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Mercrusier 340 mie dies

R

RomDawg

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Dual 87 mercrusier model 340mie, q-jet carb, tbiv. Bought boat this pass winter. Has not been in service for a season. Dropped her in water and made a 140 mile power home. Prior to leaving replaced all standard tune up parts. Cap, rotor, plugs, wires, and filters also fresh fluids. Boat ran like a dream entire trip. Almost 10hrs non stop. Now to the problem. Next trip out boat ran great untill we got to fishing grounds. About a 9 mile power before setting up to troll. As I go to bring the sticks down i get to about 2k rpms from 3100 and port motor shuts down. Just shuts off. Not spit or sputter. Go to refire motor starts and dies. Refire again with throttle cracked open fires up to 1500 than just drops down to 0. Wasn't prepared for testing at that point just wanted to get back to slip. So pwr back on one. Get to slip and go to do some testing. Go to fire it up and runs for couple seconds and dies out. Have 0 issues getting this thing to start on first crank. Just won't stay running. Have 0 throttle control once it does fire up. Can push throttle all the way open and won't change rpms. Crack throttle open and crank again it goes high rpms than just dies after 2-3 secs.again no throttle control. Only way I can get it to retfire and run is to let it sit over night. Fires up next day great runs in slip for hrs. Go to fish and pwr to same spot and it does the same thing all over again. This has happened 4 times in a row ( replaced parts inbetweenfailed trips). The motor now has another set of fuel filters, replaced anti siphon valve in Port tank, replaced fuel feed line from tank to pump, rebuilt carb(float had fuel in it, thought I had figured it out with that) another set of plugs, and a coil. As I stated earlier I did the "maintenance" items before bringing the boat back to home. The last thing I had done was the fuel feed line. In my opinion this made the biggest change in motor performance I was able to pwr 25 miles before it decided to die out again. About a min before it died the rpms dropped about 400 rpms gave it more gas to get it to keep going, to keep it at 3k made my throttle sticks very uneven. But it held steady at 3k with uneven sticks.untill I brought it off pwr to come into port. Started to bring rpms down and it just shut down. also I did notice that when the rpms dropped my exhaust smelt rich and was steamy. That's probably not the correct description of exhaust but it wasn't smoke. So at this point I end up here. Any help would be greatly appreciated.
 
What are you describing as fuel feed line (from point A to point B)??

Have you determined whether is SPARK or FUEL that is the problem once the engine has run?

Filling in some of the holes in your description, I'd suspect a fuel starvation condition caused by crud in the port tank collecting on the pickup tube screen...
 
I have replaced the fuel line from tank to pump. On this last trip where it ran for 25 miles, I ran the whole time on my port tank. Both engines.star engine never missed a beat. Was trying to see if it was a tank issue. I have only tested for spark once and that was at the coil. And I had great spark.bright blue jumped spark testor.
 
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Rubber fuel lines made before the introduction of ethanol (circa 2006) will have their lining degrade with time if used with ethanol "contaminated" fuel. The lining is apparently solvent in ethanol and will pass thru 10 micron filters. Also ethanol causes deposits on the innards of the fuel system. Some of these deposits do not respond to normal "carb cleaner" products as it forms a rock hard biege colored deposit.
 
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sandkicker said:
Rubber fuel lines made before the introduction of ethanol (circa 2006) will have their lining degrade with time if used with ethanol "contaminated" fuel. The lining is apparently solvent in ethanol and will pass thru 10 micron filters. Also ethanol causes deposits on the innards of the fuel system. Some of these deposits do not respond to normal "carb cleaner" products as it forms a rock hard biege colored deposit.
Click to expand...

Yes, I totally agree. Hence the reason I replaced the line.
 
I'd still suggest you need to assess the initial factors when the engine loses RPM or dies....assuming the engine is serviceable mechanically, it needs spark and fuel.....and I'd suspect one or the other
 
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