1988 70 HP Johnson Cooling System Modification (+ Additional Work)

[NoEcm]

The Victim: 1988 70 HP Johnson. J70ELCCA




Purpose:
Water pump R&R
Inspect/clean cooling system passages
Implement OMC Service Bulletin 2276 (Cooling System Modification). Here is the Service Bulletin:



The Kit:
OMC Water Pump Kit 432955 (includes the parts necessary for the cooling systems mods):


And the instructions that came with the Water Pump Kit:

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

After taking photos from every angle so I would remember how everything goes back together, the first thing I did was work on getting the exhaust cover off. I didn't pay much attention to that rusty bolt in the lower left but I should have:


I put 6 oz of torque on that bolt and the head fell off. Crappy picture but here is the inside of the exhaust cover which also shows the broken bolt:

Outside of the broken bolt, the inside looks pretty good for a 24 year old outboard that is used exclusively in the salt.

All of the bolts came out pretty easily and I wondered if the broken one would come out just as easily? I took a pair of pliers to the broken bolt and look what came out with ease:

Looking at the head of the bolt, it looks like it was rusted through and was just ready to fall off.

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

Here's what the inside of the exhaust cover looked like:


The old tell tale elbow needed to be removed also:


After 20+ years of salt water use the elbow was frozen in there so I ended up burning it out with a propane torch:

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

Here's what it looked like after it was removed:


Chasing the threads to clean them up:


The inside of the exhaust cover after bead blasting:

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

I pre-marked the new location of the tell tale elbow before disassembly:


Taping the hole for the new elbow (1/8" Pipe thread):

 

[boobie]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

Super post !! That one should be in the Top Secret Files as it answeres a lot of questions on here.

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

The original Service Bulletin says "Grease the tips of both the drill and tap to prevent aluminum chips from entering the cooling system".

After performing the drilling and tapping myself, there would have been no way I would have tried that. Advice: take the exhaust cover off, drill, tap and then vacuum and or blow the chips out. There were way too many chips and shavings to try it per the Service Bulletin.

Next, here is the cooling passage after its been cleaned up:

It came out pretty clean.


And the tell-tale elbow in its new location:



Next, the exhaust cover all painted up:


And the Satin Black paint that I used:

At $3.88 per can at Home Depot it color and finish matches pretty well.

 

[WernerF]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

Good work!
I relocated the telltale last year on my 1989 60hp, but I didn't take off the exhaust cover. I was afraid of tearing off a bolt which I couldn't work out alone. I too was concerned about chips falling into the cooling system. So I drilled very slowly and held a vacuum cleaner at the hole while drilling. I tapped the hole in many small steps, cleaned and greased the tap in between. I think small aluminum chips won't hurt much at this part of the cooling system. They would hurt in the water pump, but here they are rinsed out through the wide passages before the thermostat opens.

Is your thermostat 24 years old as well? Then I would replace it. I've never seen a 20 year old vernatherm still working correctly, neither in an outboard, nor in a car.

What about the stronger thermostat spring and replacing the overboard indicator/restrictor? I haven't heared about these yet. What's wrong with the original ones?

 

[fishfeatures]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

Super post !! That one should be in the Top Secret Files as it answeres a lot of questions on here.

+1

have bought all the bits to do my 1990 60hp but was a bit hesitant. With these step by step instructions I feel more assured to go and attempt it.

Thanks NoEcm

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

With the Cylinder Head removed you can see where the salt penetrated the head gasket:


And where the salt leaked through the gasket onto the head:


A well worn .38 caliber cleaning brush works great for cleaning the cooling passages:

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

The old restrictor and the grommet that replaces it:


And the new hose:


And what the grommet looks like installed:



The new hose coming from the top of the block goes right through new grommet.

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

Reason for the cooling system modification?

Purely speculation on my part.

I'm guessing that the OMC engineers felt that there was enough cooling water passing through the inside of block and:
1. That more of that excess water could be bled out through this modification
2. Which would also allow more of the trapped bubbles at the top of the block to be bled out also

What do you think?

 

[WernerF]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

Maybe it's because the restrictor clogs so often?

 

[fishfeatures]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

The old restrictor and the grommet that replaces it:

Is there a need to replace the restrictor with a grommet when doing this?? if so is there a part number for it?

 

[WernerF]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

NoEcm, please compare the new water pump with the old one when it's removed. It might be possible that the new pump is stronger and all the changes (restrictor & spring) are related to this.

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

Maybe it's because the restrictor clogs so often?

Excellent thought and probably so

Is there a need to replace the restrictor with a grommet when doing this?? if so is there a part number for it?

Not sure but it came with the kit so I installed it.
No part number that I could find but I think I could find something similar at the harware store. All this grommet does is hold the indicator hose in place when the restrictor is replaced.

NoEcm, please compare the new water pump with the old one when it's removed. It might be possible that the new pump is stronger and all the changes (restrictor & spring) are related to this.

Will do


Here is a picture of the kit showing all of the contents (taken from the eBay ad that I purchased from):

 

[boobie]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

How many blades did the orginal water pump have ??

 

[roger46982]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

I have the same engine with the upgrade water pump kit but mine only came with the original spring, not the cone shape one, will this cause me any problems?

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)

How many blades did the orginal water pump have ??

No idea, the original pump was changed in 1992 and I can't remember back that far.

I have the same engine with the upgrade water pump kit but mine only came with the original spring, not the cone shape one, will this cause me any problems?

According to the instructions you use either the 15/16" ID spring or the cone shaped spring along with the new thermostat cover. You don't use both.

As you can see from the parts kit photo, the upgraded spring is Red and my original spring was not colored. What color is the spring in your kit?

Also, did the instruction in your kit reference the cone shaped spring?

 

[NoEcm]

Re: 1988 70 HP Johnson Cooling System Modification (+ Additional Work)



Head re-installed:
-Bolts torqued down to 225 inch pounds
-New head gasket
-New thermostat
-New "Red" Spring installed


How many running hours should I have before I retorque the head and exhaust cover bolts?