Issues at idle

ric · **Posted:** Tue Jul 29, 2014 11:11 am

To engage the choke, yes you have to floor it ONCE to engage the fast idle cam, and it will only work if it's below 70* f otherwise the electric choke will not engage the fast idle cam and you just wasted effort. Last I checked it's the hottest time of the year. Choke not needed.

Once the engine is warm, or it's warm outside there is zero purpose to prime the engine. It should start right up. If it's a nice 80 degree day and you goto start your boat and it doesn't start within a second of hitting the key, something isn't tuned right or is dirty. In no way shape form or anything should you have to prime an engine once it's warm. If you're sitting at 140* temp and it doesn't instantly start when you hit the key, something is majorly wrong.

You can make excuses that your boat is hard to start because it has old technology, but that isn't the case. Fuel injection is just better at hiding faults.... until it fails miserably.

LouC · **Posted:** Tue Jul 29, 2014 11:23 am

Ric, ric, ric....
I don't mean to be harsh, but you are too young to understand that, every engine with a carb, is a bit different. Even within the same year sometimes. I have had a lot of cars with carbs:
1962 VW, engine was used in both a Dune Buggy and 65 Beetle. Needed 3 pumps cold
1970 Ford, 302 V8, 2bbl Autolite carb. Needed 3 pumps cold
1972 Chevy 350 V8, 2bbl Rochester. Needed 3 pumps cold
1980 Honda, 1.3 4, 3bbl Kehin carb (piece of crap) needed 3, 4, 6, whatever, it never ran right
1975 Olds 350 V8, 4bbl Q-Jet, 3 pumps cold
1982 Mazda 626 2.0 4, 2bbl carb 2-3 pumps cold
1988 FW with the 4.3, 4bbl Q-Jet, 3 pumps cold

There you have it, my experience in driving cars with carbs, from 1972, to about 1988 when I got my first car with FI ('89 Mazda 323).

in the garage:
9 small engines, some 2 stroke, some 4 stroke, and a 4 stroke Suzuki outboard. They are all different, even 3 Echo machines, they work with different choke settings. The Zuk does not need any pumping. Full choke on one pull it starts, choke off in about 3 sec or it smokes.

The OP needs to make sure his choke works right. It has to close all the way. The vaccum break (choke pull off) has to open it a fraction. He has to manually set the fast idle position with the throttle. If it won't run right before 140*F something else is not right. Idle mix might be too lean.

Oh and all marine chokes are not electric. Mine has a thermo coil on the intake heated by the manifold. Divorced choke in GM speak.

ric · **Posted:** Tue Jul 29, 2014 11:30 am

Your carb is also from 1988. OP's carb is electric choke.

I'm 32 and built my first 350 chevy when I was 15. My father gave me an 82 trans am with no engine, and said here's the parts make it work and you can drive. I've used holley carbs, edelbrock carbs, carter carbs, weber carbs. I professionally raced WKA gokarts and built and tuned my own carbs, ATVs, dirtbikes, motorcycles, lawn equipment, etc.

The 3.0 is a very picky motor and the first thing I would do if I was him, is what I had to do to mine. Insulate the fuel line going from the mechanical fuel pump to the carb. That helps hot starting A LOT. I would also check for timing slip, it can retard and cause hard starting.

LouC · **Posted:** Tue Jul 29, 2014 11:44 am

And he might just have to experiment, some like one pump like you said, some like 3. The problem with later carb motors is that they are jetted too run as well as they could. We had this problem with the little Zuk OB, the jetting was too lean, the idle mix was too lean, it would not run right till the Zuk factory rep replaced the jets and adjusted the idle mixture (EPA has them put caps over the recess where the idle screw lives). After that it started and ran great.

rpengr · **Posted:** Tue Jul 29, 2014 1:10 pm

An engine is not "warmed up" until the inner surfaces of the combustion chamber are hot enough to support smooth running on a normal fuel/air mixture. That is primarily the surface of the piston top, and the inner surface of the cylinder head. Those surfaces might reach 200+ degrees after 10 seconds (sorry, I don't know the real numbers).

An engine is not "warmed up" just because it is 90 degrees outside. Sure, the oil is reasonably thin, but the combustion chamber is not hot.

I still think the OP is having stall issues after initial warm-up, so I think the idle mixture is too lean (probably because of clogged idle jets/passageways in the carb).

Gresh24 · **Posted:** Tue Jul 29, 2014 1:41 pm

The OP may have an issue other than hard starting (idle), which many of the experts here have addressed. But the bottom line is, if it doesn't just fire right up every time after sitting for long periods (or if it needs primed occasionally), it doesn't need a full tune-up.

LouC · **Posted:** Tue Jul 29, 2014 3:04 pm

The reason why you need a choke, is even in warm ambient temps, is as follows:
Your air fuel mixture is sucked in and flows through the intake manifold. Below a certain temperature, some of the gas will condense out of the mixture, due to the cooler temp of the intake manifold. This has the effect of leaning out the mixture, and the engine is reluctant to start. What the choke does, is increase air velocity in the throat of the carb, and that lowers air pressure (Bernoulli's Law folks, physics at work). That lowered pressure draws more fuel out of the carb bowl, which compensates for the leaned out mixture due to condensation. Once the manifold heats up the choke is no longer needed. And that, boys and girls, is why, old fashioned chokes heated by the manifold are better than electric chokes.
Just another little engineering analysis from Lou C....lol....

kd4pbs · **Joined:** Thu Sep 05, 2013 10:34 am **Posts:** 350

Ric is just a one-pump chump. Nothing to be ashamed of, man...

ric · **Posted:** Tue Jul 29, 2014 10:39 pm

kd4pbs wrote:

Ric is just a one-pump chump. Nothing to be ashamed of, man...

