Mercruiser 5.7 troubles. Pulling what hair I have left out

[proshadetree]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

Yes They are mostly external Pump and secondaries are outside

 

[jy118lfd]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

Thaks for the ideas. I will have to buy that book. I have never been afraid to tear apart a engine, but carbs scare the hell outta me. I have no idea why. I have always heard the Qjet is a great carb, if tuned right. My boat is trailered, and I worry that it will be a process of unload the boat, try it out, reload, tear apart tune, unload boat, try again. If I rebuild this carb to specs of Cliff, will my tuning be able to be done in the water, and not tear apart the carb?

Abosolutly, I have not had to take my carb off since. I did use a smaller primary jet as he recommended 74 jets and I settled on 72s because it was a tad too rich and a little sluggish. But the jets are easy to change. When you go though the book you will see how to do everything and it is a piece of cake. Nothing to be scared of. All your friends will think you are god because you figured out a quadrajet.

 

[christoner2002]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

Got the boat fired up last night. I tried to set the timing on it. If I set it to the 8btdc it says idling,(600rpm) the engine does not want to stay running, and pops, when giving quick throttle up. If I set it to 11, it seems to run great. This is not under load(not water tested). Also, It says it has the Thunderbolt V ignition system, which says to ground the purple/white wire to get into service mode to set timing. In the book, it says Thunderbolt V should have a knock control module on it. Mine does not. But it says Thunderbolt V on the carb cover. If I connect the purple/white to ground on Battery, it does not put it in service mode. Even grounded, if you bring up RPM's, it advances. Am I doing something wrong? Please help.

 

[John_S]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

A number of engines have T5 with no knock module. Attach the purple/white wire before starting the engine. Set timing to 10 degrees BTDC. Adjust idle mixture, adjust idle speed to 650rpms, repeat idle mixture / speed for a few iterations. Shut off engine. Remove ground.

 

[christoner2002]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

Well, I made good and sure the purple/white wire was grounded today, started the boat. Went to set the timing, and if you bring up RPM, it still advances on me. I cannot get this turd to run at 10BTDC even. It wants 12BTDC. The mixture screws on the carb are not a typical screwdriver. I don't have a screwdriver to adjust them. I did the compression test again, and every cylinder is now good. When in my driveway, on the hose, it runs ok, at idle. If you really wrap the throttle quick, it pops out the carb.

 

[John_S]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

Well, I made good and sure the purple/white wire was grounded today, started the boat. Went to set the timing, and if you bring up RPM, it still advances on me. I cannot get this turd to run at 10BTDC even. It wants 12BTDC. The mixture screws on the carb are not a typical screwdriver. I don't have a screwdriver to adjust them. I did the compression test again, and every cylinder is now good. When in my driveway, on the hose, it runs ok, at idle. If you really wrap the throttle quick, it pops out the carb.

For the q-jet mixture screws, get one of those flexible shaft (with attachment) from the auto store.

I5 had the idle mixture screws turned all the way in on mine. It will not run well at 10 like that, and if you checked vacuum it would be on the low side. It would run better at at a higher 12-14 BTDC.

While I know that it has been stated here that base mode locks the ICM, that has not been my experience with 3 different module on my boat (including new retrofit kit). Base mode clearly removes the auto idle adjust, and I believe the other T5 adaptive functions, and leaves just the base timing curve.

I'd wager that once you get your mixture screws adjusted you will be able to time it.

 

[christoner2002]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

I will have to buy that tool. Water test went pretty good all in all. The boat deffinately has more balls to it. The bog is still there, but not as noticable. I put a matched set of metering rods a buddy had laying around. Not sure if they are right. I5 is sending me the right ones(or so they say). It runs great at top end, but if you back of the throttle just a touch, it pops a little and spits and sputters, right when the secondaries are closing it seems like. It seems like a mid range lean condition. I will reset the idle screws and give this carb one more try with the "correct" metering rods. Hopefully that will correct it. Anyone know what the correct metering rods should be for a 350?
Also, I will order Cliff's book on Qjet's. Thanks to everyone for your help. It really is nice to have a great group to run ideas and questions by!

