[zugzug]

There are times, not always that when I am trying to use the trim tabs it almost shuts my motor down. I get the same electrical power loss at times when I am just idling around and not at any medium/high RPM range. Kind of sounds like the engine is cutting out and about to die until I bring the RPM’s up. If I am running full out or close I do not get any hesitation when using my trim tabs or any other electrical device. The radio above ¾ volume will also cut out unless it is turned down just a hair. Anyone have the same experience or have any advice? I have a 7.4, Z240 Talari and have removed the tachometer wire from the coil since someone said that sometimes caused electrical issues but that did nothing. Feel it may be a grounding issue but I have checked all the cabling from the duel battery setup to the battery selector and do not see any loose or corroded cables. Any suggestions are welcome!

[elrack]

I had a similar issue on a past boat. Using trim tabs at idle would trip the thermal breaker mounted on the motor. It was a loose ground, if I remember right at the engine block.

[zugzug]

Thanks elrack! I will check that out. Mine hasn't tripped any breakers at this point but all it but kills my engine.

[Hudson River Steve]

What you are experiencing is most likely caused by a loss of voltage. When you use the trim tabs you are pulling a decent amount of current to run the pump and solenoids. If you have a poor connection on either the B+ or the B- wires it will cause a voltage drop. If the voltage that your 7.4MPI sees is low enough the computer will turn off. The same can be said for your stereo, if it pulls enough current and has a high resistance connection it will brown out and turn off.
As elrack suggests it is probably due to a loose or corroded ground on the engine block since you said that you already checked the B+ wires from the battery to the selector switch. The 7.4MPI has one or two large grounds that are connected to studs on the rear of the engine. If I recall correctly they are combination bolts/studs that hold the bell housing onto the block. I would remove the nuts that hold these large gauge black wires and wire brush both the stud and the crimped connection on the black wires until both are shinny clean. You may also want to check/clean the heavy red wires connected to the engine starter solenoid including the fuse, circuit breaker and large engine connector.

[zugzug]

Thanks Hudson River Steve! That all makes since even with me running a carburetor 7.4 not MPI, but still voltage is voltage computer or not. I will check all my main leads again and give it a try. Any other suggestions from members is welcome since I like to exhaust all opportunities.

[1996 Mariah Z252]

Originally Posted by zugzug

There are times, not always that when I am trying to use the trim tabs it almost shuts my motor down. I get the same electrical power loss at times when I am just idling around and not at any medium/high RPM range. Kind of sounds like the engine is cutting out and about to die until I bring the RPM’s up. If I am running full out or close I do not get any hesitation when using my trim tabs or any other electrical device. The radio above ¾ volume will also cut out unless it is turned down just a hair. Anyone have the same experience or have any advice? I have a 7.4, Z240 Talari and have removed the tachometer wire from the coil since someone said that sometimes caused electrical issues but that did nothing. Feel it may be a grounding issue but I have checked all the cabling from the duel battery setup to the battery selector and do not see any loose or corroded cables. Any suggestions are welcome!

See if the battery cables are corroded or if your alternator is bad.

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