OMC 4.3 cuts out when i press trim button

[Minnesota Jeff]

I have a 1989 Four Winns OMC 4.3 that i just bought. When running at any speed less than full throttle, everything works fine, but when running at full throttle, if I press the trim switch (either up or down), the motor cuts out momentarily. As soon as I release the button, it's fine... any ideas? It's pretty annoying!

Also, I found the remnants of an exhaust flapper in the bellows - no idea how long it's been burned out. I've read alot of discussions on running with and without them - comments?

Lastly, i've also noticed that sometimes at full throttle, it "sounds" like it's missing a bit, but it runs strong - could what I'm hearing as a "miss" int he engine possibly be more of the flapper or the other flapper bouncing aroudn somewhere in the exhaust? it's not constant, but occasionally at full throttle.

thanks everyone

 

[bruceb58]

Re: OMC 4.3 cuts out when i press trim button

Sounds like there is a bad ground somewhere. You are dropping the voltage to the ignition when you apply the trim.

Try measuring the voltage at the coil under these conditions and see what is happeneing.

 

[Fishstick1962]

Re: OMC 4.3 cuts out when i press trim button

I might start by looking in the control box. Maybe when the throttle is moved all the way up, the trim wires come in contact with a hard surface. Since it only happens at WOT. I'd be looking in the areas affected by moving the throttle. I.E. control box and engine linkage areas.
Hope this helps.

 

[WillyBWright]

Re: OMC 4.3 cuts out when i press trim button

How's your battery? If you're losing spark with a significant amperage draw, that would be the first place I'd look. I'd also be looking at the alternator to make sure it's charging. At full throttle, the ignition system is pulling it's hardest. Add more draw and spark could be lost.

 

[bruceb58]

Re: OMC 4.3 cuts out when i press trim button

Ignition systems do not have enough current draw for this to be the problem. It is more of a voltage drop problem due to the increase current draw of the trim motor.

I am going to add another item from my previous post. There will be a large wire that connects to where your main battery cable connects to the starter solenoid. This large wire feeds all the electrical in your boat including the trim and the ignition. If there is a resistive connection along that path, you will get a significant voltage drop to effect your ignition.

Best thing to do is to check voltages while you are operating the trim circuit.

If all checks well, it could be that your coil has aged and is not stepping up the voltage like it used to and is marginal at a lower voltage input.

 

[wavehogger]

Re: OMC 4.3 cuts out when i press trim button

This may sound too simple, but I had the same thing happening to me with my 88' Mach 1 270hp 5.7l. I changed the plugs, cap, rotor and ignition sensor, and it is totally gone. I'm betting it was the ign sensor and when you hit the trim and change voltages it may affect the performace when the sensor is old and rusty like mine was at the time.

 

[mike loya]

Re: OMC 4.3 cuts out when i press trim button

there is a service bulliten on this. I had the same problem. Unravel the wire harness with the resistor wire in it. cut off about two feet of the resistor wire.this will increase voltage to the coil.Worked for me.