electrical rig/setup to operate 1984 Johnson V6 on stand (not on boat)

Ok experienced outboard techs. Is there an temporary-like ELECTRICAL HARNESS available for use on an engine that is off the boat and hanging on a stand? Or is this something I would need to Jerry-rig. I have my 1984 Johnson GT 150 off the boat (therefore unhooked from all controls) and would like to start it, and operate the trim/tilt as well, while it is on a stand. I can run mixed fuel/oil line from temp tank, and hook battery cables in however is required, but sure could use some help figuring out if a simple electrical harness is made and sold for this purpose. Thanks. Jerry

Here's where understanding the engine's electrical system comes in very handy.

What you probably have not realized is that with the big red plug that the boat harness attaches to UNPLUGGED, the engine will start and run just fine.
All you have to do is jump the starter solenoid to actually crank it, and it will fire right up.

But....you cannot shut it down. No harness, no key switch to kill it.

So here is what I would do....

Locate the terminal strip on the side of the motor where multiple wiring connections are made.
Find the screw terminal with the black/yellow wire attached. Make up a wire to attach to the same screw that the black/yellow wire is on.
Now, if the engine is running, shorting that wire to the engine block (ground) will kill the motor.
That wire will give you a good shock if you touch the bare end while running.

Secondly, buy an inexpensive remote starter switch at any auto parts store. Connect one lead of the switch to the starter solenoid BIG terminal that the positive battery cable attaches to. Connect the other lead to the small terminal on the side of the solenoid that has a yellow/red wire on it.
When you press the remote start switch button, the engine will crank.
Be careful, there are two small side terminals...one is yellow/red, the other is black (ground). Be sure you are not on the ground terminal.

That leaves the choking function. Since you have a primer solenoid, simply rotate the red lever on the primer solenoid to manual position, start engine and as it warms, rotate the red lever back to run position.

To kill engine, touch black jumper wire to ground. Be careful with the throttle lever....make sure it is in a controlled, known position (idle) before you try this.

Alternatively, go to a boat junkyard. There is probably an engine there that has had the cables cut when it was removed.
Find the cut end of a boat harness side...big red plug....and skin back the outer insulation. Attach the various wires to a JE keyswitch.
Plug that rig into your engine big red plug, and use the key right there at the engine.

To add to what dasel just said: Make sure you use battery cables to connect motor to battery (tight bolt-on connections). Do not use jumper cables (clip-on connections). Loose connections can cost you in serious charging system damage.

fdrgator said:

To add to what dasel just said: Make sure you use battery cables to connect motor to battery (tight bolt-on connections). Do not use jumper cables (clip-on connections). Loose connections can cost you in serious charging system damage.

Click to expand...

Thanks. I get it (Be careful). You have been a huge help, very clear and much-appreciated. Drywall-taper.

OK engine professors. Now I am wondering if my '84 GT 150 is totally-ruined, including the crank (which I suspect adds considerable cost to a rebuild). Two years ago the engine was checked to have 85-90 lbs compression across all cylinders. On a little outing with grandchildren this summer though the engine's VRO oil supply line (unknowingly) was later discovered to have developed a crack just-below the VRO pump, which undiscovered of course caused the engine to start seizing up the last mile of distance on our way back to the boat-ramp (we limped in the last mile, letting it idle 2-3 minutes, then would get the boat back up on plane approx 15 seconds though at 3500 rpms the engine would like stall again, or begin seizing again, forcing us back to idle speed. This repeated maybe 3-4 times until we had our boat back to the dock.
(At the time I suspected the problem to be a fuel related,and dropped it off at my mechanic's shop). So inspection thru the sparkplug holes indicated atleast light scoring, and compression to be 75-80 lbs on 5 cylinders with the middle cyl starboard side being 65 lbs. Did not pull the heads off and instead I chose to take the boat home. My cousin says he thinks that it is likely the "crankshaft" could be damaged some too. So thinking the engine is a total ruin, I took it off the transom anticipating replacing it with another comparable used, but good, GT 150. On the engine stand I replaced the damaged oil supply hose, and amazingly, with muffs on the engine seems to start up well and run well at idle speed on on the engine-stand. Questions: (#1)Wondering about if all year-model GT 150's were manufactured with the same prop-shaft horsepower as the '84 GT 150, Model J150STLCRD model that I have??? The reason I ask this question is that as I recall, in all '84 OMC literature,this particular GT150's horsepower was listed as "UNRATED". Question #2: I have been told a good professional complete rebuild of the engine including crankshaft could cost upwards of $3000 +/- . Should this necessarily include any head resurfacing as well, as is done with automobile engines?? Question #3: So with honing cylinders out .030", etc and complete rebuild, should I end up with pretty much the same power as my original '84 J150STLCRD had ?? Question #4: For $1500 I can buy an '89 Tracker GT 150 professionally-tested to have 98-100 lbs compression on all 6 cylinders. Maybe that's the most sensible route to go for an engine for my '83 Champ 168 Super V. ( I am just hoping to be able to run the original 24 Raker and get the kind of bow-lift I had with the brand-new '84 GT150 when it was new.) If the '89 engine might produce those results then I guess it might make economical sense to save my money and hang that '89 GT 150 on my champ. What do you experts think, is the '89 Tracker GT 150 engine going to be equal to the '84 model J150 STLCRD ? Thank you.