Carburator from a 5.0 to a 5.7

[cptbraine40]

Boating Brothers and Sisters,

I am back to ask you fine folks about a carburetor from a 5.0 to 5.7. Here is the situation. I just bought a boat from a dealership that I have dealt with for a long while (so I know they are good). The gentleman that traded it had a Mercruiser 5.0 replaced about a year ago with the following:

Mercruiser Pro Series Roller Cam Long Block 5.7: Serial Number OF298867

When he did the switch, he used all the parts that are interchangeable from the 5.0 to the 5.7. and replaced the others parts with new parts (gasket exhaust manifold, intake gaskets, sparks plugs, cap and rotor, fuel pump, etc.)

I did an extensive boat test on the lake and the engine ran great (started with easy, obtained WOT RPM, idle smooth, etc.).

After getting to know my new boat, I noticed the boat has a Rochester 4 Barrel Carb (Serial Number 17080565 3114W). I looked up this carb and realize it was from his 5.0.

Is this carburetor ok for this boat? Should I look at replacing it with the proper one for this engine? If so, what is the proper carburetor for this boat? The reason why I am asking is because (1. I am sure the carb will need to be rebuilt in time since it has about 400 hours on it 2. Would like to have a new overall engine so I don’t have to worry 3. I have OCD and it will drive me crazy if this carb is the wrong one for this engine).
Thank you again for any assistance and information you can offer me.

 

[Bondo]

Is this carburetor ok for this boat?

Ayuh,... Over the years, that carb has fed everything from a 4.3l, to a 7.4l,... No Problem,....

Sounds like it's runnin' just Fine, 'n 400 hours is barely broke-in,.....

Enjoy it, til it tells ya, it's time for a rebuild,....

 

[cptbraine40]

Mr. Bondo sir, you are a gentleman and a scholar. Thank you so much sir. The boat does run great. That new long-block only has about 70 hours on it and it does run great. If you are not sitting down when you full throttle her, you are going to fly out the back . I just like to make sure my boat is in tip-top shape since Tennessee has a short boating season.

 

[Lou C]

The Rochester Quadrajet, if in good shape, is a very sophisticated carb and is adaptable to different displacement size engines As long as it runs well and performs well I would not change it. The Q-Jet was used on the 4.3, 5.0 and 5.7 engines, as well as the big blocks. However, it has not been used since the early to mid 90s if I recall, when the supply of new ones dried up. Mercruiser switched to the Weber (Edelbrock sells a version of this carb currently) and OMC/Volvo switched to the Holley. It is possible that the jetting and metering rods may be different for the 5.0 vs the 5.7, but if the engine runs well and the plugs read well when removed and checked for color, I would not worry about it.

 

[cptbraine40]

So Mr. Lou C, just to help increase my knowledge sir, when it is time to rebuild or replace this carb, will an Edelebrock work on this engine with the current configuration or will a need to get an adapter and other parts. Again, just curious sir.

 

[Bondo]

So Mr. Lou C, just to help increase my knowledge sir, when it is time to rebuild or replace this carb, will an Edelebrock work on this engine with the current configuration or will a need to get an adapter and other parts. Again, just curious sir.

Ayuh,.... The edelbrock 1409 will bolt on,....

The fuel feed pipe will need to be changed, 'n the throttle linkage,...

'n "Sir" was a name my Dad was sometimes called,....
Not so much myself,.... Bondo is what I've been known as for nearly 50 years now,....

 

[cptbraine40]

Yes sir. I am ex-Army and from the south..........ma'am and sir are always coming from my mouth sir. Again, I appreciate everyone' s input and information.

 

[kenny nunez]

When I had my shop I replaced many 305 s with a 350 and reused the Quadrajet with great results, I had a prop shaft dyno and I could not tell any difference between a stock 350 and the updated 305 to 350 reusing the original carbureator. I am sure there may be some difference but still cheaper than buying a new carbureator. I highly suggest that you stay with the Quadrajet, they are very good and rebuildable.

