How to tell what carb I need?!?

[Timangas]

Recently bought a Baja 216DVS when I bought it the guy said the motor was replaced with a 350 mag the same year. Nothing the guy told us seem to be true though so I’m trying to figure out which card should be the right one on the boat. Right now it has a two barrel carb but only has 3500 RPMs at wide-open throttle with a 21 pitch prop. I have a buddy that says it should be a four barrel carb but there is a two barrel on there now. I looked at the serial number on the block and there is an option for a two barrel and a four barrel and it pulls up to be a 1988 350 mag. The serial number on the valve cover is worn off so I can’t see it. Is there anyway to tell what the crap carburetor should be for the motor?

 

[Fun Times]

Post the serial number there "might" be a way to know what came on it stock.

Also for most of iboats member in here, maybe try posting a photo of the engine intake manifold / & Carb to see if things looks normal/stock or not. A visual sometimes helps due to years of experience of just playing with boats.

 

[Timangas]

Post the serial number there "might" be a way to know what came on it stock.

Also for most of iboats member in here, maybe try posting a photo of the engine intake manifold / & Carb to see if things looks normal/stock or not. A visual sometimes helps due to years of experience of just playing with best pics I have at the moment I’ll post more tomorrow

 

[Chris1956]

4 bbl carbs require 4 bbl manifolds. Unless you are willing to replace the manifold, you will need to stick with a 2 bbl carb.

 

[Scott06]

I believe you are correct that the 350 mag should be a 4 bbl, but i think in yiur video it is showing a rochetser Quadra jet which is a 4 bbl. to be honest the video was not too useful as the camera was flopping all over the place . if you post just a close up of the carb and manifold it would help

I would verify the tach is accurate and i would go through the list of possible low WOT causes created in the stickies https://forums.iboats.com/threads/list-of-possible-causes-of-low-wot.289767/

you might want to ask a moderator to move this thread to the mercruiser as its in the mercury outboard section.

 

[Faztbullet]

That is a Quadajet 4 bbl and what up with the MSD ignition? Is it Marine or Automotive?

 

[achris]

Definitely a 4bbl carb on the engine in the video. And as it's likely a quadrajunk, I suggest you remove it and either send it to a carb specialist who knows those carbs (and tell him EXACTLY what it's from), or if you have experience with these carbs, strip and overhaul it yourself (not a job if you've never pulled a quadrjunk down before, or don't have the right tools to set it up properly).

Then we'll deal with that messed up ignition system. (I actually think the problem is most likely to be a timing curve or maximum timing issue).

Chris.......

 

[Lou C]

1) the Quadrajet is an excellent but complex carb, for marine use the small primaries and huge secondaries work very well.
2) these were last made in 1989 or so so they are all very old and you don’t even know if it was a marine or automotive unit (look for the yellow overflow tube between the pump and carb, that signifies it’s a marine unit).
3) I have an original non modified marine unit on mine and after reading articles and watching a few vids on the QJet I was able to rebuild mine in about 3 hrs including the cleaning. Ran 100% better after that.
4) There are a lot of resources here in the USA for Quadrajets, try Cliffs High Performance Quadrajets (forums and parts/rebuild kits) and Quadrajet Parts.com.
5) there are a few tricks to rebuilding these, just removing the air horn you have to figure out how to disconnect the choke linkage on the left side of the carb and drive back the roll pin on the left side to remove the accelerator pump linkage.
6) the cleaning, getting the air emulsion tubes clean is the main thing, I was able to get them clean enough for a good idle by soaking with carb cleaner and blasting them out with compressed air, an ultrasonic cleaner may do a better job, I might try that next time. I did not remove them as some do, I was concerned about damaging things then but it idled as well as it had after a shop did mine some years back, so that was good enough for me.
7) high quality rebuild kits are available from Cliffs as well as ethanol resistant accelerator pump units, the standard ones can be negatively affected by E-10 gas which is all most of us can use here in the USA unfortunately.

 

[Timangas]

I believe you are correct that the 350 mag should be a 4 bbl, but i think in yiur video it is showing a rochetser Quadra jet which is a 4 bbl. to be honest the video was not too useful as the camera was flopping all over the place . if you post just a close up of the carb and manifold it would help

I would verify the tach is accurate and i would go through the list of possible low WOT causes created in the stickies https://forums.iboats.com/threads/list-of-possible-causes-of-low-wot.289767/

you might want to ask a moderator to move this thread to the mercruiser as its in the mercury outboard section.

It’s a 2 bbl carb right now. But there are empty bolt holes on the manifold which makes me think someone put an adapter on there but I have no clue

 

[Timangas]

Here is what’s in there

 

[Timangas]

When I run the numbers on the block it comes back as a 1988 350 mag

 

[Timangas]

Also it came with an alpha drive if that matters

 

[achris]

Here is what’s in there

That is a 4bbl carb! Those extra hole are for a square bore mounting. The Q-jet is a spread bore, and doesn't line up with the extra holes.

 

[Timangas]

That is a 4bbl carb! Those extra hole are for a square bore mounting. The Q-jet is a spread bore, and doesn't line up with the extra holes.

Ok so you’d say that’s the original carb?

 

[achris]

Ok so you’d say that’s the original carb?

Yes, the 1988 350Mag was fitted with a Q-jet carb.

 

[Scott06]

It’s a 2 bbl carb right now. But there are empty bolt holes on the manifold which makes me think someone put an adapter on there but I have no clue

Who ever told you that is a 2 bbl is wrong. Thatis a 4 bbl Rochester Quadrajet. good news is properly rebuilt and set up it is a very good carb, dont get fooled by the quadrajunk, quadra bog or other comments you may see.
start with the basics check compression, look-at what comes out of the fuel filter, check ignition components and timing, especially total advance

 

[achris]

Standard troubleshooting for an engine.

Engines require certain things to operate properly... Basically they need the correct fuel/air mixture to be compressed and then fired at the right time.

So, in this order.

1. Compression tests.
2. Check spark plugs (and make sure they are the correct ones!), replace if needed.
3. If points, replace, along with condenser and rotor. Check and adjust, if needed, points cam dwell angle.
4. Inspect distributor cap, rotor and leads, replace if necessary.
5. Check spark quality (needs to be a nice BLUE spark drawn over 1/2").
6. Set timing. Check timing advance is working correctly.
7. Check/change fuel filters and check that the fuel system is not sucking air.
8. Check fuel pump pressure.
9. Check for full opening of the carb. Also ensure choke is opening fully when the engine is warm.

When all of these items have been done, THEN move to the fuel system....

You can have the best, cleanest carburettor in the world, but if the compression's low and/or the ignition system's not doing its job, the engine will still run like crap.....

Chris.........
25,000

 

[Scott06]

Also it came with an alpha drive if that matters

the fact that is an alpha doesn’t matter but you may want to verify the drive Ratio on the off chance someone swapped in a 1.32 ratio off a 454 powered boat.

 

[achris]

Determining drive ratio

Take the spark plugs out. Put the engine in forward gear. Have someone count the turns of the propeller as you turn and count the turns of the engine. When the prop has turned 10 times, divided the number of turns of the engine by 10.... That is the ratio.

For a 120 I would expect a drive with 1.98:1... So the engine will have to be turned 19.8 turns to make 10 turns of the prop....

Chris.........

 

[achris]

Post the serial number of the drive (Where is the drive serial number) and we can look it up. If the gear set is still original, then we can tell you the ratio.