I'm trying to bench test a 2.5l and need some help with wiring.

[Jpott]

hello,

I have a sportjet motor 2.5l v6 with the 8pin merc plug on it. Id like to test this on a stand before I drop it in the boat. I have it bolted down to a cart now so it shouldn't be too bad. I can hook water up to the baseplate, and the battery can be tied in as well.

My question is: What do I need todo with the 8pin connector to run a switch line/or maintain don't contact to fake the start/run position. I can't use the existing harness because it is cable tied in the boat. I was going to get a male 8 pin connector and wire up the test switches.

Anyone have a true pinout or schematic on how this works?

[David - WI]

Basic wiring (I think)...
https://www.biggerhammer.net/mercury...200_wiring.jpg

[skialot2]

To make the motor run on a stand you need to connect 6 wires from the harness to the switch

Red = hot
purple = switched hot
Black = Magneto
Black/yellow stripe = magneto stop
Yellow/red stripe = starter solenoid
Yellow/black stripe = Choke

[Jpott]

Yes!

Thank you. The switch continuity diagram is what i have been missing. I've got it from here. Thanks!

[25two.stroke]

If its not efi then its way more simple than that. Just jump the starter and it will run. To kill jump the black+yellow to ground off the switchbox or choke the carbs.

If its efi you have to power up the purple wire. Regardless its easier to forget about the plug and do any temporary wiring you need to do on the motor itself.

[Jpott]

If its not efi then its way more simple than that. Just jump the starter and it will run. To kill jump the black+yellow to ground off the switchbox or choke the carbs.

If its efi you have to power up the purple wire. Regardless its easier to forget about the plug and do any temporary wiring you need to do on the motor itself.

What!?! No Way... Mine is an old school carbed model so this should be super simple... I thought for sure that there is a power feed to the electronics through the keyswitch. So what keeps the battery from being drained from the switchboxes/ecu? or is the power to those boxes generated from the magneto once it starts spinning?

[25two.stroke]

Generated by the stator when the flywheel is spinning. The ecu on efi motors can draw some power when the motor is off but the purple wire is powered up...but on a carb motor the engine is "ON" or in the "run state" when no harness is plugged in. If you crank it then it will start. You dont need to power anything up to make the engine "turn on."

When you plug a key harness into it and the key is in the "OFF" position it grounds out those black+yellow wires; effectively shorting out the ignition system to keep it from running if it were to crank. But again, no power is needed or consumed.

You can see this if you study that first picture of the key switch continuity in the different key positions. Also why these key switched can cause havoc when they fail or start to fail...they have both positive and negative running through them. Unlike a car or inboard key switch which typically only switches positive.

[skialot2]

What!?! No Way... Mine is an old school carbed model so this should be super simple... I thought for sure that there is a power feed to the electronics through the keyswitch. So what keeps the battery from being drained from the switchboxes/ecu? or is the power to those boxes generated from the magneto once it starts spinning?

Yes. 25two.stroke is correct. The spark is generated by the stator. The key switch shorts it out. If you pop the 8 pin harness plug. You can jump the starter and a carb motor will start up. To shut it off, plug the harness back in. On an EFI you just need to jump the purple switched hot to give the EFI power.

[Aaronhl]

Have a 3 liter efi that I want to check compression on cold, I plugged the 8 pin control in and didnt spin after turning the key... What other wires do I need to connect?

[OnPad]

How about the neutral safety?

[Aaronhl]

How about the neutral safety?

No I don’t think so I have the engine on a stand in the garage with the EFI piece off the front, it’s a 2003 EFI non optimax…so many wires on this one…used a set of controls and they are in neutral, I’ve jumped the solenoid on my older EFI powerhead wondering if I can do the same with this one but easier with the key switch

[Aaronhl]

I dont need the injectors to squirt only want the crank to spin, seems like something electronic is not letting me do that

[skialot2]

I dont need the injectors to squirt only want the crank to spin, seems like something electronic is not letting me do that

Use a test light to check if you are getting power to the solenoid when you turn the key. The easiest way to do a compression check is to use a starter test button to jump the starter solenoid and crank the motor.

[Aaronhl]

Use a test light to check if you are getting power to the solenoid when you turn the key. The easiest way to do a compression check is to use a starter test button to jump the starter solenoid and crank the motor.

Well I checked the voltage and nothing on the start post of the solenoid when I trun the key, the issue is I cant find a factory service manual for this engine as it's not a mid 90s 3.0 EFI nor a Optimax, it's an plenum efi with the motorola box on the side... Wish I had a wiring diagram because the "starter" lug on the solenoid is actually grounded

Cant even "jump" the solenoid with a screw driver, voltage doesnt carry over the second lug

[OnPad]

Just going by memory on older stuff, but the post on the starter body is hot, and goes to the large post on the start solenoid, the positive battery cable goes to the other large post on start solenoid The battery ground would be hooked to a mounting bolt on the starter. The yellow with red or orange stripe wire, is what activates the solenoid, it also runs through the neutral safety up at the shifter. Probably goes to the ignition switch also. This is the wire that you jump power to at the start solenoid to bypass the ignition and neutral safety.