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Engine bogging 1996 5.7

L

looseplay

Member
Hi, looking for any other suggestions. I have a 1996 5.7 mercruiser. The engine starts fine and runs fine for about 30- 40 minutes at 3500-4500 rpm's. All of a sudden engine looses rpm's below 3000. Will continue to do fine at 2500 rpm's. Just took in to mech., found gas in oil, replaced, told me this could be from me flooding out the engine which I had done previously when problem starts. Fuel ok, fuel pump ok, cleaned filters and replaced fuel water seperator. Mech ran at 2500 rpm's for 40 minutes no problems. I took boat out yesterday and ran great for about 40 minutes, than same problems. Just looking for anything before I take back to mech. Thanks
 
Re: Engine bogging

Try running it using a outboard gas tank connected at the fuel pump.Sounds like a fuel delivery issue from a clogged fuel line(ethanol problem?) or a anti-syphon valve(1st fitting on the gas tank) jamming up.
 
Re: Engine bogging

if after trying what BT suggests and you still have the problem.

Then consider this if the fuel pump on a carbed motor gives more then 4-7 psi then you are overpowering the float needle. Check the fuel pump psi.

Good psi on the pump then your carb needs a rebuild.

But may i give some advice on how to run a carbed motor?

Pump throttle in neutral 2-3 times leave down 1/4 of the way crank motor, should idle 1000-1200. Let warm up till choke opens you will see the revs go up and the motor will sound diff.

Ok back off the throttle to neutral.

Idle should be 600-700 no more.

Ok motor warm, slowly take off and go where your going at the throttle where you want it, suggestion from me, 3/4 wot.

When you get to where you want to get slowly pull throttle back, your in neutral leave motor idle 3-4 minutes at least. then shut down the motor.

Ok want to start back up in neutral try cranking it in .

3 second crank tops. Don't start, pump throttle as cold motor.

But the motor should start if off for 1 hour or less.

Alway's leave motor warm up till choke kicks in, and when shutting down after running leave motor idle at least 3-4 minutes.
 
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Re: Engine bogging

Thank you for the advise, I will try running on outboard tank and see how it goes, will let you know. Chiefalen, thank you for advise on running the carbed motor, very new to the boating world.
 
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