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Which carburetor?

M

Mike29

Contributing Member
I was wondering if anyone has a favorite carburetor they like on the Crusader 454/350 H.P. Thermo Electron motors. I currently have the Rochester Quadrajets that I rebuilt with Cliffs kits and they run great but there are guys in my marina with heavy boats that say they get a couple tenths better with the Edelbrock carbs. This would put me in the 1 mile to a gallon club if true LoL. Any thoughts?
 
I have Q-Jets on a pair of 454XLs and like them just fine. Before going thru the expense of new carbs might research fine tuning your current carbs. Suspect factory settings are a compromise to work in all applications. Experts could probably recommend different metering rods, secondaries tip in scheduling, and other adjustments which might optimize your performance. Step one would probably be installing the instrumentation to measure performance. Don't see too much on 454 fuel economy. If you take on the challenge please share your experience in crashing the 1 mpg barrier.
 
Mullet's suspicion is Spot On - the factory delivers the engine with a carb on top that doesn't come with options....and they have NO IDEA what kind of hull it is going into (let alone what gear is getting bolted to it). And it has to "work well" to get them thru the warranty period.... This means most every marine carb is tuned rich and if you can minimize that, the fuel economy will improve proportionately...

You also need to have realistic expectations - a 30,000 lb hull trying to do 30 knots will consume enough fuel to make the owner take up a new hobby..
 
I kept the quadrajet on the 454/model 350 Crusader engine we rebuilt over last winter. Everything seems fine but it does seem to idle a little rich. I researched the idle mixture screws and the adjustment procedure looks easy enough, but where do I find that special tool for those screwheads? They are a protruding rectangular shape with rounded corners. I'd hate to have to paw away at them with a pair of pliers!
 
They need what're called a double d socket...you can buy them off the internet or at a good parts store...I've found just the long (1.5") version works well with my fingers but I have small hands). you can also get a small piece of copper tube and mash the 'flats' into it..there's not much friction so it works ok...
 
makomark said:
They need what're called a double d socket...you can buy them off the internet or at a good parts store...I've found just the long (1.5") version works well with my fingers but I have small hands). you can also get a small piece of copper tube and mash the 'flats' into it..there's not much friction so it works ok...
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Thanks Mark!
 
Jeff...if my 13000 pound boat got 1.2 at 20 I'd be happy. My boat gets .7-.8 on cruise. It is a Blackfin with the really deep vee. I was asking because a fellow at my marina switched to Edelbrocks on his BB mercs and swore his mileage jumped .2-.3. But he did admit his old carbs needed an overhaul. My boat cruises best at 3200-3300 but I know I'm in the secondarie side of the q-jet.. I've tried keeping her down to 2900-3200 but the boat just seems to push water and burns more fuel untill I hit 3200...3300 where she is planed out nice and singing. (EDIT)... Cliff Ruggles finally answered my post on his site and said the secondaries on my boat can be tuned to be more efficient so maybe I'll go down that road first. I need his book. He has the idle mixture scews that are slotted for a flat blade screwdriver also for you guys needing them for your marine carbs. I did this mod when I overhauled my Q-Jets..makes idle adjustment much easier.
 
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Yikes! How you got Exxon stock!

You might try locking the secondaries closed (with some wire, so they can't open). I hear that improves gas mileage. Getting on plane will be a bit slower, however.

Jeff
 
He'd be better off tune the carb for the application as Cliff suggested....you really can't shut off the secondaries on a q-jet but you can impede their function by ty wrapping the air valve....there are MANY different adjustments that can be made to those carbs so you have to be methodical and patient. You also want to make sure the engine is tuned well before you begin.

Doug Roe's book is also an excellent reference for some of the tuning nuances available....
 
Thanks for the advice guys...excellent as ussual. Just wanted to be sure I'm thinking straight before heading down that trail.
 
Anybody know if a CFI conversion would yield a significant performance improvement ? Not a fan of FI on boats since reliability is impacted by the environment. I have been towed home enough to appreciate carbs and points ! Just wondering if the conversion would ever pay for itself.

FL Panhandle
 
Probably not. Run at a constant speed--and tuned correctly--a carb is nearly as efficient as EFI. It's that city driving cycle that makes EFI autos so effective.

Jeff
 
Unless you can find a "conversion package" really cheap and you use the boat a whole lot (600+ hrs/yr) it is NOT cost effective...like Jeff said, if its tuned correctly, the carb can deliver 14:1 a/f ratio just like a set of injectors can...its the RPM transitions where their efficiency suffers.
 
Hi Mulletwagon! You know me as machmike on our blackfin site. I agree with Jeff and Mark. I had a discussion with another member on our site about fuel injection versus my carbureted boat awhile back. His F.I. xl engine doesn't do any better than my boat with the carbs. Look at the money Blackdog spent on those horizon 8.1's for not much higher cruise and same fuel burn as me. I'm convinced when the time comes if I cant go Cummins or Yanmar power to just overhaul my 454's and be done with it. Mine are running great right now so hopefully thats further down the road but we are always looking for better efficiency.
 
Mike29 said:
Hi Mulletwagon! You know me as machmike on our blackfin site. I agree with Jeff and Mark. I had a discussion with another member on our site about fuel injection versus my carbureted boat awhile back. His F.I. xl engine doesn't do any better than my boat with the carbs. Look at the money Blackdog spent on those horizon 8.1's for not much higher cruise and same fuel burn as me. I'm convinced when the time comes if I cant go Cummins or Yanmar power to just overhaul my 454's and be done with it. Mine are running great right now so hopefully thats further down the road but we are always looking for better efficiency.
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Hey Mike - I always read your posts. Seems FI is really not optimal for large boat applications. Simplicity usually means reliability which is more important than performance. For me the best compromise is electronic ignition and carbs. Just my $.02.
 
Totally agree.

If a carb screws up ten miles offshore one can often fix it with simple tools, but if an EFI set up dies...

Jeff
 
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