As long as I'm happy that's all that matters

fi.na.tine · **Posted:** Wed Jul 30, 2014 12:54 am

Thanks all. Yes - in my 42 years on this planet - this is my first carb'd vehicle. I have worked with many tools over the years with carbs - and yes - they are all finicky about how they like to start. I was just wondering if it taking so much longer to get going than others was unusual. But I will look into getting that insulation for the fuel line, and start doing some more poking around the carb to see if it's my issue.

My buddy was surprised his 96 had EFI, and mine did not.

ric · **Posted:** Wed Jul 30, 2014 6:42 am

The little 3.0 4cly didn't have fuel injection until like 3 years ago from Mercruiser and Volvo Penta stopped selling it due to it's lack of power.

rpengr · **Posted:** Wed Jul 30, 2014 7:27 am

LouC wrote:

The reason why you need a choke, is even in warm ambient temps, is as follows:
Your air fuel mixture is sucked in and flows through the intake manifold. Below a certain temperature, some of the gas will condense out of the mixture, due to the cooler temp of the intake manifold. This has the effect of leaning out the mixture, and the engine is reluctant to start. What the choke does, is increase air velocity in the throat of the carb, and that lowers air pressure (Bernoulli's Law folks, physics at work). That lowered pressure draws more fuel out of the carb bowl, which compensates for the leaned out mixture due to condensation. Once the manifold heats up the choke is no longer needed. And that, boys and girls, is why, old fashioned chokes heated by the manifold are better than electric chokes.
Just another little engineering analysis from Lou C....lol....

I have to disagree with Lou on one point here (say it isn't so :shock:

):

The choke lowers air pressure in the throat of the carb, not by Bernoulli's Principle, but rather by causing a physical restriction to the air entering the carburetor. Bernoulli's Principle is in use at the throttle butterfly, but does not get used at the choke because there are no fuel jets up there to take advantage of it.
Another little engineering analysis from Ray ....lol....

Cap'n Morgan · **Posted:** Wed Jul 30, 2014 8:20 am

ric wrote:

The little 3.0 4cly didn't have fuel injection until like 3 years ago from Mercruiser and Volvo Penta stopped selling it due to it's lack of power.

Nope, totally wrong. The 3.0L engine is still available from most builders.
Four Winns
Chaparral (only engine available in the 18 Sport H2O)
Monterey
Bayliner
Rinker
to name just a few

It will be phased out of the GM offerings in favor of the new 4.5L V6 in the next 2-3 years. The real reason it is used less, is that it is cost prohibitive for builders to offer a C.A.R.B. compliant fuel injected 4 cyl. of this size.
Plus Mercruiser will no longer be sourcing GM blocks for it's marine engines. It has absolutely nothing to do with alleged lack of power.

LouC · **Posted:** Wed Jul 30, 2014 8:28 am

Well Ray, the physical restriction causes the air velocity to increase which lowers its pressure, in the entire throat of the carb. While the whole operational principal of how a carb works is based on Bernoulli's law, the choke merely accentuates that effect temporarily, to keep a cold engine running because of fuel droplets condensing out of the mixture. Its not dependent on precisely where the jets are and in fact in this pic you can see the main nozzle below the choke. The idle jets are below the throttle plate. This is from my Chilton's manual American cars 1970-1977 lol....ancient stuff.

https://www.dropbox.com/s/ncpyim8e196lc ... 20work.bmp

In the end, carb vs EFI, for an older boat I am glad I have a carb. The problem with EFI, is not technical per se. It is the crappy way companies do business. As in, when the product ages, certain parts become No...Longer....Available....(NLA) and then the owner is S....O....L...
I just read about this on Boatered, a guy with a '98 Merc with EFI, had to get a new PCM and get this, Merc discontinued it but was willing to sell him one for $4,000. LOL. He wound up finding one in Cali, for $1500, but I would have converted that to a carb no way I'd give them that cash for a PCM. I got one for my '98 Jeep when it was 15 years old for 400 and that was an OE Mopar one!
With carbs and simple points n condenser ignition, everything is in the aftermarket. No NLA/SOL issues.

ric · **Posted:** Wed Jul 30, 2014 8:58 am

Cap'n Morgan wrote:

ric wrote:

The little 3.0 4cly didn't have fuel injection until like 3 years ago from Mercruiser and Volvo Penta stopped selling it due to it's lack of power.

Nope, totally wrong. The 3.0L engine is still available from most builders.
Four Winns
Chaparral (only engine available in the 18 Sport H2O)
Monterey
Bayliner
Rinker
to name just a few

It will be phased out of the GM offerings in favor of the new 4.5L V6 in the next 2-3 years. The real reason it is used less, is that it is cost prohibitive for builders to offer a C.A.R.B. compliant fuel injected 4 cyl. of this size.
Plus Mercruiser will no longer be sourcing GM blocks for it's marine engines. It has absolutely nothing to do with alleged lack of power.

How am I wrong? Volvo Penta discontinued the 3.0 in 2011. I stated correctly that Mercruiser still offers the 3.0 in fuel injection. Quit being a jerk and learn how to read.

www.iFourWinns.com

Issues at idle

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