7.4 Merc really hard starting

seasure1 · May 21, 2007

Well I was hoping someone had this issue and has a solution.
Mercruiser 7.4 with Weber Carbs, It is really hard to start. New everything
compression great new plugs wires rotor cap, carbs rebuilt by a carb "expert". The rebuilder I had used in the past. Engines smoke, stumble hard to start cold, tried adjusting choke idle screws etc. I have seen other threads about this but I really need some help!!!

Coors · May 21, 2007

Re: 7.4 Merc really hard starting

What color is the smoke?

180shabah · May 21, 2007

Re: 7.4 Merc really hard starting

Perhaps it is time to check the work of your "expert".

Set choke pull-off to 1/8"
Float level should be 1-9/32"
Float Drop should be 2"

seasure1 · May 21, 2007

Re: 7.4 Merc really hard starting

Black smoke and once the engine warms up it runs great!!! I was thinking of replacing these Webers with new Edelbrock 1410 carbs.

180shabah · May 21, 2007

Re: 7.4 Merc really hard starting

OK, it is black smoke, but everything is fine after it warms up. Readjust the Choke. The Weber is the same carb as the Edelbrock, So if you replace it, it will still need to be properly adjusted.

seasure1 · May 21, 2007

Re: 7.4 Merc really hard starting

Tried the choke adjustment route, same results also checked the voltage to the choke that was fine also

Don S · May 21, 2007

Re: 7.4 Merc really hard starting

Describe exactly what you do to cold start the engine. Leave nothing out.

seasure1 · May 21, 2007

Re: 7.4 Merc really hard starting

I have tried all methods that I know Don. I have tried just turning the key without touching the throttles. Most of the time they will not start. Sometimes they run for about 10 seconds then die out. I have tried pumping the throttle. I have tried one time two times three times. Wide open throttle as well. When the engine finally does start I quickly have to grab the throttle and advance it. At this point the engine is running extremely rough black smoke etc. Once the engine gets to about 120 degrees then the choke opens. Then the boat operates normally. Thanks Don for your help.

Don S · May 21, 2007

Re: 7.4 Merc really hard starting

Try this for your adjustment.
With the engine cold, loosen the 2 screws around the electric choke and turn it so the choke plate opens.
Then turn it so it JUST closes the choke plate. Tighten the screws and give it a try.
When you do start it, pump it a time or two, then keep the throttle up to about a 1/4. When it starts, keep the idle rpm around 1000 to 1500 rpm till it starts speeding up. Then pull it back to around 1000 and let it idle.
It's a carb on a big block, not EFI. And big blocks are cold blooded.

seasure1 · May 21, 2007

Re: 7.4 Merc really hard starting

thanks Don I will let you know tomorrow!

seasure1 · May 22, 2007

Re: 7.4 Merc really hard starting

Don,
I tried what you said but no difference. Purchased two new Edelbrock carbs model 1410 which are direct replacement for the Webers. Bolted them on. Starts great going for a sea trial later.....

seasure1 · May 22, 2007

Re: 7.4 Merc really hard starting

Well so much for the expert carb rebuilder. Replaced with new Edelbrock 1410 all is well!!! Easy start running great. Another problem solved!

7.4 Merc really hard starting

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