Mercruiser hard starting when cold

[2ifbyc]

I have a 1990 mercruiser 7.4 454. She starts right up if she's warm but it takes 10-20 times to start when she's cold. Once I get it started and let it run a couple of minutes and shut it off, it starts right back up. Do I need a new or rebuilt carb? Is there an adjustment I can make? I just did all new plugs, oil change, fuel water seperator, cap and rotor. The boats also been sitting in the water since the end of last season and has some old gas left in it. (About 1/8 tank).

 

[Bt Doctur]

Re: Mercruiser hard starting when cold

sounds more like a choke adjustment

 

[Bondo]

Re: Mercruiser hard starting when cold

I have a 1990 mercruiser 7.4 454. She starts right up if she's warm but it takes 10-20 times to start when she's cold. Once I get it started and let it run a couple of minutes and shut it off, it starts right back up. Do I need a new or rebuilt carb? Is there an adjustment I can make? I just did all new plugs, oil change, fuel water seperator, cap and rotor. The boats also been sitting in the water since the end of last season and has some old gas left in it. (About 1/8 tank).

Ayuh,.... Donno whether you've got the Quadra-jet, or the Weber,.... don't matter anyways,...

They're both known for their bowls to leak off over time, into the intake,......

It takes a few cranks for the fuel pump to fill the bowls, primin' the carb, so the choke will work,...

Rebuildin' yer's might be yer answer,....

 

[2ifbyc]

Re: Mercruiser hard starting when cold

Ayuh,.... Donno whether you've got the Quadra-jet, or the Weber,.... don't matter anyways,...

They're both known for their bowls to leak off over time, into the intake,......

It takes a few cranks for the fuel pump to fill the bowls, primin' the carb, so the choke will work,...

Rebuildin' yer's might be yer answer,....

How do I know which carb I have? Am I better off buying new or replacing? Could it be a fuel pump problem? Someone else told me i may need to adjust the choke.

 

[alldodge]

Re: Mercruiser hard starting when cold

I have a 1990 mercruiser 7.4 454. She starts right up if she's warm but it takes 10-20 times to start when she's cold. Once I get it started and let it run a couple of minutes and shut it off, it starts right back up. Do I need a new or rebuilt carb? Is there an adjustment I can make? I just did all new plugs, oil change, fuel water seperator, cap and rotor. The boats also been sitting in the water since the end of last season and has some old gas left in it. (About 1/8 tank).

10 to 20 minutes when it's cold is a long time. I agree your carb is probably leaking but 10 to 20 minutes is a lot. The best method would be to take it to someone which knows carbs and engines. To do it your self start by taking some pictures of your carb. Find any numbers on it that you can find on the side of it. Give us your serial number

 

[flipbro]

Re: Mercruiser hard starting when cold

Our do you mean 10 to 20 cranks to get her to fire? I had the same issue with my quadrojet on my 5.7. A carb rebuild fixed it rite up. It was exactly what bondo stated!

 

[bonzoscott]

Re: Mercruiser hard starting when cold

When cold not running, look down the carb throat and pump the linkage a couple three times. See if it is squirting fuel. If not, refer back to Bondo's post.

 

[alldodge]

Re: Mercruiser hard starting when cold

My bad, saw times and made it minutes.

 

[2ifbyc]

Re: Mercruiser hard starting when cold

ok took some pics. This is cold and without starting for a week. This is what I got...

 

[alldodge]

Re: Mercruiser hard starting when cold

ok took some pics. This is cold and without starting for a week. This is what I got... View attachment 229024View attachment 229023

I suggest rebuilding the carb kit Merc part No 823426A1
Need to get the numbers off the side of your carb body to ensure exact fit
http://www.iboats.com/Boat-Parts-Accessories/dm/keywords.823426A1

 

[harleyman1975]

Re: Mercruiser hard starting when cold

Also looks as though you need to adjust the choke a bit...just a teeny bit though. You have a quadrajet by the way...with a mechanical choke...NOT manual, not electric, but mechanical choke. If you have not done it before, this is not one to learn on so get the list number off the tag, buy the correct kit and bring it to a good GM mechanic and have it rebuilt.

 

[midcarolina]

Re: Mercruiser hard starting when cold

unless you know the mechanic or he comes highly recommended......having a quad rebuilt is kinda like a box of chocolates.......you never know what you gonna get......

 

[Bondo]

Re: Mercruiser hard starting when cold

unless you know the mechanic or he comes highly recommended......having a quad rebuilt is kinda like a box of chocolates.......you never know what you gonna get......

Ayuh,.... 'n make Sure the guy Knows the bowls are Leakin',....

Also check for throttle shaft slop,...

 

[2ifbyc]

Re: Mercruiser hard starting when cold

Ayuh,.... 'n make Sure the guy Knows the bowls are Leakin',....

Also check for throttle shaft slop,...

What if I just buy a remanufactured one? I see them for about 200 bucks. Is there a different carb I should replace this one with or just match the same one?

 

[bspeth]

Re: Mercruiser hard starting when cold

Why do you sat that Harleyman,I have researched the rebuild some and I was planning on making my Qjet my first rebuild.It didn't seem too difficult,can you point out some common mistakes or sticking points?

 

[alldodge]

Re: Mercruiser hard starting when cold

What if I just buy a remanufactured one? I see them for about 200 bucks. Is there a different carb I should replace this one with or just match the same one?

Buying a rebuild should work fine so long as you get one that matches your engine. The Q-jet has been used on many engines and they just change the jets. Don't want to get one for a 350 or a 454/502 HO. It's good to look for the numbers on the side of your carb.

 

[NHGuy]

Re: Mercruiser hard starting when cold

The primary jets and the secondary fuel rods are the main things that differentiate q jets. So you are far better off rebuilding the oe carb than getting one that's been done and shelved.
BUT, if it truly runs fine when it's warm all you might need to do is get the choke working. It's the 1 x 3" plate on top of the rectangular primary bore. When the motor is cold the little spring on the starboard side of the intake will pull the choke closed. Yours ain't all the way closed in the pic. It's OK to exercise it to see if that frees it up. When the choke linkage is free it will spring softly closed when cold and will stay open when the intake is hot.
Move the choke closed and open, you might be able to push by some minor corrosion and get it moving again. If it just won't move you might want to see if it's disconnected or something. The angle it is at is where they go when the linkage isn't hooked up.

Respect to Bondo but my quadrajet carb book claims the leaking fuel wells were fixed well before your carb came along. And the worn shafts are a lot more common in automobile and truck carbs because driving involves a lot more throttle changing than boating which most folks do at a more steady speed.

Harleyman, that choke isn't manual it's an old school divorced choke.

OP, pump the gas 3 or 4 times right before you turn the key, and if the choke isn't closed you'll need to feather the gas once the motor runs til the motor smooths out a bit. It even helps to feather the gas slightly while cranking too. You can start without the choke, it just takes patience.

 

[midcarolina]

Re: Mercruiser hard starting when cold

IMO that is a very small gap in the choke plate to be causing that severe of a cold start issue.........maybe it's a combination of fuel delivery and choke,
The OP stating once it starts he can let it run for couple minutes then all is fine leads me to believe fuel issue more than choke issue.

 

[NHGuy]

Re: Mercruiser hard starting when cold

Well, I usually fix what I see wrong. Then check my results.
Plus folks don't always pump the gas, nowadays so many grew up with fuel injection!