wmk0002
Well-known member
My wifes uncle recently bought a 2003 Mercury 25hp. It supposedly hit something with the prop and resulted in this twisted prop shaft. This isn't something Iv'e ever came across but told him I'd help him out. Seller already had it pulled so I was able to look at the drive and pinion gears and all looked good. I pulled the lower unit and the driveshaft was straight an seemingly undamaged as well.
I checked spark and it was very good. Then checked compression and was only seeing 70 psi on top cylinder and about 105 on the bottom.I decided to see if it would briefly fire up with some SeaFoam sprayed into the carb throat but it never even tried to fire. My assumption is that the flywheel key is probably sheared and it is way out of time but I haven't gotten to pull the flywheel yet. What are some other things I need to check that an impact that did this to the prop shaft may have caused? The compression numbers are concerning but hopefully it is a just a head gasket. I wish he would have checked those before buying...I would not have even purchased or would have negotiated the price down much further to offset the risk. Not my money though
I checked spark and it was very good. Then checked compression and was only seeing 70 psi on top cylinder and about 105 on the bottom.I decided to see if it would briefly fire up with some SeaFoam sprayed into the carb throat but it never even tried to fire. My assumption is that the flywheel key is probably sheared and it is way out of time but I haven't gotten to pull the flywheel yet. What are some other things I need to check that an impact that did this to the prop shaft may have caused? The compression numbers are concerning but hopefully it is a just a head gasket. I wish he would have checked those before buying...I would not have even purchased or would have negotiated the price down much further to offset the risk. Not my money though
![fMUL5Et.jpg](https://proxy.imagearchive.com/939/939bd147776020443ebcd1642dde241d.jpg)