Idling Too Fast

[mike7a10]

OK...I feel like a dope! I feel like I should be able to figure this out without any assistance...but...here I am!

I have been trying for a few weeks to get my carburetor to idle correctly. A few weeks ago I posted a question as I had sucked water into the engine and ultimately into the carb. I had pulled carb apart 3 times and also completely drained the tank and I got her running pretty good. I was pretty happy to get her running again and the engine is running smoothy and I have no problems other than a fast idle.

Since then I have been trying to get the idle correct. I have tried using the idle adjustment screw (numerous times) and I seem to get it too lean and it bogs down. I back it out a little and it idles nicely but too fast. I am running around 1000 rpm cold and 1200 rpm warm. I have also adjusted the arm for the throttle to extend or push the thottle further forward to manually adjust the reach of the throttle and that helped but I am still idling around 1200 rpm warm (it was faster before this adjustment).

I am also noticing that I used to be able to hit around 2300-2400 rpm but I can only get her up to about 2100 rpm now. This could be some crud on the prop and bottom due to saltwater growth but I had the bottom cleaned about 4 weeks ago. (The water temp in our marina here in SW Florida is currently around 84 to 86 degrees and we don't have a great deal of circulation that leads to some pretty quick bottom growth.)

I don't know guys...I do have one theory...when I constantly had to drop the carb due to the saltwater intake I reused the gaskets all 3 times. I have since ordered new gaskets that I can install. I am wondering if the main bowl gasket is letting in too much fuel? I understand that it is hard to flood these carbs and it if I am getting too much fuel in the carb it may be masking it while underway, etc. It just seems to me that if it was the main gasket it would not run smoothly otherwise.

My other thought is that this could be a jet issue? I removed the idle jet to spray carb cleaner when I had to remove all of the saltwater...I wonder if I could have caused an issue with that...but that seems unlikely as I can adjust the idle screw and it responds OK.

To tell you the truth I was thinking of leaving it well enough alone because it is running smoothly otherwise but I think I am using way too much fuel.

Any suggestions or ideas are definitely welcome!

Mike
S/V Plan Sea

[mike7a10]

Idling Too Fast Continued

After I wrote this post I went down to the boat and began fiddling with the engine settings some more.

I have discovered that if I screw in the idle adjustment screw clockwise or all the way in the engine continues to idle. I am thinking this is a sign that I am getting air in the carb throught the gaskets and need to replace them.

Any thoughts?

Mike

[smosher]

If I remember correctly turning it clockwise increases rpm and turning it counterclockwise decreases rpm.

Are you sure your turning the idle rpm adjustment or the idle mixture
adjustment ?

I think you might be adjusting the mixture instead of rpm's.

Steve

[Dave Neptune]

Idle

Mike, adjust the Idle speed screw all the way out which will close the butterfly valve completely and check. If it still won't slow down you have a vacuum leak behind the carb somewhere, also make sure the scavange tube is tightened so it doesn't leak either. The idle speed screw should be able to bring the rpm's down enough to stall the engine.

After you replace the gaskets if they are indeed leaking you should have no problem getting her to idle!!

Also are you using a PCV kit? If so it could ba a source of to much air getting into the intake manifold if it is faulty. You can just block it off temporarily to test.

Dave Neptune

[Marian Claire]

Yes to what Dave says. One of the many things I found during, Persistance pays, was that the idle adjustment had no effect. Check for air leaks in the carb or carb to manifold connection. Dan S/V Marian Claire Long day in the bilge of another boat, but the cruising fund is getting fatter, or more like normal weight

[mike7a10]

Thanks guys. I am going to check all the fittings (gas lines, scavange tubes, etc.) before I pull the carb. Good idea on opening up the idle screw all the way out...

I do not have the PVC kit on mine so I can eliminate that.

I will probably have to check the carb sometime later this week. I will let you all know what I find.

Thanks again everyone.

Mike

[Dave Neptune]

Idle speed screw!!!!!

