Tune up suggestions.

[MK3MA70]

Hey guys, looking to do a tune up on my Johnson 120 V4. Wondering if anyone had any suggestions or reviews on plugs, wires, carb kits. Also, should I worry about replacing the coil packs? This is my first outboard so any advice would be great!

 

[metriccrescentwrench]

Re: Tune up suggestions.

First step is to get a factory service manual if you don't already have one. Not one of the generic aftermarket ones but the real OMC factory manual. They're usually available on ebay.

What year is your engine? Is there anything wrong with the way it runs, or are you just looking to do PM?

One thing you might want to do is a compression check to determine the overall health of the engine.

Don't go replacing coils unless you have a reason to do so. The plug wires are pretty much indestructible since they're wire core. The only reason to replace them would be physical damage. As for the plugs, you can go to shop2.evinrude.com and drill down to your engine and the plug type will be listed.

 

[MK3MA70]

Re: Tune up suggestions.

I actually just ordered a manual today. Hopefully I will have it before next weekend. According to the Johnson site, its a 1989. When I took it out for a test run, it ran pretty strong, sounded good. Only thing is it would sputter a bit probably due to bad/lack of fuel or both. Previous owner said that the boat had been sitting for about 6 months with no fuel stabilizer. Other than that, it exceeded my expectations. I was considering a compression test although I have a question regarding the jumper wire rigging. Basically, from the positive side of the battery terminal directly to the stater solenoid or to the stater itself? My goal is to make sure that I know the motor is lake ready.

 

[Chris1956]

Re: Tune up suggestions.

Normally all you need to do is monitor compression, do PM on waterpump, grease zerks and steering rod and change gear oil once per year. Change spark plugs every couple of years, if you feel like it.

 

[metriccrescentwrench]

Re: Tune up suggestions.

... I have a question regarding the jumper wire rigging. Basically, from the positive side of the battery terminal directly to the stater solenoid or to the stater itself?

That's normal, from the battery to the solenoid.

 

[archcycle]

Re: Tune up suggestions.

You want the small terminal nearest to the battery positive for the compression test. Buy some alligator clip jumper wires at radio shack and ground all 4 plug wires while you're doing this.

Check out the decarbing instructions in the top secret files-
http://forums.iboats.com/showthread.php?t=299680

You'll want to change the water pump impeller as soon as you get your manual. Be very careful not to disturb the shift rod's orientation when you drop the lower unit or else it won't shift correctly and you'll have to drop it again and measure/reset the rod. That's something you'll want to avoid.

Gear oil in the lower unit needs to be changed yearly so you might as well. Empty the gear oil from the lower unit and replace with new marine gear oil. You'll need a gear oil pump for this which will probably be found next to the gear oil at the store. You remove the upper and lower drain screws, let the old oil drain (if it's milky white then you have water getting in there and will need to rebuild it at some point sooner than later), and then pump new gear oil in from the bottom hole until it comes out the top one and close it up.

You'll also want to top off the tilt/trim fluid. Get a tube of it and run the motor all the way up, put it on the bracket, and remove the giant round flathead bolt on the reservoir. It helps to have the boat/trailer as level as possible. Fill it up, run it up and down, and try filling it again. Even if it's full this is good stuff to have on hand and it's only a few dollars. Your TnT is self bleeding you just run it up and down a few times and it takes care of it.

 

[MK3MA70]

Re: Tune up suggestions.

You want the small terminal nearest to the battery positive for the compression test.

According to the wiring diagram found in the sticky notes, you are referring to 3 and 6, and that disables the ignition? Also, just wanting to confirm, it says to have the ignition in the running position? Regaurding the fuel line, I still have the VRO pump. I can just disconnect the fuel line going into the pump? And it wont hurt the VRO pump?

 

[weekendfisher]

Re: Tune up suggestions.

You can disconnect the VRO line to do the compression test so long as you don't run the motor without it.
The VRO pump will only really fail if it has been running without oil for a while if the diaphragm is allowed to dry out.
Cheers

 

[archcycle]

Re: Tune up suggestions.

You want the small terminal nearest to the battery positive for the compression test.

According to the wiring diagram found in the sticky notes, you are referring to 3 and 6, and that disables the ignition? Also, just wanting to confirm, it says to have the ignition in the running position? Regaurding the fuel line, I still have the VRO pump. I can just disconnect the fuel line going into the pump? And it wont hurt the VRO pump?

You can disable the ignition so it doesn't spark or you can just pull the boots off the spark plugs and use 4 alligator clip jumper wires to ground them to the block. The idea is both to not start the motor and to have somewhere for the current to go since it's not going into the plug. As long as I've got the spark taken care of I don't worry about what the fuel is doing.

The positive goes in one side of the solenoid from the battery to the Large +12v pole, the next one over is the Small +12v from the keyswitch to engage the starter, the next one is the kill switch override, and the next one is the Large positive going out to the starter motor. Jump the Large +12v from in from the battery to the Small +12v starter switch pole. Alligator clip jumper wires from radio shack are useful for this sort of thing. If you don't feel like using a jumper wire on the starter solenoid just have someone turn the key for you.

As long as you've got the kill switch pulled (if you've got one) or else have the spark plug wires grounded then it won't try to start on you.

 

[Chris1956]

Re: Tune up suggestions.

Don't disconect the VRO oil line, when doing the compression test. It is unnecessary and potentially harmful.

If you do you will need to bleed the oil line and run a tank of premix to make sure the oil injection is working.

It is also not necessary to disconnect the gasoline line.

Jumper the solenoid primary (connect the small terminal with the yellow/red wire to the large red cable) to crank the motor, with the ign key off and do the test.

 

[MK3MA70]

Re: Tune up suggestions.

Awesome! Guys, thank you for all the great info. I really apprecaite you taking the time to help me out. I'm going to try everything this weekend and hopefully it all works out! Thanks again!

 

[toddschubert]

Re: Tune up suggestions.

Don't use a Auto Zone loaner compression tester. I have had them give very low readings and two others on this site had same problem. Try to find one from marine dealer if you don't have one.
Make sure you run test while on water muffs. Even a few seconds of running a dry water pump can damage impeller