115 Johnson slow cranking

I just bought a boat with a 115 johnson and when I treid to get it running it was cranking very slow on a fresh battery. I bought a new starter only to find the same exact problem. It almost seems like the motor hads to much compression. When I take the plugs out it cranks fine. Can anyone tell me what they think might be going on. Thanks

Re: 115 Johnson slow cranking

Check to insure that the large cables coming to and from the starter solenoid are clean and tight.Also insure that the ground lugs to engine block are clean and tight as well.If that all checks out you can try jumping the solenoid with a good high tension lead and determine whether the solenoid contacts could be culprit.

Re: 115 Johnson slow cranking

90% of starter problems are bad connections. remove and clean both ends of the battery cables, so that they are shiney, also the cable from the solenoid to starter. check for nicks in the cables. and make sure the connectors are on the wire good. the cable tend to corrode from the inside out, if nicked, corroded wires, and connections, heat up and cause resistance to the follow of electricity, thus the starter doesn't get enough. you can also take jumper cable pos battery post to large post on starter. with a good connection, the engine should spin. then if the starter is good clean everything and retest. then trouble shoot solenoid. starters can be rebuit at a starter/alternator shop, much cheaper than a new one.

also have the battery load tested at the auto parts store, free, i've had new batteries go bad

Re: 115 Johnson slow cranking

Thanks guys for the advise. I have had the battery tested and its good. I also eliminated any ground problems I think by going directly from the positeve side of the battery to the positive post on the starter and from the ground on the battery direcly to the engine block. Nothein but hot jumper cables. Is there any way that there could be a problem with the exhaust pressure not being able to escape the engine?