which turns the motor and flywheel almost one full turn (backwards).
I took the sparkplugs out, and can see the pistons moving.
Put it back in neutral, and pull the cord, and the motor and flywheel will turn until it gets back to that spot, then stops.

Sorry for the lengthy post... just want to provide all the info.

Anyone know what might be the problem?
 

Barnacle_Bill

Admiral
Joined
Feb 8, 2004
Messages
6,469
Re: Mercury 25XD motor won't turn

Drop the lower unit and check again. This way you can tell if the problem is with the motor or the lower unit.
 
Joined
Apr 14, 2010
Messages
3
Re: Mercury 25XD motor won't turn

I dropped the lower unit. The motor still reacts the same. It's very weird. It has free play for a full turn of the flywheel, then it hits one spot and stops dead. I've never opened an outboard up, so I don't know what's going on in there.
 

jbjennings

Captain
Joined
Jul 18, 2007
Messages
3,903
Re: Mercury 25XD motor won't turn

I don 't have high speed internet so I couldn't watch the video. But it sounds like you could have sheared the flywheel key and the flywheel is wedging on the broken key piece when the magnet comes around. You might try taking off the flywheel and putting the flywheel nut on the crank and see if you can turn it then or at least see if the key is broken.
Just a guess,
JBJ
 

steve5959

Recruit
Joined
Apr 16, 2010
Messages
1
Re: Mercury 25XD motor won't turn

I have what appears to be a similar issue with my 2001 Mercury 25hp. The engine was running perfect last fall prior to being winterized. I've spent the better part of an afternoon trying to figure out why the flywheel locks up, with no solutions yet! The video that you posted could have been taken by me on my 25 merc. I'm not a boat mechanic, but I'll keep you posted on any fixes that I come up with or if I find any other forum on merc's that addresses this problem.
 

will941s

Chief Petty Officer
Joined
Oct 1, 2007
Messages
540
Re: Mercury 25XD motor won't turn

I was looking at the video on Youtube and I heard a metallic clunk sound when it stopped. Sounds like it was coming from inside your block. Could be possible that something snapped inside the motor and is wedging the crankshaft against the block. Maybe a part of the connecting rod or something from the crankshaft. If it was a dead stop something probably just "gave" inside the motor. If both pistons are still moving it is possible that one of them is just barley holding onto the crank shaft. Might have to open it up to see what happened. Keep up posted on the outcome.
 

sschefer

Rear Admiral
Joined
Nov 13, 2008
Messages
4,530
Re: Mercury 25XD motor won't turn

I was looking at the video on Youtube and I heard a metallic clunk sound when it stopped. Sounds like it was coming from inside your block. Could be possible that something snapped inside the motor and is wedging the crankshaft against the block. Maybe a part of the connecting rod or something from the crankshaft. If it was a dead stop something probably just "gave" inside the motor. If both pistons are still moving it is possible that one of them is just barley holding onto the crank shaft. Might have to open it up to see what happened. Keep up posted on the outcome.

I was thinking the same thing. I wonder if a rod bolt broke and the head of the bolt fell out when the engine stopped.

Pull the flywheel off and drop the lower unit. If it still locks up then it's inside and you'll need to tear into it.
 

will941s

Chief Petty Officer
Joined
Oct 1, 2007
Messages
540
Re: Mercury 25XD motor won't turn

I'm thinking that or a bent connecting rod....one or the other. Remove the powerhead, pull the flywheel and electronics, and crack her in half. You have to remove the carb and the intake plate/reeds to get to the bolts inside the block. Hopefully with the low RPM's whatever "gave" did'nt damage anything else. Let us know what happens.
 
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