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Motor dies at 3500 4000 rpm

H

headliner64

New member
"4.3 l mercrusier alpha 1 thun

"4.3 l mercrusier alpha 1 thunderbolt starts fine runs fine till i go to plane out at around 3500 rpm then it dies. i've already changed fuel filter, plugs,wires,cap, and rotor anybody got any ideas."
 
"What year, carb or MPI, elec.

"What year, carb or MPI, elec. or mech. fuel pump?

Check fuel vent line for a low spot for fuel to block the vent. Check the vent for spider web/nest."
 
"Vent disconnected where?

W

"Vent disconnected where?

Will it restart immediately and run like nothing happened? Did you check for fuel and spark when it dies? What is the fuel pressure when it dies?

Possibilities:

**dying fuel pump or *corroded wire connection in-line to the fuel pump; trace wires, common problem

* fuel vent blockage;

* antisiphon valve blockage

* dying fuel pump relay

* dying coil

** rusted/corroded optic sensor in dist.

** dying spark amplifier module

* higher probability

** lower probability"
 
"yeah it starts right back up

"yeah it starts right back up and acts like nothing happened , the vent is the tube coming off the tank right? we disconnected there to see if it still did it and it did . i didn't check the fuel pressure i need to buy a tester. thanks for the help i'll check all these"
 
I recently had that problem.

I recently had that problem. Timing advance wasn't working and motor would stall at high rpm. The spring weights under the distributor plate were broken.
 
Does the motor shut off when y

Does the motor shut off when you mean die? I once had a bad tach that would kill my engine around 2800 motor would shut right off. If this is the case try the tach.
 
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