throttle problem with 700 Mercury Thunderbolt or Merc controls

[bhenry_2013]

I just got a boat with 70hp 1981 Mercury outboard with Merc controls on it. The motor starts great and runs and goes into gear. The problem is it won't throttle up. I am new with outboards. I see there are cables for fwd and rev. is the throttle/ timing advance controlled electrically? Just looking for a place to start and didnt really find anything in previously posted threads.

 

[carholme]

Re: throttle problem with 700 Mercury Thunderbolt or Merc controls

One of the cables is the shift and the other is throttle. Fwd and Rev are within approximately 15 degrees of Neutral and that is when the shifting action takes place. Depending on what model of remote box you have, you should see a little raised marker at the 15 degree points either side of Neutral, indicating Fwd/Rev. Beyond those markers is throttle cable movement.
When you have the cables disconnected from the engine end, the shift cable is the one which moves first.

Here is a link to the Merc Controls manual to show you the type of box you have.

merc controls newest manual - Download - 4shared

Click the Download button under View Document and when the next page opens, select Free Download

Gerry

 

[ajgraz]

Re: throttle problem with 700 Mercury Thunderbolt or Merc controls

Throttle and timing advance is purely mechanical on that motor.

Firstly, I'm gonna assume that by "won't throttle up" you mean it does not advance in rpm's AT ALL when you move the control lever. If it's something else (like bogging/poor power on throttle up) you must make that more clear.

Problem could be inside the box (e.g., bad cam), the control cable (e.g., cable broken inside sheathing), or the motor (e.g., carb linkages, any number of things).

Try to rule out a problem at the motor first. Put motor on muffs or a barrel, disconnect the throttle control cable at the motor, start 'er up, and see if you can rev it up (a little, don't go nuts!) by hand by moving the linkage the control cable attached to.