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Engine problem with load 1994 4.3 L

9

94Wellcraft

New member
Need some help here...I have a mercruiser '94 alpha1 4.3 LX with Thunderbolt IV ignition system. Starting last year I have had engine trouble while in the water. I had start up problems earlier, but found that my timing was off by quite a bit. Got that fixed and engine started great with muffs on in the driveway. Engine ran fine over 5000 RPM's in driveway. Once launched, at idle evrything was fine, even started great. With a little throttle around 2000 RPM's, backfiring a lot, engine smoothed out with a little more throttle. Got engine up to 4200 RPM's and 32 MPH, then RPM's dropped to 3000 and the boat was moving around 10 MPH. Engine quit, hard to start, finally got it started, but would not stay running, and occasionlly would surge. I have checked cap and rotor, plugs, fuel pump pressure, fuel lines, siphoned out all the gas and replaced. Put some sea foam and octan boost in. A this point I am going to pull the carb.- it is a Weber 4 bbl. My uncle is a mechanic, so he will be assisting and I have subscribed to SELOC online.
P.S. On a side note, thanks to all who stop for someone broke down on the water, and to the two boats that passed me while I swam/pulled boat in while my wife used an oar to stay off the rocks, well I hope someone stops for you if you need it!
 
Re: Engine problem with load

Did you check for spark when it would not start? Does the accellerator pump provide two good squirts of fuel when the throttle is operated? What did the optic trigger under the rotor look like? If it is rusted that can contribute to not running right. Octane boost will foul the spark plugs. A carb rebuild can't hurt it. Good luck.
 
Re: Engine problem with load

94Wellcraft said:
Need some help here...I have a mercruiser '94 alpha1 4.3 LX with Thunderbolt IV ignition system. Starting last year I have had engine trouble while in the water. I had start up problems earlier, but found that my timing was off by quite a bit. Got that fixed and engine started great with muffs on in the driveway. Engine ran fine over 5000 RPM's in driveway. Once launched, at idle evrything was fine, even started great. With a little throttle around 2000 RPM's, backfiring a lot, engine smoothed out with a little more throttle. Got engine up to 4200 RPM's and 32 MPH, then RPM's dropped to 3000 and the boat was moving around 10 MPH. Engine quit, hard to start, finally got it started, but would not stay running, and occasionlly would surge. I have checked cap and rotor, plugs, fuel pump pressure, fuel lines, siphoned out all the gas and replaced. Put some sea foam and octan boost in. A this point I am going to pull the carb.- it is a Weber 4 bbl. My uncle is a mechanic, so he will be assisting and I have subscribed to SELOC online.
P.S. On a side note, thanks to all who stop for someone broke down on the water, and to the two boats that passed me while I swam/pulled boat in while my wife used an oar to stay off the rocks, well I hope someone stops for you if you need it!
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with the engine surging best open up the carb and clean ..

you started this when first trying out engine , with the old fuel and not checking fuel condition ? If so this is most likely the carb dirty..
 
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