100hp 1979 100999s outboard wont cycle

it cranks up but wont start , wont cycle.i check and change spark-plugs, the new ones got wet so im assuming fuel gets to them but doesnt make combustion, it overheated it couple time the engine, i have issues when i start the motor, i have to push the choke towards the back crank it couple times till it runs, then will day , i pull the choke forward and it will start with the idle all the way up!!! then if i wanna go forward i have to slam the throttle all the way forward so wont kill the motor!!! last time i used it i had to go trough all this and while going back to the marina it stopped , i repeated the moves , it started then died again after 200 yards , did that one more time then it didnt start anymore had to paddle to the shore!!! now it wont start at all !! any if u can make any sense from what i am saying pls help!!!

Re: 100hp 1979 100999s outboard wont cycle

Check the compression on each cylinder with a compression tester. They should be over 100 psi and close to one another.
Check the spark at each plug with a spark tester. It should jump a 7/16" gap.

Re: 100hp 1979 100999s outboard wont cycle

This is what I'd do: check compression on all cylinders, since you've overheated the motor a couple of times, chances are good you may have a bad head gasket (hopefully that's all), next, do a spark test and affirm all cylinders are getting consistant spark, then I'd do a carb cleaning/re-build on each carb. After all that, I'd suggest pulling the lower unit and replacing the impeller. It wouldn't hurt to replace the thermo stat while you're at it. Not terribly expensive if you do the work yourself.

Re: 100hp 1979 100999s outboard wont cycle

Sorry TX, you must type faster than I do!