Is this normal?-gctid372629

[Guest]

Ok boat is a 2001 285 with a Merc 5.7 with 2BBL carb.

Here is my question, when the engine is cold it will not idle, once fully warmed up it idles fine, and for the rest of the day even when the engine has cooled I can just turn the key and go. Once the engine is warm, that is fully up to normal running temp it also idles fine, she starts easy, no problems there.

Tried disabling the Choke, (disconnected and chock plate held fully open, opens fully once warm when connected anyway) engine again starts fine without choke and just a pump of the throttle.

Not really a big problem just wondered if anyone else had seen this?

[Guest]

gretzky wrote:
Ok boat is a 2001 285 with a Merc 5.7 with 2BBL carb.

Here is my question, when the engine is cold it will not idle, once fully warmed up it idles fine, and for the rest of the day even when the engine has cooled I can just turn the key and go. Once the engine is warm, that is fully up to normal running temp it also idles fine, she starts easy, no problems there.

Tried disabling the Choke, (disconnected and chock plate held fully open, opens fully once warm when connected anyway) engine again starts fine without choke and just a pump of the throttle.

Not really a big problem just wondered if anyone else had seen this?

Some engines may be a bit cold blooded, but it is not normal it should be able to idle.

[Guest]

May be time for a carb rebuild. The idle jets could be clogged.

[TerryW]

gretzky wrote:
Ok boat is a 2001 285 with a Merc 5.7 with 2BBL carb.

Here is my question, when the engine is cold it will not idle, once fully warmed up it idles fine, and for the rest of the day even when the engine has cooled I can just turn the key and go. Once the engine is warm, that is fully up to normal running temp it also idles fine, she starts easy, no problems there.

Tried disabling the Choke, (disconnected and chock plate held fully open, opens fully once warm when connected anyway) engine again starts fine without choke and just a pump of the throttle.

Not really a big problem just wondered if anyone else had seen this?

My 5.0L 1998 is exactly the same.

Also, the boat is in the water all year round and subject to condensation etc. If I don't start the engine for a few weeks it becomes obstinate. You would image that there is a hard fault like water in the fuel but there isn't.

[Guest]

Thanks for the quick replies, the boat is also in the water all year round. May take a little time to re-build the carb, had it apart last year due to tiny bit of crud causing the float valve to stick so know my way around it with no problems. (The engine has always been like this though, its not something that started after that)

I work in IT and spend all my time sat in from of a computer its nice to play with real bits of hardware at the weekends, just wish I could use a hammer on the computers sometime too!

[Guest]

gretzky wrote:
Thanks for the quick replies, the boat is also in the water all year round. May take a little time to re-build the carb, had it apart last year due to tiny bit of crud causing the float valve to stick so know my way around it with no problems. (The engine has always been like this though, its not something that started after that)

I work in IT and spend all my time sat in from of a computer its nice to play with real bits of hardware at the weekends, just wish I could use a hammer on the computers sometime too!

lol, on my desk there is a hammer "PC REPAIR". Everyone in IT should have one, today we are going to sledge hammer a cisco router that caused too many long nights

[richardson]

Am I reading this right - that if you hold the choke open when cold it starts and runs with just a pump of the throttle? If so the choke needs to be adjusted so that it opens sooner.

[2850Bounty]

If the low speed metering circuits allow it to run and idle when warm, I'd say that the issue is with enrichment during cold start-up.

Is it safe to asssume that this carburetor uses a conventional style choke?

Electric helix heating element to open it?

Any adjustment to the choke plate, should be done when cold, and prior to any power to the helix heating element.

Once the element begins to warm the helix, it will make it difficult to adjust for a cold setting.

When fully warm, there should be some mild tension wanting to hold the choke plate open.

Just try several adjustements, and you'll eventually get it.

You could also try closing off the low speed air screws a bit.

By closing off the air screws, you'll richen the low speed fuel metering.

No much... just a little, and remember where they were so you can return to this setting if need be.

.

