about to give up
 

Ok guys yet another problem ugh.... ok i got my motor to fire but i cannot seem to get it to idle down. It will run at 1500 and soumds great, i have adjusted the air fuel mixtures, the idle screw throttle cabe, everything. And without getting it to idle down i can really ajust the timing. I got it to come down to a grand bit as soon as i brought out the timing light and started adjusting the timing it died. After a grand it just comoletely dies. Im lost thinking i may have a bad carb thats my guess. Any helo would be appreciated. Mercruiser 260, vortec heads, performer intake, quadrajet 4 barrel thru hull exhaust

Vacuum leak. Check your intake manifold and carb gaskets. Put a vacuum gage on it and check it out. Spray some carb cleaner around those areas and see if the idle changes, but if it is leaking air on the bottom side of the intake, most likely area it will not show up doing this. But a bouncing needle will tell you the story.

Everything except the carb is brand new and its running a como cams 262 cam i forgot to mention that. All gaskets are new and everything is tourqued to specs. Could it have a leak with in the carb or maybe even have a bad float? ?? And i have the edelbrock adaptor plate on the intake plus a thicker carb gasket could that be an issue

The Vortec intake gaskets are easy to over tighen. Also double check the initial timing...could be off enough to idle up tat high. My money is on a vacuum leak. While its running spray wd40 arond the carb base and the intake gaskets.

Sounds like a vac leak to me also. Check the carb base gaskets, intake gaskets again

John jr

Just a thought, you might check the gasket between the throttle plate & the carb body. It can get crushed on the primary side if the screws loosen on the back side & the bolts are too tight on the front. Randy

how many times did you go over the intake bolts?? just once wont do it,,15 ft lbs and thats it with blur loctight on the threads.. or they will loosen up..you have to go over then like 5 or 6 times to get all the bolts to 15 ft lbs,,also their is 2 differant style merc carb gaskets one will make a Q-jet leak causing a vacume leak..take the carb off and flip it upside down and match the gasket to the base of the carb,,you will see where it would leak vacume ..

Just throwing it out there,, since you have the Vortecs, which intake gaskets did you use?

I dont know the brand my engine builder gave them to me i think they were rubber coated and ss steel.

Just double check to make sure your throttle cable is not way out of adjustment at the barrel end which is not allowing the carb linkage to fully return. Unhook it to see if anything changes. if not most likely U have a vacuum leak.

Sounds like the wrong base gasket.
Or float set to high.

I'm going to agree with everyone else. It's most likely a vacuum leak, just because everything is new doesn't mean anything. Do as others have suggested and I bet you will resolve your problem. Good Luck!

I hope it is justa vacuum leak. I called all over for a new carb and i swear there is a carb shortage right now lol i just got off work so im going out now to pull the carb and check all my gaskets and tourque settings on everything. Summer is almost over and i just wanna go out on this thing, its such a beautiful boat. How do u post pics on here i wish u all could see it.

In all seriousness...I chased a vacuum leak on one of my Vortec Chevy's I put together for my boat until I discovered that I had a sand hole in the number 8 intake runner. I'm not saying you do and it has never happened to me in 45 years experience...but it happens. I replaced the intake manifold with another one and the problem went away.

Keep an open mind.

don't the vortec's use plastic spacer with orings. remember some gaskets don't cover ports properly, bottom side leaks,

Well looks like i found the problem. I ussually dont let ppl help me cause when they do they say they tightened the carb down and didnt lol. Please god i hope this is the issue. Put a new gasket on tightened down correctly pulled it out on the drive way amd started her. Was able to get it to idle down to around 750 800 ish. I think once i get it in the water a little more fine tuning i cam get down under 700, which is where i would like to be. I got the timing down to 8 dbtdc. I think i need to play with the air fuel screws once i get it in the water to get it just right. I still want to get a new carb with an electric choke since i cannot run the divorced choke with my vortec intake. I think that would help with the hard starts. With all the money i spent this season thus far if i can get this quadrajet to last i will upgrade in tje off season, along with new exhaust. Thank u everyone for all ir help this site is great. I really appreciate your time

I also try to do everything myself. I have had similar experiences with people "helpng". Hope the simple fix is all it was.

Jeff

BTW, are you going to the old school reunion saturday at Brownies? I should be there with my Scarab.

i have a holly on my boat and have not needed a choke in the summer for over 25 yrs...you really dont need it,,i pump twice and she fires,,i set the throttle for 1200 rpm's for a few minutes and im on my way..

Sbslinde whats the old school reunion