Motor idle/starting issues

[Chamelion]

2002 Mercury 40hp 2 stroke

Prior to doing a de-carb a few weeks ago I had none of these problems...

She'll generally start first or second pull and will idle all day on the muffs, but plop her in the water and it's a whole different story.

Prime bulb - start motor, sometimes it'll idle for a fair while, other times less than a minute. It will idle normally before seemingly starving itself of fuel and then cutting out. At this point the bulb is always empty, bone dry, or so it seems.

Prime bulb again - then it'll usually take a good 5-7 pulls before it turns over and kicks into life. On the third or so pull it'll sometimes splutter and cough momentarily.

If I'm sitting at anchor or on the electric I'll generally always have to re-prime it, even if it's only been a few minutes and again, it usually requires a few pulls.

I've checked the timing to be 2 degrees post TDC at idle, though I've tried dead on 0 degrees as well. I've also had a mechanic check the sync of my carbies and the idle screws. I toyed with the screws a little today for some very minor improvement, but nothing ground breaking.

I've replaced the bulb and I've checked the fuel lines for obvious holes.. I couldn't see anything. I've also tried running the bulb horizontal and vertical with both the arrow up and the arrow down.

Interestingly, today, I went to tilt the motor up a bit (pickups still under water) and it cut out... co-incidence? I'm not sure.

Appreciate any help

Cheers.

ps: Runs fine otherwise. Returned about 2.9km/L on my fully decked out and rather heady quintrex dory turning a very worn out prop.

 

[oldman570]

Re: Motor idle/starting issues

Some where the fuel system either has a fuel blockage or air leak, or the carb floats are sticking shut from the way you say it is acting. Might have a blockage in the fuel vent on the tank, or bad conector or clamps on the fuel hose. The motor should be equipted with a mercury switch, that will kill the motor if it is tilted up to far, to where the motor should be out of the water. That is a safety to keep from a overheat alarm and causing damage from that condition. Use a diffrent tank and hose to see if the they are the trouble or if it is on the motor. Could be the fuel pump needs rebuilt if the primer bulb dose not calopse and stays ready to prime. Fuel pumps will get to where they will pump enought fuel for the motor will run at idle but not at higher RPM. If the hoses, and all rubber components, are ones that are not ethenoal resitant and you use that fuel it has a tendancy to cause trouble over time. New hoses, and rebuild kits are made to handle the ethenoal fuel. The timming should be set at spec for the motor as damage, burnt pistons, can be done if set to fast. JMO
Oldman570

 

[Maxz695]

Re: Motor idle/starting issues

I agree check the tank vent. Blow into the hose that leads to the tank pickup. If there is blockage in the vent or hose to the vent it should be apperent or clear out at that point. Set the carb screws at 1 1/4 out from a light seat. Then adjust for best idol. There may be water intrusion through the exhaust cover and baffle due to corrosion or a bad gasket which lets water into the exhaust port mixing with the fuel causing it not to start or run rough. sputter or even backfire. This happened to my 79 40 2 stroker. I replaced the cover and baffle.The baffle had corroded through. I upgraded to a 70 HP and parted most of the 40 out. The only pic I have is my ebay add and pretty sure they will not work on a 2002. But for reference I,m posting them. Exhaust cover 55157 and divider plate | eBay <EDIT> As started in the next post if it aint broke don,t fix it. The exhaust senerio is a worst case explaination of the symptoms you described and should only be looked at if the problem persists over time. Decarb will tend to remove carbon from the rings and piston domes which will tend to foul the plugs. I suggest a second set of plugs and constant cleaning of the plugs until the decarb removes all the crap inside the cylinders. This is also why I stated to check the air flow through the tank first then move on to hoses clamps fuel pump filter etc etc.

 

[Texasmark]

Re: Motor idle/starting issues

If all you changed was doing a decarb and have run the engine before, which you said, then I wouldn't go looking for non-related causes.

My opinion is that the decarb knocked something loose that is floating around and you never know where it will land next, nor how long it will stay.

If you subscribe to the axiom: "don't fix it if it ain't broke", as I do, then give it time and continue to use Sea Foam in the gas, I'd do it at at least twice the normal rate (2 oz per gallon) and give it some time to finish what it started.

If it doesn't clean up then I'd suspect the carbs first as oldman mentioned and take them off and clean them up ensuring you get all the passages accessible to compressed air.

Case in point: I just worked mine over and although the bowls were spotless, it wasn't until I got out the compressed air out did I find my smoking gun...some kind of foreign matter clogging the high speed jet on one carb which I didn't see till the air dislodged it.

