1987 Evinrude 40 HP cranking slowly

[Rapid Robert]

I have a 1987 Evinrude 40HP 2 cycle motor that is giving me cranking problems. It will barely turn over.
When I bought the boat/motor 4 months ago, it turned over with no problem. I have read all the comments on this site about checking the cables & battery and all connections. I have done all of those. I have disconnected all the wires to the starter and connected the battery directly to the starter. Same result?slow turn over. I just came back from a starter repair shop and they checked out the starter and said nothing was wrong with it.
It turns over fine with the plugs out. I?ve sprayed WD40 in the plug holes and turned it over several times and still slow turn over with plugs in.
The only thing I have done to the motor since I bought it was lubricate several points per manual and change the lower case oil. I also hooked up the garden hose to the thong adapter when I first tried to start it.
The only things I can think of it being is either the batteries (I also used my car battery to jump it) don?t put out enough cranking amps or there is something causing excessive compression. Any ideas out there, guys???
Also if I buy a new battery, what size should I buy?

 

[tashasdaddy]

Re: 1987 Evinrude 40 HP cranking slowly

battery cables are the # 1 problem, the get a nick, corrode inside, causing resistance, and the starter not getting enough amps. i have seen cables that only have 2 or 3 strands of wire still connected, and it would turn the starter. it is a good way to burn up a starter.

 

[Rapid Robert]

Re: 1987 Evinrude 40 HP cranking slowly

Thank you for your reply, tashasdaddy.

I took the cables out of the equation by disconnecting the cables from the battery to the starter. I used jumper cables to connect directly to the starter and same result...slow turn over.

Oh oh, I just thought of one thing. I haven't checked the ground connection on the starter motor. That could do it, right?