Dead spot in throttle coming off plane

[BoatingCop]

I have a 94 Sea Ray Signature 220 with a MerCruiser 5.7. Ever since I e had the boat it will shift fine and accelerate fine. However when I back off the throttle to come off plane, I hit a dead spot in the throttle, which varies depending on what I was cruising at, where the RPM’s don’t change as I'm bringing the throttle back. Then all at once it will abruptly go to idle at which time the throttle works normally again and I can make fine throttle adjustments at low rpm. Has anyone experienced this? Could this mean the throttle preload needs adjusting, as has been suggested? Are there any good videos or write ups on this? Someone else has mentioned the throttle damper but I can't find much info on that. Thanks in advance!

 

[achris]

Sounds more like something in throttle control is binding. (Cable, remote control etc)... Remove the throttle cable from the carb and make sure the throttle moves smoothly through its fully range. If it does, start looking elsewhere... (Cable, controller etc)

Chris....

 

[harringtondav]

^^+1. If your carb is a Weber 4bbl, it has a throttle return spring located on the port side of the carb. One end of the spring is connected to the bottom of the throttle lever below the pivot. The other end is connected to the throttle bracket at the rear of the carb. It's a tight stretch.

With the throttle cable removed per Chris, the throttle lever and plates should slam shut when released from WOT. If the spring is missing, broken, weak or unattached it could be your problem.

While you have the cable disconnected check for excess play. With the controller locked in N, push and pull the cable end, and notice the effort required. If there is excess play, and the cable is sticky, it could explain the sudden drop in rpm when the spring suddenly stretches out the slack.

View attachment Throttle cable adjustment.pdf

 

[BoatingCop]

Thank yall so much and thank you for the diagrams!! I'll get to work on checking all of those things when I get the boat from where I'm storing it on Friday!

 

[TyeeMan]

I have this exact same irritating problem ever since I had bellows installed and an engine alignment two springs ago. Prior to that it was smooth as silk.
If memory serves the technician that did the work said he adjusted some cable something, something. I want to say he adjusted the shift cable.
I've lubed the throttle cable, checked the throttle return spring and still have this problem.