Force 125 won't turn over

[KScott78]

Hello, I have a 1989 Force 125hp outboard. I used the boat 4 weeks ago for an entire weekend without issue. Now getting ready to leave for the long weekend and I can't get the motor to turn over properly. It turns very slowly, like the battery is almost dead, but the battery is full and I also tested with a backup battery I have here of the same make & voltage. Wiring is good. I even had an extra starter here and still the same issue. If I remove the spark plugs and turns the flywheel no problem. But not with any of the plugs in.

Any ideas what the issue could be would be a big help, I'm really at a loss here.

 

[Jiggz]

It could be the negative cable bolted to the engine block is loose or dirty. Don't just visually check it instead, unbolt it and clean it either with wire brush or sandpaper and also the other mating surface on the engine block. Bolt it back using a split lock washer and then try starting again.

If problem persists, jumper the starter solenoid (both large terminals using a screwdriver, hold on the insulated handle). If problem goes away you have a bad solenoid. If problem persists still, take compression test on all cylinders before going any further.

 

[jerryjerry05]

Like Jiggz suggested. Do a compression test.
If one piston's been damaged the motor can be hard to turn over.
If it's bad? you can really hurt the motor by running it.