Mariner 40HP Starting Problem!

[BillWint]

Motor was running but motor wasn't peeing! Two days later wouldn't spin fast enough to turnover (made sure motor was not in gear!). Pulled starter, hooked directly to 12vdc, starter spins fine. Reinstalled starter, motor spins, delays, spins, delays, etc. Bypassed cable from battery to motor with a brand new set of jumper cables - nothing changed. Hooked jumper cables to car battery (790 CCA) - nothing changed. Motor spins freely by hand. Removed spark plugs - motor spins freely. Reinstalled plugs - compression seems to keep motor from spinning fast enough to start. Plugs don't look great but can't believe these are the problem. I believe it is the starter but want to make sure - new starter is $350 - used is $115 (cheapest I have found). Want to be sure before I go making a substantial investment. ( I did take the starter apart and looked at the brushes - they looked fine to me!)
Where do I go from here?

[Walleye wonders]

I am having a similar problem with my Yamaha 75 hp tiller 2004. seems to be a on and off problem. once every 10 times I try to start the motor I get nothing? I have had the starter checked and it all tests out fine. but the solenoid could be the problem. I have found new 300 bucks at local dealer and 134 online from some joint in Georgia. I am going to buy the starter for 134 and start there. good luck

[99yam40]

Check compression to make sure all cylinders are sealing properly and are equal or close.

voltage drop test under a load should show any bad connections or cables.

Find a shop that deals with starters and alternators to have your starter checked out