1976 MerCruiser 140 HP won't throttle

Joined
May 25, 2012
Messages
15
Thanks to this forum, we replaced a slave solenoid and got our 1976 MerCruiser 140 HP I/O running -- now turns over every time! No major injuries, fires or explosions for non-mechanics!

Our new problem is this: the engine keeps running in neutral and when put in gear. Prop spins slowly. No RPM change, no throttle. No strange noises or burning/melting smells.

The boat has been in a shed on a farm and not run since 2008, so some of the wiring has been attacked by packrats and/or decay after 36 years. We've been letting the old gas work out of the lines.

Any help is appreciated because this is the first time we've ever worked on a boat. We do have the original manual and wiring diagrams and can look up any additional diagrams we may need. Throttle cable? Carb trouble? Where to start?

Once we get this fixed, we're starting on the bilge and lights. Stay tuned.

You guys have been a great help -- thanks much in advance!:)
 
Joined
May 25, 2012
Messages
15
Re: 1976 MerCruiser 140 HP won't throttle

Ok after checking the cable that connect to the throttle this is what I found.

These 2 cables, marked by the green arrows, move.
Moving.jpg

Nothing in this area near the carburetor moves at all, marked by the red arrow.
Not Moving copy.jpg

What does that mean?
Thanks everyone!
 
Joined
May 25, 2012
Messages
15
Re: 1976 MerCruiser 140 HP won't throttle

Area with red arrow does move, but only when throttle is 85-100%. Is there a way to tighten it?
 
Joined
May 25, 2012
Messages
15
Re: 1976 MerCruiser 140 HP won't throttle

And the throttle is fixed! We think the area had gotten wet, and everything had gotten stiff. After letting WD-40 soak for a couple of areas, we reach full throttle forward and reverse fine. There is a "slack" area when going forward that it seems to accelerate more slowly, but it's definitely running full power now.
 

Ryanlewis2010

Petty Officer 1st Class
Joined
Oct 4, 2011
Messages
314
Re: 1976 MerCruiser 140 HP won't throttle

well if you can afford it i would suggest that you think about replacing them cause they will probaly freeze up again with in a short time not being used
 
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