 

[cptbraine40]

Mr. Nunez, I am going to stick with the carb that is on it now and just enjoy it. Like everyone told me, it is the right carb and if it is running fine, leave it alone. . Your information is very interesting though and good to know. Any doubts that I had about having the wrong carb has melted away.....LOL

 

[Rick Stephens]

Capt Lou C (pronounced Lucy? ) posted what my first thought was, check plugs to make sure you aren't lean. After that, go boating. Sounds like you achieved a great upgrade going from a 5.0 to a 5.7. Happy boating.

Rick

 

[cptbraine40]

I am going to look at the plugs this weekend and make sure the motor is not running lean. Lets say for argument sake, they are brown (aka lean), what should I do next? Just change them out? I know, stupid question, but this how knowledge is obtained.

 

[Rick Stephens]

I am going to look at the plugs this weekend and make sure the motor is not running lean. Lets say for argument sake, they are brown (aka lean), what should I do next? Just change them out? I know, stupid question, but this how knowledge is obtained.

Brown is good. Lean is white. If too lean, then adjustments are required. Depends on where it is lean to what gets adjusted. Easiest of course is to open up the main jets, then power valve. After that it gets more complicated. If you see any lean condition on the plugs, take pictures of them and then run tests at various throttle settings, run for 5 minutes, then turn the engine off so the plugs are exactly indicative to that throttle setting. That tells us what might need adjusting.

You earlier asked the question of what carburetor to get should you ever decide to just swap out. I would agree with the Edelbrock 1409 suggestion. They are the easiest carburetor ever made to calibrate. Not saying you should do that. I did for my 4.3L, switched from Quadrajet to 1409, but the QJ was missing some parts.

 

[cptbraine40]

Also, just wondering, with the upgrade to the Mercruiser Pro Series Roller Cam Long Block 5.7, roller cams and lifters, 4 barrel carb, would you say the HP would be at about 260hp.............just curious since I have all you experts on here

 

[Bondo]

would you say the HP would be at about 260hp

Ayuh,..... That or Better,....

But it's only a number assigned, not a Dyno results,....

 

[cptbraine40]

Well Mr. Stephens, I am going to pull the plugs this weekend and take look. If anything is off, I will post some pictures and ask more questions of everyone . I am sure it will be fine, but hey, you never know. I would rather be safe and sorry. Again, thank you sir for your input, I greatly appreciate it.

 

[Rick Stephens]

Well Mr. Stephens, I am going to pull the plugs this weekend and take look. If anything is off, I will post some pictures and ask more questions of everyone . I am sure it will be fine, but hey, you never know. I would rather be safe and sorry. Again, thank you sir for your input, I greatly appreciate it.

I think your plugs are going to be just fine. Nothing like a hole burned in a piston top to teach minimal care when it comes to boat motor. Boat motors operate at 100% load. They are completely unforgiving of lean conditions.

 

[Scott Danforth]

Also, just wondering, with the upgrade to the Mercruiser Pro Series Roller Cam Long Block 5.7, roller cams and lifters, 4 barrel carb, would you say the HP would be at about 260hp.............just curious since I have all you experts on here

about 260 at the prop, about 300-310 at the crank

 

[cptbraine40]

Brown is good. Lean is white. If too lean, then adjustments are required. Depends on where it is lean to what gets adjusted. Easiest of course is to open up the main jets, then power valve. After that it gets more complicated. If you see any lean condition on the plugs, take pictures of them and then run tests at various throttle settings, run for 5 minutes, then turn the engine off so the plugs are exactly indicative to that throttle setting. That tells us what might need adjusting.

You earlier asked the question of what carburetor to get should you ever decide to just swap out. I would agree with the Edelbrock 1409 suggestion. They are the easiest carburetor ever made to calibrate. Not saying you should do that. I did for my 4.3L, switched from Quadrajet to 1409, but the QJ was missing some parts.

Pulled the plugs............they looked great. No concerns at all. Now, I just need some warm weather to go boating.........can you help a brother out? LOL

 

[Rick Stephens]

Yeah baby. Need weather. We've had a couple feet of snow over the last week. For here in Idaho, that is baseball weather. I'm a high school baseball coach. So normal start of our season. My boat's parked for another couple months.