Mike, make sure that it is the "Idle speed screw" that you back out not the mixture screw on top of the carb.

Remember the mixture screw adds air not fuel to the mix~~~I E~~ open is leaner (more air) and in is richer (less air), the amount of fuel is metered by the idle well-jet.

David

[mike7a10]

Update-Success!

Sorry it took so long to reply with an update as I wasn't able to get back to service the carb until this past (4th of July) weekend...I'm not sure if anyone who was kind enough to offer advice will see this but I said I would send an update.

I dropped the carb and replaced the gaskets and reattached. I started her up and and after fiddling with the timing I kept adjusting the idle speed screw without success of lowering the idle rpms. It dawned on me that maybe the throttle connection could be extended just a bit and with a few turns and presto! The engine is now idling at around 750 rpm and rev's up to 2250 at WOT under load.

The engine is running as smooth as ever and with the correct timing is giving me lots of power. Got the old girl, a 32.5 Irwin (13,000# displacement) up to 6.4 knots at 2250 rpms...

I am glad I replaced the gaskets in the carb as the engine is really running much smoother now (I am convinced some air was getting into the carb causing it to run with a weird hesitation or 'bump' about every 3 seconds...)

So all is well in Punta Gorda, FL. Thanks again to everyone who has helped me with this issue as well as all of the other times I have gotten great advice from all of you fellow "A-4 Heads".

Mike
s/v Plan Sea

[sastanley]

Mike,
Nice work, thanks for the update! Posts like this give us all hope that we can get ours running as smooth as someone else's.

Although I know my carb is clean and I have brand new gas (& tank) I am wondering if an air leak around a gasket could be causing some of the issues I am experiencing, which are similar to what you were experiencing prior to the fix.

Time for more tweaking!

[Mark S]

Mike, what do you have for a propeller?

Mark S

[mike7a10]

Hi Mark...I purchased the Indigo prop a few years ago and it made a huge difference for me. When I bought the boat it had a traditional 3-blade prop (I think around 12"-13"?) and the engine was not able to get above about 1600 rpm with a top speed of around 4.8 knots.

It has definitely been one of the better purchases that we have made. The speed I mentioned above (6.4 knots) was on a slack tide with an 8 mph wind pushing us a little bit.

Hope this helps!

Mike

[Mark S]

Yes, Mike, this is very helpful. Your Irwin displaces the same as our Pearson and is the closest comparison I've been able to make. I've been all over various sites trying to find other owners of Pearson 35's with A4's to learn what prop they use but with no success. I think we are the only Pearson 35 left with an A4!

I'd feel ever so much better if I could cruise under power at 6+ knots and 2250 RPM. Is your prop in open water or in an aperture? Ours is in an aperture.

Mark

[mike7a10]

Our prop is not in an aperture and is open water.

FYI:

Draft 3'11"
Beam 10'0
Length 32.5'
Displ. 13,000# (closer to 14,000# will topped off fuel/water tanks, gear, etc.)

The Indigo prop is probably a bit smaller than what you currently have. When I first got it I was surprised how small it was compared to the old prop and I had doubts when I replaced it. But the small size really helps the engine get up to higher rpms.

By the way...I rarely "cruise" at 2250 rpms as that is wide open throttle for me. I typically run the engine around 1700-1800 rpms and that pushes me around 5.0 to 5.5 knots. Keeping the bottom clean really helps out as I will lose some speed especially in the hot summers down here as the sea growth gets out of control then. Keeping the prop clean also helps out tremendously. It is amazing how much speed you can lose when the prop is only fouled a little bit due to sea growth.

Mike

[Mark S]

Mike,

The notion of a fouled prop keeps popping up and I keep pushing it out of my mind. I guess I shouldn't do that, and instead I should go down and look and scrub it up a bit.

Does anybody in the community run the Indigo prop in an aperture between the keel and the rudder? Maybe I should start a thread about this.

Mark