Johnson 9.5 Coolant Prob.

[Usmctanker]

I have a 68 johnson 9.5 and there isn't anything coming out of the collant hole when I tested the motor. I pulled the thermostat and it was so rusted I bet it was the original from 1968. I ran it without that and still nothing so I ordered an impeller. Could anyone offer any advice as to how to change it out before i go home today and start tearing into the lower end of my motor?

 

[bassboy1]

The impeller is a very simple fix. You have to drop the lower unit. This is achieved by removing the 4 lower unit screws. Then, the lower the gearcase 3/4 of an inch or so to expose the shift rod connecter (you may have to put it in forward or reverse after you start to drop it, to align the connector with the slot). Remove the bolt with a 7/16 nut driver. Now, it should drop free. Chances are, it will be stuck, so you will often have to do some working back and forth, and beating on with a rubber mallet, and more working back and forth, possibly before you remove the shift rod, as if it hasn't been removed in a while, it won't want to be removed.

Now, the water pump will be wrapped around the drive shaft, on the top of the lower unit. There should be 4 screws holding the housing on. Remove those, then slide the housing up the driveshaft. Sometimes, the old impeller will remain in the housing, and sometimes, it will stay at the bottom of the driveshaft. Either way, there is a woodruff key inside the impeller. Do not lose that.

Now, pull the water pump plate off, and clean any gunk off of it, as well as any gunk out of the housing. Blowing compressed air down the passage won't hurt anything either. Reinstall the same as you put it apart. NOTE: Do not forget the woodruff key. That is a very common mistake. Also, when you reinstall the lower unit, you have to realign the water tube, as you slide it in place. The water tube is the copper tube with a tapered end that seats into the grommet on the top of the impeller housing. Usually, these take a little wiggling to realign, and it is crucial that they mesh properly.

 

[Usmctanker]

Thanks bass boy. Sounds fairly straight forward. Not sure if the problem is the impellor but seems to be a safe bet for 10 bucks since the thermostat was in such rough shape.

 

[Usmctanker]

wow. 45 minutes and i'm done. much easier than i thought. thanks again bass boy

 

[bassboy1]

While it was definitely smart to replace it, as they do tend to go bad, I am not certain that the impeller is the reason you were getting no water. Unless they are badly bent, and blades are torn off, they will usually pump some water. I am thinking you have a blockage somewhere in the line. Also, it is generally not an acceptable practice to run without a thermostat. You can remove the internals of the thermostat, but you still need the outer piece to provide the correct restriction. In racing, (both land and water), it is common to remove the thermostat, but a piece is fabricated to provide the same restriction as a fully opened thermostat. Often times, this is made from cutting apart the old thermostat. Only thing is, without a therm, you will definitely want to warm it up under load (in gear, as opposed to idling in neutral at the dock while you park the trailer), as it won't warm up otherwise. Test it again, to make certain you aren't getting water, then we need to start looking for a blockage through the line.

I am working with the same issue on a '68 6 right now. Lots of sediment all throughout the cooling passages, and the thermostat housing was packed solid with sand. Been pulling pieces apart to clear and clean passages. I doubt yours is as extreme as mine, but all it takes is one mud dobber nest to block it up.

 

[Usmctanker]

Tested it after I got it put back together and i was getting a good bit of water. The old impeller was in bad shape. I am not getting a lot of flow at idle though. Today I will gut the old thermostat and reinstall it, since it might be a "back pressure" kind of issue. I stull think i should tear into the head when I get time and see if its clogged. Unless you know a better way to clean it out.