This coming out of 1975 Johnson 115 lower unit.

[gilera]

I decided I'd get prepared and change the fluid in the lower unit of my motor while I work on troubleshooting the electrics. I have only owned the motor for about 1 month and not had it running yet but overall it is in good condition. When I undid the plug this is what came out. It was thick and sludgy. As I understand, these have either special OMC oil which is often replaced ATF. It does smell like ATF but usually that is red. Is this a sign of water ingress? If so what is the course of action? Do I need to replace some seals? Is it likely to have permanently affected the internals? These lower units are not compatible with other models so not easy for me to swap for another one. The prop spins around freely.

 

[racerone]

No special oil required in those.------It is not an electric shift unit.-----Pressure test this gearcase to find leaks.-----Do a compression test before spending any money on this motor.----What electrical issues are you looking at ?

 

[tphoyt]

That could be just very old oil
As Racerone says a pressure test is needed.

 

[gilera]

Thanks i'll do in that order. Compression test then pressure test on lower unit. I got told by previous owner that compression was 115 across all cylinders but won't take their word for it. I have no spark. I made a DVA tester - stator resistance (624ohms) and DVA (260V) ok although stator shows physical signs of age. Timing base ohms a little low across both pairs of sensor wires (8ohms, 8.2ohms should be 10-20ohms) but my testing battery died yesterday so couldn't do the DVA test. It was spinning the motor at good speed prior to dying though. My homemade DVA tester has a diode in it so won't be able to measure less than 0.7V but will see what I can get. I bought a new battery today and will charge it up fully and continue to test. I had the flywheel off and looks like one of the sensors on the timing base has been replaced in the past. Coils resistance ok despite cracks in all of them. At this point i'm thinking timing base or power pack.

 

[gilera]

I have all electrics off a 1980 Johnson 85 which are in good shape with CDI timing base that looks pretty good and was thinking of doing a transplant of the whole ignition system and making brackets for the coils and power packs. Problem I came across was that the bearing carrier at the top of the crank seems a different shape between these two motors. There is an angled shoulder on the later model which gives clearance. It means the timing base from that motor binds on the top of the older motor and doesn't move freely. I tried to get the bearing carrier off the 1980 model thinking that I could swap that too but it seems stuck on. If I go down this path I might start a new thread because I may need some advice along the way.

 

[McGR]

The '75 & '80 V4 motors certainly are similar in many ways, but they are also quite different too. Ignition system, lower unit and displacement are all different from '75 to '80.

I had a '76 '85hp with "cracked" coils. I think on those type coils the potting cases crack but not so much the actual potted coils. I coated my cracked coil cases potting epoxy. I ran them for several years after this without a problem. The cracking earlier OMC coils is a different story, where replacement is the only option.

 

[gilera]

The '75 & '80 V4 motors certainly are similar in many ways, but they are also quite different too. Ignition system, lower unit and displacement are all different from '75 to '80.

I had a '76 '85hp with "cracked" coils. I think on those type coils the potting cases crack but not so much the actual potted coils. I coated my cracked coil cases potting epoxy. I ran them for several years after this without a problem. The cracking earlier OMC coils is a different story, where replacement is the only option.

Good to know thanks.

Yes in regards to the lower unit, I believe that pattern is the same but the later 1980 model has the shift rod setup differently. To use later model lower units would require intake manifold also from later model. This was another idea I was considering but haven't got the carbs off yet to check whether later intake would fit - this would also mean airbox, primer solenoid, fuel pump from later model.

 

[gilera]

With my new battery I was able to get a weak yellow spark across the spark tester but only with the plugs out and nothing like strong enough to jump a 7/16 gap.

 

[racerone]

Take starter apart for inspection and ohm check on armature.---Do not rush out and buy a new starter !!------Check battery cables.-----Slow cranking means you have weak spark.

 

[gilera]

I have done all this. Replaced connectors on cables and then even tried cables from the other motor. Cleaned all earths on the motor. The starter that came on the motor had a cracked magnet and so i replaced with a good used one. The motor is cranking over nice and fast now with my new 100ah battery. My old battery was definitely part of the issue when troubleshooting. I was getting a voltage drop to about 5v while cranking after cranking it a few times. The previous owner had reported weak spark and id say he was resposible for the damage to the previous starter. I feel the problem lies in the ignition system somehwere now.

 

[gilera]

I understand this unit is not an electric shift but a hydro mechanical shift.
The original factory manual calls for OMC Sea-Lube premium blend gearcase lube. It says that if this is not available to use Dexron transmission fluid.

My 2 easiest options are:
Marine gear oil synthetic 75W90 or
Dexron III ATF which I have already.

Is there a preference for the Marine gear oil at all or will both work equally well?

 

[racerone]

Use----HI-VIS----In this gearcase.---Available at any Evinrude / Johnson / BRP boat shop if you can find one.

 

[gilera]

The closest BRP dealership is over an hour away. I rang them and they said Hi Vis has been replaced in their catalog by XPS Gear lube. The guy said that Hi Vis was 90W. I have a Merc dealer just down the road though. Would their Quicksilver Premium Gear Lube 80W90 work?

 

[McGR]

The Quicksilver 80W90 should work fine on the hydro/mechanical lower units. The earlier service info called for a lighter weight oil but then they changed the recommendation to normal gear oil. Any good quality 90W or 80W90 lower unit gear oil should be OK.

 

[racerone]

Yes it is a near match , so visit the dealer near you.