4.3 GXi stumbles, no power, won't take off

Jutgin

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Jul 22, 2017
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Well after a dozen outings today it just wouldn't go, but sometimes it would just take off after a couple hundred yards of barely going and just fly like nothing was wrong. In neutral it revs up strong. Put in gear and barely goes, struggling.
I don't know anything about boats, what can I check out?
Thank you
 

alldodge

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Howdy

Lack of fuel is my first thought. When was the last time the fuel filter was changed?
 

Jutgin

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Howdy

Lack of fuel is my first thought. When was the last time the fuel filter was changed?

Yes sir I want to agree with that, the strange thing though is when it does this I can throw it in nuetral and rev it up high nice and strong. It's only under load does it bog down. Just bought this boat in the spring so not sure about the fuel filter but changing it as soon as I can buy one. Thanks for the reply
 

alldodge

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A motor without a load on it uses next to no gas to rev high, maybe 1/8 ounce. Under load the same motor will use pint just getting on plane

Dump the contents of the fuel filter into a baggie and see if you see only clean gas. Refill the new filter with clean gas before installing, and apply a small bit of oil on the seal prior to install
 

Jutgin

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Just changed the filter, clean looking fuel was in it best I could tell dumping into a plastic bag. Changed plugs and wires. Headed out to test after the rain stops.
I noticed the small hose going to the speedometer thing was pinched, fixed that but probably not related?
Also I noticed yesterday the RPM needle randomly jumps way up for no reason. The motor doesn't actually go up, just the needle. Do you know if that is a sensor and where it is?
 

alldodge

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The tach gets pulses from the distributor, with it jumping around it could be loose connection or gauge going bad. The tach can cause the engine to miss or even die if it shorts inside. If you ever have that kind of thing show up then disconnect the wire going to it and see if it clears up.

With filter being clean and clear then next step would be to check fuel pressure at the throttle body
 

Jutgin

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The tach gets pulses from the distributor, with it jumping around it could be loose connection or gauge going bad. The tach can cause the engine to miss or even die if it shorts inside. If you ever have that kind of thing show up then disconnect the wire going to it and see if it clears up.

With filter being clean and clear then next step would be to check fuel pressure at the throttle body

Appreciate the help!
How do I check the pressure at the TB?
I contemplated replacing the distributor and coil.
 

alldodge

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Will need an adapter like Merc's 91-806901 and place it inline

TBI adapter 91-806901.jpg
 

Jutgin

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Jul 22, 2017
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Well I'm happy to report a little tune up and she runs like a scolded dog. Filter, plugs, wires, cap and rotor
 
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