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Old 07-25-2013, 12:56 AM   #1
Join Date: Jul 2013
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Default Trouble with my 4.3 lx bogging but not fuel

I have a maxum 2000 sr2 with a 4.3 lx mercruiser that I just purchased. The boat had sat outside without cover for two years prior to my purchase. I replaced the fuel and separator, sprayed carb cleaner and put sea foam in gas. Boat starts right up and seems to run amazing. The first time I put the boat on the lake I noticed it seem to take about 3 minutes of full throttle to get on plane. All the gauges showed normal perameters. After running for roughly 10 minutes I stopped engine and sat for around an hour. After about 3 minutes of full throttle the boat started bogging down from 4300 rpm to 2000 or less. I stopped the boat and could rev the motor in neutral to 5000 rpm no issues. Upon restarting the boat would run for about 10 seconds at a high rpm then bog down again. This has happened on 2 separate (only) trips out. Both times I had to idle the boat in gear back to marina. I cleaned carbs between trips and made sure fuel lines weren't breaking down (weren't). Not sure where to look but did notice when problem was happening and I used the electric motor to drop or lift stern drive or turn light switches it seemed to have A immediate effect on motor. Also pulled battery cables while boat was idling and engine continued to run but for some reason now anchor and nav lights aren't working. Should I look towards the coil or the carbs?

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Old 07-25-2013, 01:51 AM   #2
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Join Date: Nov 2010
Location: Massapequa, New York, United States
Posts: 762

sounds like water in the fuel, as you slosh it around under way, the water on the bottom mixes with the fuel on top, and shows when the engine is under load and need the fuel for power. Idle is just the engine free wheeling, and can handle water and not effect it.

Rig a temporary tank up and try it.

As far as your electrical issues, I suspect you blew the fuses when you disconnect the batter while running, as alternator tend to spike when that happens.

Electrical engine problems are rarely intermittent.

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Old 07-25-2013, 08:48 AM   #3
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Location: netherlands
Posts: 158

yep, sounds like water in the fuel. remove the fuelfilter and empty it. on top there will be colourless fluid (water). it's possible you can even see some rust on the inside. replace it with a new one.
if youre problem is solved this doesnt mean it will stay away.
the mixture in youre tank is the big problem.
since water is more heavy than gas it sits on the bottom. (you can have it sucked out but if there is '95 ron in the tank the whole mixture must come out.
'95 mixes with water, '98 doesnt.
have condenswater issues every year.
only thing that helps is emptying the tank and fuel filter (don't forget to clean the carb)
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Old 07-25-2013, 10:24 AM   #4
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I thought of that first actually so I did replace the water separator already and didn't notice any discoloration. Also boat had less than gal of fuel in it and I put some revitalize as well as 15 gal of fresh fuel and seafoam. Why would there be no issues while revving in neutral while the problem is happening but automatically have issues when in gear and under load. Also have no torque to speak of
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Old 07-25-2013, 10:26 AM   #5
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Also when I rig a temp tank to try to isolate, what should I use as a pump
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Old 07-25-2013, 11:36 AM   #6
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Disconnect fuel line from built in tank and connect it to the temp tank, this will still use the existing fuel pump. Did you drain the tank before filling? Any water in the tank won't mix with gas and with the tank that low condensation will occur over 2 years. It does't that much power for an engine to rev with no load hence in netural no issues.

If running on temp tank doesn't fix the problem it's probably time to rebuild the carb. Spraying all the carb cleaner you want wont resolve years of gum sitting in tiny passages.

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