77 140hp Evinrude problems

[brokenspoke-1]

Hello. I have a 1977 140hp Evinrude model number 140743S. I'm having trouble with it when I get my boat up on top of the water. After I reach about 4500 rpm's the motor revs up like it kicks out of gear. I of course get oput of the throttle when it does that. I'm not sure what could be causing it. I've checked my shift cables & there doesn't seem to be anything wrong with them. It only does it after I get on top right before I start to trim the motor up. I was thinking that the dogs on the forward gear may be rounded but I'm thinking that it would do it when I'm coming out of the hole when there is the most load on the motor. Does anybody have any ideas?

 

[iwombat]

Re: 77 140hp Evinrude problems

From your description it could be a spun prop hub or cavitation, I can't tell.

Where is the anti-cav plate in relation to the keel? Does it feel like the motor is in neutral when this happens?

 

[brokenspoke-1]

Re: 77 140hp Evinrude problems

I immediatley get off the throttle & put it in nuetral when it happens. I never thought about the prop hub being an issue. I don't hear gears grinding like I think I would if it was the clutch dog grinding against the forward gear. What is the anti-cav plate?

 

[emdsapmgr]

Re: 77 140hp Evinrude problems

Follow Wombat's advice. If the engine is mounted too high on the transom, the prop will pierce the surface of the water and suck air into the blades, causing it to rev up. A spun prop hub will also cause cavitation-usually when the engine rpm's gets high in the torque range. Try another prop.