1977 Mercury 850 cranks then stops

[JuJuOnDatBoat]

Just picked up a 1976 Steury x150 with a Mercury 850 and Mercontrol shifter...just changed out the engine wiring harness and spark plugs and followed procedure for starting and it cranks for a few seconds but right when it seems to fire up it stops cranking and starter just makes a continuous high pitch sound but isn't kicking over? Sorry this is my first boat restoration and got this far so any help appreciated!!

 

[Texasmark]

The whirring sound is your Bendix starting gear not locking in the teeth on the flywheel...usually caused by inadequate current in the starter to develop the thrust required to slam it into the gear...have your "fully charged" battery load checked at 300 amps and at least 10volts across the terminals at that time. If no, get new one. Then go to all your battery connections to the engine and clean up the terminals....take them off and clean internally.

Then tell us about your fuel and fuel components.....

 

[Chris1956]

Actually it sounds like the engine fired and kicked out the starter gear. The high pitch sound is the starter spinning freely. With the cowling off, it will be obvious.

Are you holding the choke button down while cranking? Need to hold it down on cold start, until she fires. Also, the cold start lever is full up?

 

[JuJuOnDatBoat]

Both were things I was thinking I am grabbing a new battery today and start there and yes on holding choke and never up thank you!

 

[Chris1956]

If she is firing and kicking out the starter gear, a new battery will not fix it. A tune up will fix it....