 

[John_S]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

You will probably need the book to help out on the jetting. It depends on the qjet model. If you got one that is an exact match to the marine, those jets/rods are known. I5 sells car carbs that have been modified to marine. Sometimes they are a different type, and don't use the same rods as others. Metering is different, and will need to adjust based on testing. The one I have is different than typical Merc. If you have the electric choke version they sell, it is probably the same as mine.


Merc varied some between engine models, but this is a common calibration:

Primary jets: 0.069
Primary Metering Rods: 0.042
2nd Rods: CH


Adjust your idle mixture and idle speed to 650 rpms and set timing. redo idle mixture and idle speed a couple of more iterations and have rpm exactly at 650. and see where you are at.

 

[RichRab]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

I would check your firing order and make sure your plug wires are not crossed. Make sure one is in the right cap posistion. Also earlier a couple of posts said the carb was bought at 15. What is that? Good Luck

 

[John_S]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

Also earlier a couple of posts said the carb was bought at 15. What is that? Good Luck

I5 Auto is a supplier of rebuilt/reman carbs.

 

[jy118lfd]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

You will probably need the book to help out on the jetting. It depends on the qjet model. If you got one that is an exact match to the marine, those jets/rods are known. I5 sells car carbs that have been modified to marine. Sometimes they are a different type, and don't use the same rods as others. Metering is different, and will need to adjust based on testing. The one I have is different than typical Merc. If you have the electric choke version they sell, it is probably the same as mine.


Merc varied some between engine models, but this is a common calibration:

Primary jets: 0.069
Primary Metering Rods: 0.042
2nd Rods: CH


Adjust your idle mixture and idle speed to 650 rpms and set timing. redo idle mixture and idle speed a couple of more iterations and have rpm exactly at 650. and see where you are at.

You are right if the carb is unmolested and from a 350 those are the specs. But if this carb were to have been rebuilt who knows what they did. You can disassemble the carb and check all the important orfices with pin drills. You can then see where you are and where you need to go. Most important for the carb is the primary air bleeds as they dictate the size of the jets. For idle problems it lies in the idle air bleeds.

If they converted the carb from an auto carb there is no problem using it but it cannot be jetted to the stock spec. Take a pic and post it of the carb looking down the throat and I will tell you what you have and where to start. There were a million different combos and if it does not match the fuel and air requirments of your engine it will not run right.


If you want you can send me the carb and I can make it right for you. But you are looking at about 200.00 bucks. If you feel comfortable taking it apart then I can walk you through it. Free of charge. I promise I can make you a Q-jet lover

 

[jy118lfd]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

Also dont buy the tool. Take the carb off and take out the screws with a pair of needlenose. Clamp them in a set of soft jaws in a vice and grind a small portion of the top then slot them with a hack saw so a flat head screw driver will suffice. You have to grind them beacuse most were hardended and the hack saw cant cut throught the first few thousanths.

 

[christoner2002]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

I will try to snap a pic of the carb Monday. I ordered a Edelbrock 1409 carb, and spacer, and a new Mercruiser fuel line. I would still like to make the Qjet right, and put that back on once it is right. Figured, it can't hurt to have another carb laying around, as a backup!

 

[christoner2002]

Re: Mercruiser 5.7 troubles. Pulling what hair I have left out

Ahh. I installed my new Edelbrock carb today. All I can say is Beautiful. I am not knocking the Qjet in any way, but I am going to knock the Rebuilder. I5 auto carbs. You Suck! With the new carb, the boat ran great. No bogs, No lean spots. I have told I5 what I would like, and am waiting for a response. If the will refund my money(which I doubt), I will give them their "marine" qjet back. If not, I will see about getting the parts to correct the problems with it. Or I will gladly sell it, as a starting point, for someone to fix. Thank you to everyone for all of your help with everything. It was so nice to go out boating, and just be able to enjoy it tonight. Tonight was the reason I bought a boat again!