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Need some help with 25hp mercury outboard

9

96pursuit6.2

New member
Okay so I bought a 2000 mercury 25 outboard that hadn't been used for awhile. It was in great cosmetic shape and starts and runs fine until almost wide open throttle. At that point it will shut down and I can't pull the rope. It's seized somewhere at that point. After sitting for awhile it starts and idles fine. There is no scouring in the cylinders and the compression is at 120 on both cylinders so I'm led to believe the issue is not there. It has done this repeatedly. The thing is cooling great as well. Steady stream and max cylinder temp is 138. I'm lost here. The thing runs super strong until wide open. Also, when it does stop there is a light clicking sound until I return the tiller to neutral. I have had it at the shop with no luck other than a possible crank bearing seizing when it gets hot? They were baffled. I'm hoping somebody has seen this before and can provide any insight. The serial number is OTO43459.
 
The clicking is normal just the prop turning when the motor shuts down. Drain the lower unit and see if you get metal out.
 
Yeah I didn't think about the clicking sound enough. Definitely what that is. I drained the lower last night and the fluid looked great. No metal and no water. Ran it again last night in the driveway and she is purring. Took some temp readings all over the powerhead to see if anything stood out. Areas around the bearings were right at 100 degrees. Cylinder temps were 128 top 108 bottom. I would rather not take it back out unless I find something.
 
First verify that the oil injection is working/OK. Can it run at say 3/4 throttle for a lengthy time ? IF so re check the temps? When it seizes did you re check the temp readings ?? Did the plugs look to be running too hot?
 
Canufixit said:
First verify that the oil injection is working/OK. Can it run at say 3/4 throttle for a lengthy time ? IF so re check the temps? When it seizes did you re check the temp readings ?? Did the plugs look to be running too hot?
Click to expand...

What oil injection! If that motor overheated highly doubtful it would run again Mercosil blocks do not handle overheating!
 
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