Reviving a 1968 Mercury 500

[jboehm]

I have recently acquired a 1968 sport-craft c-eagle with a 1968 mercury 500. The boat has spent most of its life stored inside a garage so it is in excellent overall condition. I want to revive it, but the motor will need some updates before I attempt to get it running. The motor hasn't run in more that 26 years. I did replace the plugs and impeller about 15 years ago, but didn't start it. I am looking for advice on what steps I should take to revive the motor. So far my plan of attack is as follows:

Lube the cylinders before attempting to turn the motor by hand( done and turns freely)
Complete water pump replacement
New lower end fluid
Replace the internal wiring harness
Hope it starts and run it on a heavy fuel/oil mix.

Now for the should I list:
Replace fuel lines
Replace distributor drive belt
Lower end seal replacement

Any advice is greatly appreciated.

 

[Scott Danforth]

I would also install another new impeller. the last one has long taken a set.

 

[jboehm]

Yep, impeller came with the water pump kit. How about the fuel pump? I do have some spare fuel rebuild pump kits.

 

[jboehm]

Wiring harness in hand so I think I have all of the parts I need to begin the process. I noticed some oil coming from around the prop. This started after I shot 2 cycle oil and fogging oil in to the cylinders. Could it be the oil from the cylinders or do I have a lower unit leak? It isn't coming from any of the drain/fill plugs.

 

[Michawilden]

That will be unburned fuel dripping out of the Lower unit. Have you checked the engine for spark?

 

[jboehm]

That will be unburned fuel dripping out of the Lower unit. Have you checked the engine for spark?

I don't think it could be fuel since I haven't put any fuel to it. I am thinking it might be the oil I put in there, but the 2 stroke oil has a green tint and the leaking fluid is brown. I guess it could have mixed with other stuff as it went down the exhaust. I haven't done a spark text yet. I want to get the. New harness installed first.

 

[jimmbo]

Gear oil stinks to High Heaven. 2 stroke oils don't smell anywhere near as bad

 

[jboehm]

Gear oil stinks to High Heaven. 2 stroke oils don't smell anywhere near as bad

I checked it yesterday and the dripping oil didn't have any smell so maybe it is old 2 stroke oil.
Anyone have a description on how to remove the lower water pump base? Do I remove all of the studs running through it?

 

[jboehm]

How does the brass water tube connect to the pump? It appears there is a rubber seal install from the bottom of the upper housing. Does it press in to that? Shoudl I remove the tube from the block and install it first on to the pump or does it matter?

 

[DeepCMark58A]

No need to mess with the brass tube, it just kinda presses back into place when you reassemble the lower unit

 

[60sboater]

See if there are any related vids on YT. I found a few when I did an impeller replacement on a 1973 9.8 Mercury. You can pressure test the l/u. Dangar Marine on YT has a vid on it and many other areas of maintenance.

 

[jboehm]

Time to verify wiring. I attempted to ohm out the original harness to determine if my CDI replacement harness had all of the wires in the correct position. As far as I can tell it does. Looking at the attached diagram, since it is the most accurate appearing one for my motor, it appears the red wire to the recitifier and the red wire to the switch box are hot all of the time. It also seems the red jumper attached to the switch box shares a lug on the box. Is this correct. My CDI harness and my original harness differ in this area. On the original there were three red wires that I believe all originate from the main battery wire. One goes to the solenoid, one to the recitifier, and the other to the switch box. On the diagram it shows two, one to the solenoid and one to the switch box. Then there is a jumper from the switch box to the recitifier to pick up 12 volt power. Now, my CDI harness has an extra small black wire that seems to ohm out to come from the ground. Is it an additional ground for the solenoid?

 

[GA_Boater]

If the CDI harness is a 414-2770, the black wires are explained below from the CDI Instructions. The small black goes to the ground connection on the solenoid like the diagram above.

 

[jboehm]

Okay, black wire confirmed. The instructions say to connect the small red wire directly to the rectifier. it doesn't say anything about adding a jumper from the rectifier to the switch box, but I can see the connection in this diagram and my original had a hot connection to the switch box,

 

[jboehm]

Speaking of the CDI instructions. What is the difference between Battery type ignition and alternator driven ignition? Which one do I have? The instructions for Battery type seem to best match up with my original harness, but not exactly.

 

[GA_Boater]

All I know for sure is to see what part number the switch box is.

I think an alternator system can be started with a dead battery and a battery driven one needs a charged battery. Something like that.

 

[merc850]

The ADI system uses power generated from the stator to fire the multiple coils - the CDI system like yours uses battery power to fire the (1) coil; from 5 to 19 volts.

 

[jboehm]

The ADI system uses power generated from the stator to fire the multiple coils - the CDI system like yours uses battery power to fire the (1) coil; from 5 to 19 volts.

Am I correct that the rectifier and switch box will always have battery power if the battery is hooked up? The CDI instructions say to run the small red wire first to the rectifier then jumper it over to the switch box. I wired mine like the diagram, first to the switch box then jumper it to the rectifier. If the small red wire is always hot then it shouldn't matter.

 

[jboehm]

After messing with this for almost a year I finally found time to start it. IT RAN!... for a minute. After getting it to start and run on the muffs I set it up to run in my test barrel. When I went to pump the bulb it wouldn't get hard and I found gas running out of the top carb. I did try to start it , but it wouldn't fire. Should it have at least run some with the carb leaking? I am trying to determine if there is now another problem besides the carb. As for the carb, Does it sound like a stuck float?