Mercruiser carburetor rebuild or replace?

[acdc96]

My 1986 mercruiser 260hp 350 V8 needs a carb rebuild. It has a Rochester Quadrajet 4BBL carb.
I've heard that the quadrajets are very complicated to rebuild.
So should i take on the rebuild or get a used Holley or edelbrock carb?
If I get a different carb which one do I get?

 

[Scott Danforth]

Re: Mercruiser carburetor rebuild or replace?

Q-jets are easy to rebuild if you have patience

The edelbrock is a Q-jet clone

 

[Capt Ken]

Re: Mercruiser carburetor rebuild or replace?

Rebuild for sure. They are pretty simple

 

[a1nowell]

Re: Mercruiser carburetor rebuild or replace?

acdc,
I am pretty good with my tools but carbs are beyond me. I sent my 2 barrel to these guys and they sent it back clean and adjusted, all I had to do is bolt it on.

Two Barrel Mercuiser Marine Carburetors

Larry

 

[Fishermark]

Re: Mercruiser carburetor rebuild or replace?

Q-jets are easy to rebuild if you have patience

The edelbrock is a Q-jet clone

The Edlebrock is a clone of the Carter / Weber - not the QJet. The Quadrajet is a spread bore, while the Edelbrock is a square bore. Rebuilding any carb is something that requires precision and patience - no cutting of corners. Even then it is sometimes a 50/50 proposition that it works right.

 

[Eric 3.7LX Alpha 1]

Re: Mercruiser carburetor rebuild or replace?

Here check this out.... series of videos for Quadrajet Rebuild by Alpheus, a member here.
http://forums.iboats.com/mercruiser...er-quadrajet-rebuild-video-update-362542.html

 

[jimbo_jwc]

Re: Mercruiser carburetor rebuild or replace?

Rebuilding hasn't been so bad as u usually have on a bench/table .Learned that cleaning and air doesn't always return to correct dia. on passages . What has got me a few times is the linkages as I forget after having off awhile so my standard is to take a pic before I start paint pen both ends a different color and shafts and use different colors on the others , springs also . I also will use wire markers on spark plug wires and distributor even though firing order is always visible . It has kept my rebuilding confidence up as I'm my worst challenge sometimes .

My 1986 mercruiser 260hp 350 V8 needs a carb rebuild. It has a Rochester Quadrajet 4BBL carb.
I've heard that the quadrajets are very complicated to rebuild.
So should i take on the rebuild or get a used Holley or edelbrock carb?
If I get a different carb which one do I get?

 

[achris]

Re: Mercruiser carburetor rebuild or replace?

Depends on WHY it needs 'rebuilding'... If it's just old and has a build up of dirty, it's not too difficult. If it's because parts are worn (like sloppy throttle shafts ect), then scrap it and buy an Edelbrock 1409 (Carter AFB/Weber clone). NEVER put a holley on a boat engine...

Chris............
(And I know I'm going to get a lot of crap for the last statement, but I stand by it. Merc stopped using holleys in the early 70s, for a reason!)

 

[jimbo_jwc]

Re: Mercruiser carburetor rebuild or replace?

Wait +++++ for it reason ? We got to know .

Depends on WHY it needs 'rebuilding'... If it's just old and has a build up of dirty, it's not too difficult. If it's because parts are worn (like sloppy throttle shafts ect), then scrap it and buy an Edelbrock 1409 (Carter AFB/Weber clone). NEVER put a holley on a boat engine...

Chris............
(And I know I'm going to get a lot of crap for the last statement, but I stand by it. Merc stopped using holleys in the early 70s, for a reason!)

 

[achris]

Re: Mercruiser carburetor rebuild or replace?

Wait +++++ for it reason ? We got to know .

Do you mean apart from the poor mid-range performance or as well as it?

 

[acdc96]

Re: Mercruiser carburetor rebuild or replace?

The engine has sat without running for 6-7 years (until recently when I woke it up from its slumber) and when I winterized 6 years ago I never added fuel stabilizer in the tank or flushed the fuel system. So I figure it needs a tune up. When I started the motor it was starving for fuel but ran decent. The motor would run decently at half throttle I've i put it in the neutral position it would stall immediately. If I advance the throttle it would rev up then die.
It's not a choke thing already solved that. And the engine was plenty warm.

