3200 rpm or 4400.... no in between

[blazer7]

I just recently repowered my boat. Went from a 5.0 VP to a 5.7. Mechanic used many of the same parts from original motor to new motor ie pulleys, distributor, coil, starter etc.... Boat runs great except that when I'm running at about 3200 rpm and want to increase my speed a bit, I gently nudge the throttle.... nothing.... a little more nudge.... nothing and again, until suddenly the RPM's start to increase and run away. I try to back off a bit and now I'm back down to about 3200. It's even tough to keep it at 3200, it wants to slowly loose RPMs. I'm really at a loss here and my mechanic has lost all my faith in his abilities, but that's another story. The Carb was checked, no vacuum leaks, New cap and rotor, the throttle cable is smooth as silk when disconnected at both ends and pushed with one finger.... What would cause this?

HELP

 

[not enuf toys]

Re: 3200 rpm or 4400.... no in between

sounds like an issue with the carb - high speed jets, linkage, stuck choke

 

[blazer7]

Re: 3200 rpm or 4400.... no in between

thanks. I'm going out tomorrow and have my buddy actually watch the linkage and carb as I cruise around and make sure it's actually doing what it's suppose to before I start breaking things down. Simple things first. Thanks for the
input

 

[frantically relaxing]

Re: 3200 rpm or 4400.... no in between

What carb? Q-jet, Holley, Edlebrock--?

Sounds like a transition problem, and more than likely your engine is ready for more fuel but isn't getting it. When I put the Edlebrock on our Sun Runner (years ago) I played with the rods & springs to have the enrichment come in later (weaker rod spring) and with a little less fuel (smaller diameter lower rod)- My intention was to increase my fuel mileage, but what I got was almost the same problem you're describing. Got to a point where the throttle did nothing, and if I remember correctly it would actually start slowing down before I hit the vacuum point where the rod finally raised and dumped more fuel... then it wanted to speed up too much. I WAS able to run a leaner enrichment (but then our altitude is 4400' or more depending) but I found it ran better having enrichment coming in earlier rather than later. (after much testing, I found the 'out-of-the-box' setting was as good as it got!)

Could be your secondaries are opening too soon too, for whatever reason. This could cause a lean OR a rich condition, depending on circumstances.

Or...?

My bet is on a carb issue--

 

[dypcdiver]

Re: 3200 rpm or 4400.... no in between

I'd be checking the part numbers for the bits in the carb re. 5.0 and 5.7 to see if there are many differences and then get any different parts installed on your carb.

 

[blazer7]

Re: 3200 rpm or 4400.... no in between

Frantically...Thank you so much. BTW it's a Holley carb and I have a feeling my "mechanic" used some old parts on this carb to "save money". Pretty sure I'm not going to let him EVER touch my boat again. I do think I'm going to have someone else rebuild my carb though and see if this fixes any issues. Thanks for the input