1966 Johnson 40hp water pump

fixmyboat

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Joined
Aug 31, 2010
Messages
6
When I got this motor home it was not running. the Flywheel and pull starter was off and in the back of the boat. The electronics were hangin loose, no screws on the points condenser and coils. I have never worked on a boat motor before so this has been a project. All the screws and bolts were lost, I called and asked if they had them but they had no idea where they were, so I had to buy everything new. Anyway I got everything back together and had to take the carb off and clean it. I was all gunked up. I got the motor running real sweet but there is no water coming out of the exhaust port. I keep hearing about the telltale, my Clymer manual doesn't show it or explain it but I read something about it. I have water running out between the Lower Unit and the Gear Case, is that normal. I think I am going to drop the Gear Case and have a look at what is there. the guy I bought the boat and motor from said he had the lower unit rebuilt because the gears were stripped. He said he paid more to have it rebuilt than what I paid for the boat, motor and trailer. The more I work on the motor the closer it seems to be coming together. Any suggestions would be appreciated.
 

fixmyboat

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Joined
Aug 31, 2010
Messages
6
Re: 1966 Johnson 40hp water pump

One more question. Does the thermostat keep the water from flowing out the exhaust port until it gets hot enough to open it. I haven't run it up to any sugnificant temp as I have been afraid of doing damage to the motor. I run it until it feels warm to the touch and then shut it down. Should I run it a little longer to see if the water begins to flow. I don't want to do more than is required but I also don't want to ruin a perfectly good motor.
 

oldcatamount

Lieutenant Commander
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Apr 4, 2010
Messages
1,740
Re: 1966 Johnson 40hp water pump

Your motor may, or may not, have a tell tale but if it does you should be able to see it easy enough. Water should come out of the tell tale or at least out of the exhaust housing almost immediatly after starting the motor. After it's run for about 2 minutes, touch the head with your finger, if you can hold your finger there for the count of 3, it's cool enough. If not, then you should shut the motor off and look at an impeller replacement
 

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: 1966 Johnson 40hp water pump

2 things, no muffs- it need to be in a barrel with the water over the cav plate by 3 inches or so and it has no tell tale, only a hole coming out the back of the midsection.
 

Aratsman

Seaman
Joined
Sep 12, 2010
Messages
62
Re: 1966 Johnson 40hp water pump

You will get a fine mist out of the hole in the center of the exhaust housing along with exhaust. As the thermostat opens, the amount of water blown out of the exhaust hole will increase. Give it about a minute to see the first water come out and monitor the heads like the previous post said. DO NOT USE MUFFS!!!!!! This must be in a barrel in order to operate. There is no "pee" indicator on this motor. It can be fitted with one, I have seen the post here somewhere. Do a search on it. If you are going to pull the lower unit, change the impeller anyway. They are cheap and you will know how long it has been in there.
 
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