Volvo Penta 454, w/ Holley carb issue

[larrymc]

I have a repowered 454 Gen V, starts and runs great for a little while, after longer trips the engine runs very fast and makes shifting imposible as the transimission locks up. This thing has been tuned by top mechanics and the problem persists, also added a new Thomson shift/controller, definitely engine/carb related. anyone seen this?

 

[Don S]

Re: Volvo Penta 454, w/ Holley carb issue

Got a full model number or serial number handy?

When it sticks at higher speed, can you manually push the carb linkage toward idle and get it to slow down?

 

[larrymc]

Re: Volvo Penta 454, w/ Holley carb issue

thanks Don. Doesnt appear to be a linkage issue, wont slow down if manually push this down. 7.4 Volvo with Mercruiser Bravo drive, cant find the serial #. original mechanic wont call me back, kinda' hosed. been this way since the engine was installed 3 yrs ago.

 

[Arabian180]

Re: Volvo Penta 454, w/ Holley carb issue

Check that the butterflies on the secondaries are closing.
I've seen these hang partially open and cause high idle. Pushing on the throttle cable will have no effect so you have to actually get a hold of the secondary throttle shaft and give it a twist. If that helps and the carb has never been apart it may just need a shot of cleaner & lube.

If the carb has been apart the secondary throttle plates may be off center causing them to hang partially open.