HTH,
Mark

 

[Chamelion]

Re: Motor idle/starting issues

Some where the fuel system either has a fuel blockage or air leak, or the carb floats are sticking shut from the way you say it is acting. Might have a blockage in the fuel vent on the tank, or bad conector or clamps on the fuel hose. The motor should be equipted with a mercury switch, that will kill the motor if it is tilted up to far, to where the motor should be out of the water. That is a safety to keep from a overheat alarm and causing damage from that condition. Use a diffrent tank and hose to see if the they are the trouble or if it is on the motor. Could be the fuel pump needs rebuilt if the primer bulb dose not calopse and stays ready to prime. Fuel pumps will get to where they will pump enought fuel for the motor will run at idle but not at higher RPM. If the hoses, and all rubber components, are ones that are not ethenoal resitant and you use that fuel it has a tendancy to cause trouble over time. New hoses, and rebuild kits are made to handle the ethenoal fuel. The timming should be set at spec for the motor as damage, burnt pistons, can be done if set to fast. JMO
Oldman570

The same issue occurs with both of my fuel tanks, so we can pretty much rule that out. Whilst it could be the clamps (mostly zip ties from the previous owner) the only thing that changed between working fine and not was the de-carb. The primer bulb will go soft when running the motor. The problem is that it appears to completely empty itself if the motor isn't running, even if I prime it and then don't start the motor. Whilst running in idle it seems to starve itself. Giving the bulb a squeeze when it starts to show signs of cutting out solves the problem for a few moments.

I can't speak for the previous owner, but I don't touch ethanol fuel, not for any motorised device.

Yet to check the timing at higher revs, but at idle I've got it set to about TCC + 1 or 2.

The motor runs absolutely fine above idle.

I agree check the tank vent. Blow into the hose that leads to the tank pickup. If there is blockage in the vent or hose to the vent it should be apperent or clear out at that point. Set the carb screws at 1 1/4 out from a light seat. Then adjust for best idol. There may be water intrusion through the exhaust cover and baffle due to corrosion or a bad gasket which lets water into the exhaust port mixing with the fuel causing it not to start or run rough. sputter or even backfire. This happened to my 79 40 2 stroker. I replaced the cover and baffle.The baffle had corroded through. I upgraded to a 70 HP and parted most of the 40 out. The only pic I have is my ebay add and pretty sure they will not work on a 2002. But for reference I,m posting them. Exhaust cover 55157 and divider plate | eBay <EDIT> As started in the next post if it aint broke don,t fix it. The exhaust senerio is a worst case explaination of the symptoms you described and should only be looked at if the problem persists over time. Decarb will tend to remove carbon from the rings and piston domes which will tend to foul the plugs. I suggest a second set of plugs and constant cleaning of the plugs until the decarb removes all the crap inside the cylinders. This is also why I stated to check the air flow through the tank first then move on to hoses clamps fuel pump filter etc etc.

I don't think these particular motors have exhaust covers. There are certainly no bolts.

I've put a good 5 hours on the motor since the de-carb and the only other connecting piece to the puzzle is that on muffs = idles great, in the water = idles and dies.

Spark plugs are quite new and still in excellent order. No sign of being fouled at all.

If all you changed was doing a decarb and have run the engine before, which you said, then I wouldn't go looking for non-related causes.

My opinion is that the decarb knocked something loose that is floating around and you never know where it will land next, nor how long it will stay.

If you subscribe to the axiom: "don't fix it if it ain't broke", as I do, then give it time and continue to use Sea Foam in the gas, I'd do it at at least twice the normal rate (2 oz per gallon) and give it some time to finish what it started.

If it doesn't clean up then I'd suspect the carbs first as oldman mentioned and take them off and clean them up ensuring you get all the passages accessible to compressed air.

Case in point: I just worked mine over and although the bowls were spotless, it wasn't until I got out the compressed air out did I find my smoking gun...some kind of foreign matter clogging the high speed jet on one carb which I didn't see till the air dislodged it.

HTH,
Mark

 

[Silvertip]

Re: Motor idle/starting issues

Primer bulbs do not stay firm after an engine starts. Fuel is sucked through it, not forced through it. You also have idle mixture issues if the engine runs out of the water and not in it. Mixture adjustment needs to be done in the water due to the back pressure.

 

[Maxz695]

Re: Motor idle/starting issues

I agree that water pressure from the impellor has alot to do with fuel flow when running.Blockage of flow will interupt exhaust pressure needed for the fuel pump. Only other thing i can suspect would be fuel pump related or blockage in the transfer port which leads to the passage for the fuel pump.