wont throttle all the way

ok i have a 78 model mercury outbaord motor. we have had it worked on several times now this year it won't throttle all the way. when you get it about half way or more past the mid range throttle it will finally start to pick up speed. but anywhere before that it is just slow. could it be an ajustment that needs to be made or is something more?

Re: wont throttle all the way

You need to provide a little more detail on what's actually happening. All we know is you have a 1978 Mercury. Horsepower (model) and the boat it's mounted on might be of help don't you think? One one hand you say it won't throttle all the way. If you mean the engine seems to be running smooth but the throttle has to move too far before the motor responds that's one thing. If the engine is running poorly at anything less than half throttle that's quite another. If you mean you have to give the engine something over half throttle to get on plane that may be normal for your boat/engine combination. You can check the throttle action by removing the air box on the engine and observing the throttle plates (not the choke plates) as you open the throttle fully (with the engine off obviously). At wide open throttle the throttle plates should be perfectly parallel in the throttle bores. Give us something to go on! Slow is of no help whatsoever in your description.