1989 Mercruiser 3.0 carb rebuild

[johnnypac]

I'm at the end of a loooong transom rebuild project on a 89 Searay bowrider I bought 3 yrs ago which was said to be "water ready".... Engine all buttoned up, new gas, wires, plugs.... Still won't start... Hmmm... So I pull the carb and this is what I find... (Pics below)


So, since I've gained great insight from this forum over the last 3 yrs, I thought I might document my rebuild for the next poor soul who gets sold a carb like this....

Of course I have questions too.

First, any tips? I've rebuilt motorcycle carbs, never boat.

Second, what solution should I soak it in, and for how long?

Third, my rebuild kit does not have the spring that holds the filter/basket in place... Where the fuel first enters the carb from the gas line... I can't find it sold individually... Any recommendations?

Thank you guys for any help you might offer.

 

[achris]

Mercarb or Rochester? (1 idle mixture screw or 2?)

 

[johnnypac]

Mercarb

 

[achris]

Spring, Fuel strainer, part# 3302-9032. $2.25 at any Merc dealer or on-line shop....

When cleaning the carb, soak overnight in Carb-cleaner. Blow out with DRY compressed air. No real difference between a bike carb and a boat carb, just bigger, that's all...

Good luck...

 

[johnnypac]

Awesome, thanks for the part #.... And the advice.

 

[johnnypac]

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Made some progress today, got my rebuild kit in the mail so I tore it down.

Mercarb comes in 2 sections (Rochester, the throttle body separates making 3 pieces)
7 screws, one longer than the others... Keep track of where that one goes.

 

[johnnypac]

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This is the 2 sections divorced. Looking into the bottom... Float bowl and Venturi mech. The cylindrical hole on the right is where the accelerator assembly goes, the spring remains in that hole in this pic.

 

[johnnypac]

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Venturi cluster comes out with 3 screws. Gasket between the cluster and the body of the carb, remember to replace. Note that the enter screw is shorter and will require a fiber washer on re install. Also you can see a better shot if the accelerator pump assembly spring in the chamber.

 

[johnnypac]

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Power valve assembly coming out.... I didn't get a pic, but the main jets are just above. Remove main jets.

 

[johnnypac]

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Metal T comes out (this is just under the Venturi cluster) then a spring and then a stainless steel check ball. This was a booger to get out. Be patient.

 

[johnnypac]

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Next, on to the bowl cover assembly... The upper half.
I removed the accelerator assembly. some are straight, some are 90*. Mine is 90*
Note, after you remove the assembly, there is a small c clip holding the plunger to the bracket that must be removed to put on the new plunger.

 

[johnnypac]

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Next, I removed the float and needle and seat assembly. On reinstallation, there is a spring needle and a straight needle. From what I gather, spring is recommended but may cause stalling on hard L or R turns. Solid needle is used if you are having carb flood at idle. Pros and cons for both. Do some research before you decide.

 

[johnnypac]

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Lastly, the electric choke came off. Then the idle mix screw.... All metal parts are now sitting in Chem Dip carb cleaner over night. Reassembly tomorrow.

 

[searaytn]

Good stuff. I rebuilt my mercarb a few weeks ago. I have the same set of pictures and experiences. Couldn't agree more about the metal T being tough to get out. I ordered the kit from Mikes Carburetor and followed his videos. They are very good. Put the carburetor back on and boat cranked right up. Found other problems, but those are now fixed. However, put the boat in the water and runs great, but will not take full throttle. I can slowly accelerate and get up to speed, but if I give it the throttle it seems to be starving for fuel. I'm thinking I either screwed up the accelerator pump or did not set the float level correctly.

Good luck with the reassembly.

 

[achris]

... I can slowly accelerate and get up to speed, but if I give it the throttle it seems to be starving for fuel. I'm thinking I either screwed up the accelerator pump or did not set the float level correctly.....

Accel pump...

 

[johnnypac]

Yea, I've read those symptoms are consistent with something being wrong with the accelerator pump.... But what achris? I just want to make sure I get it right the first time.

And SEARAYTN, y didn't you do a write up on it? I searched on here and didn't find any, that's why I'm doin this one.... Although it's pretty straight forward, if there are others out there like me, I wana see it in pics before I do it.

 

[johnnypac]

ACHRIS, you mind giving me some insight on the spring needle vs solid needle? I'm thinking I'm going solid, just because that's what came out of it, and don't want to chance stalls on sharp turns. I'm open to some guidance/insight if you have any.

 

[achris]

Could be a faulty diaphragm, a check ball not seated properly, a spring missing. Without being the one who assembled it, it's difficult to say which, just look at everything associated with the accel pump circuit.

 

[johnnypac]

This is the vid SEARAYTN was referring to. Great info.

 

[johnnypac]

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