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1993 40hp Mercury problem (with video)

G

Greg Pasq

New member
Hi All,

We have this engine on our pontoon. In the video, I am not increasing speed at all. Around the 12 second mark you'll hear the engine start to rev and the only way to stop it is to reduce speed. Any ideas what could be causing this? I appreciate any info!

VIDEO: [video]https://1drv.ms/v/s!AshkKYMzB-VRgYAW-ofzr8atqSPeOg[/video]

Greg
 
Slipping hub or ventilating (sucking air) do you have pics of the back of the boat with the motor down out of the water? My guess is the prop starts sucking air when the boat gets up on a plane. Maybe build a jack plate to lower the motor down a few inches?
 
Thanks for the replies. After I posted this, the water pump stopped working so I had to take it out of the water. Hoping to take apart the engine tonight.
 
I had my hub slip the first day i went out on water after buying a standing boat.. I opted to buy a new prop since the process of pressing out those hubs on old corroded props was a gamble at the least, so i drilled and tapped 3 holes and pinned it (permanently fixed) and keep it on the boat as a spare. On a one engine boat always good to have a spare prop, esp at sea. Fyi it worked fine - only caveat is if u hit something hard and solid u can damage gearbox..

anyway - just thought id throw that in there, yes revs picking up is def a sign of a hub starting to slip - it will get so bad u wont make it past 1800rpms..

fyi i used 1/4mm stud inserts with the hex inside - so u can basically keeps crewing it thru the hole, ie no head.. just a threaded thing with a hex hole on one side to screw it in by -
 
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