Needs help to get started - Merc 350

t_south91

t_south91

Seaman
Joined
May 8, 2014
Messages
52
Hey guys,

I have a '93 merc 350 Magnum that's having a little trouble getting fired up.

At the end of last season, it struggled to idle and start up. Each time I would start, I would have to throttle down in neutral and hold the ignition for 5-7 seconds. It also appeared to run really rich. After each use, I always had a good amount of soot under my swim platform. As well as a smog around the rear of the boat while idling.

SO, I recently dropped it off at my local marine shop where they said they could get me fixed up. This included a rebuilt carb, among other service items on the outdrive.

The problem is that they didnt FIX it...the boat idles now as it should, but it still has difficulty starting up. I still have to throttle it down in neutral and hold the key for 3-4 seconds until it turns over.

Before I call them and say they didnt fix my issue...I want to make sure that I am not crazy. Should I run the remainder of last seasons fuel out of it first, give it some time to flush everything out of the system? I was under the impression that a carb rebuild would solve this issue immediately.

All input is appreciated!
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,088
Ayuh,..... If this is a carbed motor, I don't see a problem,....

If it's Efi, it might have a problem,....... or not,.....

3 or 4 seconds ain't a long crank time,....
 
t_south91

t_south91

Seaman
Joined
May 8, 2014
Messages
52
It is a carbed motor.

But I wouldn't think that I should have to throttle it down in neutral for every start (especially if its a short time between starts). Or should that be expected with a carb? Also, what about the soot? Do you not think its running to rich?

Thanks for the reply.
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
What do you mean by throttle it down?? Throttle down means Idle. Throttle up means more throttle. Turn over means engine rotates by the starter but does not start. If you still have soot build-up after a new carburetor, choke operation is suspect as that was probably the problem in the first place. So what exactly is your cold and hot start procedure?
 
JASinIL2006

JASinIL2006

Vice Admiral
Joined
Feb 10, 2012
Messages
5,715
I have a '97 carbed 350 Mag that requires a bit of throttle to start when the engine is cold, but it starts easily and without giving it any extra gas when the engine is warm. Once warmed up, a quick turn of the key is all it takes to restart.

I don't think it's unusual for a carbed engine that is cold to need some cranking before it catches, but once it's warm, it seems like it ought to fire up right away without goosing the throttle.
 
K

keith2k455

Chief Petty Officer
Joined
Jul 23, 2012
Messages
558
Actuating the throttle on a carb allows the choke to set. Some will need this done with every start and others only when cold. I don't see a problem with either as long as it starts without flooding or too much work. I wish mine started that easy cold and I think mine is fine.
 
F

flipbro

Master Chief Petty Officer
Joined
Feb 8, 2013
Messages
830
Black soot on start up is a problem! Choke or set to rich.
 
t_south91

t_south91

Seaman
Joined
May 8, 2014
Messages
52
Thanks guys.

My start up process is as follows.

When cold: Put the throttle in neutral, and push all the way down 2-3 times. Boat fires right up.

When warm: Simply turn the key. I have to hold the key for a while and it just continues to try and turn the engine over. Instead of holding it for 10 seconds. I put the throttle in neutral and push forward 1/4 of the way down. Boat starts up. I realize its not a EFI motor, but still.

I feel that when the boat is warm, I should be able to just turn the key. I classify the boat as warm when I have the engine shut down for NO LONGER 30 minutes. So from 0 - 30 mins the engine should still be warm. Correct me if I am wrong. I live in Arkansas so its not exactly cold here during the summer. Water temp averages 80 - 85 in the summer months.

Now, my question is how do I adjust the choke or change the setup to make is "less rich"? And what happens if this doesnt get addressed soon? Because the motor ran "rich" all last season.

Again, thank you guys. I appreciate everything.
 
K

keith2k455

Chief Petty Officer
Joined
Jul 23, 2012
Messages
558
by your description, I say you have no problem. That's very similar to my starting process, which really isn't that bad. If you were having to pump the throttle multiple times to get it to catch or if you flooded every time, I would look deeper.

The next time you start your EFI car warm, pay attention to the rpm. It does idle high for a short while, so giving a little throttle to your warm boat engine with a carb isn't any different.
 
NHGuy

NHGuy

Captain
Joined
May 21, 2009
Messages
3,631
I have a 97 with a weber 4 bbl. If i shut it off warm it will fire back up on the first compression pulse.
But after it has set for half an hour it needs a little pump of gas and 2 to 5 seconds crank. I think the fuel in the intake tract must evaporate with the breezes and heat in summer, and it gets new fuel from the carb.
Remember, a carburetor engine is vapor fueled from 8 to 20 some-odd inches away from the combustion chambers.
 
F

flipbro

Master Chief Petty Officer
Joined
Feb 8, 2013
Messages
830
I run a four barrel quad and after its fired up once I can shut it down for hours and it will fire on the first compression pulse. Are the Weber a little more temperamental?
 
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