 

[achris]

Re: Mercruiser carburetor rebuild or replace?

Yeah, sounds like the carb just needs a clean out. Strip it down, soak everything in carb cleaner for 24 hours (minimum), then blow all the passages out (with DRY compressed air, around 40-50 psi) and reassemble with all new gaskets. Check all the settings as you go. Do you have the Merc service-manual?

Chris.....

 

[NHGuy]

Re: Mercruiser carburetor rebuild or replace?

Get Cliff Ruggles Quadrajet book. It has tons of info, explains everything.
But give yourself some time. I thing I spent a couple of weeks after work and weekends doing it his way. I had to back track a couple of times to be sure I had it right.
Runs like fuel injection now though!
He explains what everything does and how it impacts each version of the carb.
If you are into aesthetics remove the choke plate and secondary plates before you dip. The carb cleaner will blotch the oe plating on them.
I think the most useful thing is that his book got me to remove the primary tubes so I could be sure the passages leading to them were perfectly clean. Most "normal" q-jet rebuild instructions don't mention that, and it's a place that crud could easily collect.
If you have any questions or trouble come back here and ask. We like to share what we have learned.

 

[NHGuy]

Re: Mercruiser carburetor rebuild or replace?

On the other hand since it runs well until it starts to not have enough fuel, just do the normal clean and gasket like Chris says.
That's less trouble and normally works.
If you have trouble later come on by and tell us how it behaves.

 

[Walt T]

Re: Mercruiser carburetor rebuild or replace?

Don't do it yourself if you've never done it. It's worth it to find some old bald fat grouchy guy (You know, Like me or Ken) who grew up rebuilding those in his sleep. Hey could be an old bald fat pms'n lady for all I know.

 

[acdc96]

Re: Mercruiser carburetor rebuild or replace?

Yep got the service manual from one of the forums and a clymer service manual(POS)
I'm gonna try to get in the boat today and get the carb out and work on it through the snow storm tomorrow. It's Covered with a layer of ice at the moment. (On the tarp)

 

[NHGuy]

Re: Mercruiser carburetor rebuild or replace?

Hey, I'm not that grouchy!

 

[Tail_Gunner]

Re: Mercruiser carburetor rebuild or replace?

To the op the fact you ask if it need's a rebuild is enough info to almost know with certainty you should have it rebuilt or buy a new one. A small simple 2 barrel can be tricky if it's not something you do on a regular basis. You need to know the routing circut's is the power valve working correctly and the linkage's binding did i get the float set up right and what float setting should i use for this carb..There ae a lot of variable's in a 4 barrel carb and even the seasoned pro's will tell you a rebuild is not a certainity even when assembled correctly..take care and good luck.

Hint: Violin wire works very well for cleaning some of those circut's.

 

[manley776]

I'm new to the boat world (at least the inboard boat world) after retiring from corporate crap and moving to a nice little lake in SW Michigan. Bought an '83 Formula Thunderbird with the 260 V8 that had sat for too long but fundamentals seem sound. Finally sorted out getting all the crap out of the fuel tank, replacing fuel pump (that died mechanically) went thru two tank check valves before I realized how much crud was in the tank and pumped it all out and flushed and cleaned etc. Boat is now running well but I figure a lot of crap has to be in the carb and given the age . . . there has to be problems. I'm a Brit car guy and can rebuild SU and Weber carbs but never much messed with American carbs. A couple of questions. The pickup pipe in the 25 gallon tank has no screen over the bottom end so any crud left in the tank will first find its way to a very small check valve coming out of the tank long before it gets to the fuel/water filter. Seems to me (after literally destroying a new one in the last go-around where the seat literally came out of its location and turned 90 degrees) that it should have a screen over its bottom end but the local guys who have worked on my boat don't seem to think that's an issue. while the boat now seems to run fine (I hate to tell you how many times I've been towed in) I distrust the carb. Normal running seems to create lots of fuel fumes. So what should I look for to determine if the carb is or is not rebuildable. Are there any off the shelf replacements? Are there reliable people to send the carb to for rebuild? Thanks. Otherwise love my gas-hog boat!

 

[Tail_Gunner]

A new carb is probably the way to go, trust me they have been improved and a carb as old as that is more than probably worn at every level.