120 hp Merc + outdrive tuning

[p3ghost]

Howdy all. I am looking for any help with tuning up the motor to outdrive functions. I just rebuilt a 120 hp motor and dropped it back in the boat yesterday. Got it running well, but I know there is still lots of work to do. Basically, it shifts well into forward and reverse and increases rpm as it should....but as I pull the throttle back to neutral....the rpm stays at the highest level achieved and won't reduce unless I turn the motor off and restarted.

I searched the forums, but having a hard time finding it referenced somewhere. Any help or links would be outstanding!

Thanks

 

[Bondo]

Re: 120 hp Merc + outdrive tuning

Howdy all. I am looking for any help with tuning up the motor to outdrive functions. I just rebuilt a 120 hp motor and dropped it back in the boat yesterday. Got it running well, but I know there is still lots of work to do. Basically, it shifts well into forward and reverse and increases rpm as it should....but as I pull the throttle back to neutral....the rpm stays at the highest level achieved and won't reduce unless I turn the motor off and restarted.

I searched the forums, but having a hard time finding it referenced somewhere. Any help or links would be outstanding!

Thanks

Ayuh,.... Welcome Aboard,.... Did ya align the motor to the gimbel when ya put the motor in,..??

What's the vintage of this stuff,..?? gotta know to see which manual...

Sounds like a broken throttle cable...

 

[p3ghost]

Re: 120 hp Merc + outdrive tuning

It's a '78 Starcraft that originally had a mercruiser 140 i/o. The block was cracked so I rebuilt it as a 120 hp. Outdrive is...I think...an Alpha 1. Everything matched up well when I put the motor in, and I made sure the outdrive was in forward gear before aligning and reinstalling.

Same thing happens when I use the "RPM only" lever on the side of the console.

 

[p3ghost]

Re: 120 hp Merc + outdrive tuning

After doing some tinkering...I think it just might be a sticky throttle cable. I shifted into forward gear and advanced the throttle to increase rpm...then I pulled it back into neutral and walked back to the carb and manually reduced the rpm by pulling the throttle cable back.

Sound reasonable?

 

[Bondo]

Re: 120 hp Merc + outdrive tuning

After doing some tinkering...I think it just might be a sticky throttle cable. I shifted into forward gear and advanced the throttle to increase rpm...then I pulled it back into neutral and walked back to the carb and manually reduced the rpm by pulling the throttle cable back.

Sound reasonable?

Ayuh,.... adjust the throttle cable at the carb...

The cable should be puttin' a Slight pressure against the idle stop screw....

 

[p3ghost]

Re: 120 hp Merc + outdrive tuning

You were spot on! I adjusted the idle stop screw so it was holding pressure on the linkage, and now everything is working great! You are officially my hero.