low idle

steadyon · 06-28-2009, 09:04 AM

Hi all,
Our boat is a 2004 pontoon with a 90 Merc.
This season, (although only been out 3 times so far!) the engine is not idling well and when it does its very rough or it will stall. It does start back up and seems to drive fine. Do any of you mechanical minds have any thoughts?
Maybe the idle needs adjusting or spark plugs need changing?
Thanks

Seeker · 06-28-2009, 09:28 AM

Could be a water related problem. Have you checked your filters for any accumulation?

steadyon · 06-28-2009, 09:40 AM

I am not mechanically inclined. What filters are you referring to?
I guess I should have my mechanic take a look at it.
thanks for your input.

Airwaves · 06-28-2009, 06:14 PM

Now that E-10 fuel has arrived at the lake you should make certain that you have a water seperator in your fuel line. It's easy to install on an outboard if you don't already have one.

Ethanol, among it's other issues with boats, attracts mosture and if you don't use your boat often (3 times this season would probably fall into the not often category) then the mosture will begin to seperate from the gasoline creating water in your fuel. Water being heavier than gasoline will sink to the bottom of your tank where you engine draws fuel causing problems.

Replace your water seperator filter, your gasoline filter and don't forget to add a stabilizer formulated to counteract ethanol every time you refuel. Also keep your fuel tanks topped off, this leaves less room for mosture to form when your boat is not in use.

If the problem still doesn't clear up then you may have to rebuild your carbs and flush out your fuel tanks. This of course assumes that the problem is not tune up related. Make sure your plugs are not fouled and if they are replace them.

Good luck and don't forget to link onto the NMMA website to express your opposition to increasing E-10 to E-15, the date for the close of public comments is quickly approaching.

NoBozo · 06-28-2009, 07:09 PM

Airwaves is pretty much on the money. One step further: Ethanol gas left in the tank over the winter is DEVASTATING to your Carburetor. It may likely need Carburetor overhaul to remove SLUDGE. High speed operation may seem fine...Low speed (idle) is where the problem will manifest itself.

Fuel Injection seems to be much less susceptible to Ethanol problems because it injects fuel at High Pressure.

steadyon · 06-29-2009, 12:55 PM

Thanks all,
I will check with my mechanic.
will let you know what he says.

06-28-2009, 09:04 AM	#1
steadyon Senior Member Join Date: Jan 2007 Location: Meredith Posts: 102 Thanks: 0 Thanked 7 Times in 6 Posts	low idle Hi all, Our boat is a 2004 pontoon with a 90 Merc. This season, (although only been out 3 times so far!) the engine is not idling well and when it does its very rough or it will stall. It does start back up and seems to drive fine. Do any of you mechanical minds have any thoughts? Maybe the idle needs adjusting or spark plugs need changing? Thanks

06-28-2009, 06:14 PM	#4
Airwaves Senior Member Join Date: Feb 2006 Location: I'm right here! Posts: 1,153 Thanks: 9 Thanked 102 Times in 37 Posts	Gotta love that Ethanol! Now that E-10 fuel has arrived at the lake you should make certain that you have a water seperator in your fuel line. It's easy to install on an outboard if you don't already have one. Ethanol, among it's other issues with boats, attracts mosture and if you don't use your boat often (3 times this season would probably fall into the not often category) then the mosture will begin to seperate from the gasoline creating water in your fuel. Water being heavier than gasoline will sink to the bottom of your tank where you engine draws fuel causing problems. Replace your water seperator filter, your gasoline filter and don't forget to add a stabilizer formulated to counteract ethanol every time you refuel. Also keep your fuel tanks topped off, this leaves less room for mosture to form when your boat is not in use. If the problem still doesn't clear up then you may have to rebuild your carbs and flush out your fuel tanks. This of course assumes that the problem is not tune up related. Make sure your plugs are not fouled and if they are replace them. Good luck and don't forget to link onto the NMMA website to express your opposition to increasing E-10 to E-15, the date for the close of public comments is quickly approaching. Last edited by Airwaves; 06-28-2009 at 06:17 PM. Reason: suggesting tune up as well

06-28-2009, 09:28 AM	#2
Seeker Senior Member Join Date: Nov 2007 Location: Effingham Posts: 408 Thanks: 37 Thanked 19 Times in 15 Posts	Could be a water related problem. Have you checked your filters for any accumulation?

06-28-2009, 09:40 AM	#3
steadyon Senior Member Join Date: Jan 2007 Location: Meredith Posts: 102 Thanks: 0 Thanked 7 Times in 6 Posts	I am not mechanically inclined. What filters are you referring to? I guess I should have my mechanic take a look at it. thanks for your input.

06-28-2009, 07:09 PM	#5
NoBozo Senior Member Join Date: Jun 2008 Location: Portsmouth. RI Posts: 2,231 Thanks: 400 Thanked 460 Times in 308 Posts	Airwaves is pretty much on the money. One step further: Ethanol gas left in the tank over the winter is DEVASTATING to your Carburetor. It may likely need Carburetor overhaul to remove SLUDGE. High speed operation may seem fine...Low speed (idle) is where the problem will manifest itself. Fuel Injection seems to be much less susceptible to Ethanol problems because it injects fuel at High Pressure.

06-29-2009, 12:55 PM	#6
steadyon Senior Member Join Date: Jan 2007 Location: Meredith Posts: 102 Thanks: 0 Thanked 7 Times in 6 Posts	Thanks all, I will check with my mechanic. will let you know what he says.