72 Johnson starting problems

[qboatingnovice]

I am new to iboats and not much of a mechanic, but I'm sure that someone will be able to pinpoint my problem. I have a 72 Johnson 100 hp that is turning over very slowly (100ESL72R). Flywheel turns over by hand but has "hard spots" with plugs in, yet turns over smooth by hand with spark plugs pulled out. I bought a used starter a couple of days ago and Im waiting for the rain to let up to install it. Why would it

 

[Bosunsmate]

Hard spots is normal , its the compression. try jumping with jumper cables straight to starter.
It might be corroded wires or bad used starter or burnt up solenoid

 

[qboatingnovice]

I tried that but the starter still slowly turned the motor over...bought a used starter and hoping that's the problem.

 

[emdsapmgr]

It may not be a problem with the starter. To test it, run a set of automotive jumper cables to it from a known strong battery-direct. If it cranks normal rpm's when jumped, the starter is ok. Then have a look at the solenoid, as was mentioned by Bosunsmate

 

[F_R]

Nobody has suggested the most likely thing. Have the battery load tested. It may have a dead cell.

 

[boobie]

Are the battery cable connections clean and tight on both the battery and the motor. ??