[TerryW]

If I remember rightly, there was a thread a few years back where a few people were disabling the enrichment on their carb and relying on a few throttle pumps to get started and leaving the throttle open a little (1200 rpm) until the engine was warm enough to reliably tick-over and shift into fwd and rev (a check that should always be run before untying).

I still do this with the choke enabled. I don't know how they disabled the choke though. I think it just got wired open.

Terry

[Guest]

If I'm reading this correctly, you have confirmed the choke goes full open, but you haven't confirmed it's going full closed when cold. Have you checked that? After that, then you need to get into the carb's idle circuit as described above.

[88fourwinns]

what is your cold start procedure? Many marine carbs that use old school automatic chokes (not the Merc TKS system) require that you open the throttle all the way before cranking the engine over (this allows the choke to close all the way, which is what you want for a cold start). Then, you have to advance the throttle lever foward to about 1/4 throttle to provide the necessary fast idle to keep it running on the choke. When the engine starts, look at the choke plate, it should open a fraction of an inch (this is called choke pull off or the choke unloader). If not the engine will run too rich and may stall.

The part that confuses people is that you must adjust the fast idle with the throttle lever, it does not happen automatically even though it's an automatic choke. On old school cars, depressing the gas pedal all the way let the choke open and also set the fast idle. Not so on most car engine based inboards and I/Os.

[CaptTom]

Just to throw one more thing out there, I've found that engines can get cold-blooded when they need new plugs and wires. All of the above is still true, but I've cured many a cold starting problem that way, too. If it's due for plugs and wires anyway, it's an easy thing to eliminate.

[dmcb]

If it idles good when its warm you don't want to start adjusting something that isn't broke.

Look at the choke when its cold. Move the throttle to set the choke and see what it does. The choke will not set unless the throttle is moved with a pump on most carbs.

Many today do not know how to operate an engine with a carb. Its been a generation since a car had one, maybe two.

To start an engine with a carb.

Pump the throttle a couple of times. You have to bypass the shifting if the throttle control does both. The number of pumps is different with different engines. To many times and it floods. Adjust the pumps as needed.

Leave the throttle open a bit so it runs fast when it starts. Maybe 1000 rpms.

When it warms up a bit, bring it back to idle.

If you think you have flooded it, hold the throttle wide open (don't pump it) and crank the engine. When it starts be quick to bring the throttle back.

Try that and see what happens.

I was on a 3055 one time. The owner was going to start the engines. Crank, crank, crank. No start. I said pump the throttle a couple of times. Varoom. His wife says do the same for the other engines. This had been going on for the entire time they owned the boat.

Doug

[88fourwinns]

So you see being older has its advantages, I do my own lanscaping and have a garage full of small engines, 3 4 stroke machines and 4 2 stroke machines, and the latest addition a Suzuki 2.5 hp outboard for our dinghys, all with carbs and each one starts a little bit different. I am sure that my early years of driving carbs helps me get all these engines to start.....

[TerryW]

Starting procedure:

When the engine is in more or less frequent use: 2 pumps of the throttle. Leave the throttle 1/4 open. Wind the engine for a few seconds until she fires. Adjust the throttle to 1200 rpm until warm enough to go in and out of gear at idle without stalling. When gear changes are ok consider untying and getting underway (and not until then).

When the engine has been left for a month or two without starting (dumb, I know): 4 pumps. wind till she fires and the rest as above. If she wont start but makes half-hearted attempts: leave the battery charging for a couple of hours and try again. Wind until she gives up being a pig and starts. Plus, I no longer get tempted to change everything on the engine as I know there is nothing wrong the engine. It is just being a pig to punish me for leaving it so long. They only pretend to be inanimate objects.

If you manage to flood it when it has been run regularly that is really unlucky. They can flood quite easilly if you keep pumping when they have been left for a while. In both cases as Doug says just leave the throttle wide open and wind. Eventually, they splutter into life and then rev like crazy. You want to have your hand on that throttle to avoid over revving a cold engine.

Hope that helps. . . .

PS I use the excuse that the engine needs to be run to get a day on the boat. It works for me. . . .