Is my outboard cooling system working?

N

Narojobra

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Jul 19, 2010
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11
I just fired up a Johnson 75 that I just acquired and have no clue on its history. It seems to run great but I want to be sure before I set out on the lake. I want to be sure that water is circulating for cooling. Because its a 1977 it does NOT have a tell tale. I have a large plastic container with the prop submerged to the anti cavitation plate. The water intake is submerged and the water discharge is above the waterline. Is this an ok way to let the engine run and test for water flow through the motor? I don't want to damage anything while testing it.

I am brand new to this and am assuming that I should be able to feel suction at the water intake and see water exiting at the discharge. Is this correct?

I also have a hose muff that I can attach to it but I thought submerging would be a better idea.

So what do you guys think?
 
N

Narojobra

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Jul 19, 2010
Messages
11
Re: Is my outboard cooling system working?

I do plan on installing a temp gauge in the future but for now I just want to be sure that water is circulating through the motor. I let the engine idle until the head was too hot to touch. Water never seemed to circulate. I opened the thermostat housing and the thermostat is opening. Here's a dumb question, does the prop need to be engaged in order for the water pump to pump or is it supposed to circulate water even when at idle?
 
Silvertip

Silvertip

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Joined
Sep 22, 2003
Messages
28,771
Re: Is my outboard cooling system working?

If the prop needed to be turning to cool properly every outboard on the planet would be overheating. The answer is NO! The water pump is driven by the drive shaft which is direct coupled to the engine crankshaft. So as long as the engine is running, the pump is pumping -- unless of course it is trashed.
 
N

Narojobra

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Jul 19, 2010
Messages
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Re: Is my outboard cooling system working?

I guess that answers my question that my pump is bad because it wouldn't move any water through the motor as it sat idling in a tub of water. Time for a water pump rebuild?
 
W

wilde1j

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Joined
Apr 15, 2002
Messages
5,964
Re: Is my outboard cooling system working?

If the pump hasn't been done recently, sounds like a plan.
 
N

Narojobra

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Joined
Jul 19, 2010
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Re: Is my outboard cooling system working?

Update....

I ordered a water pump rebuild kit and was amazed at how easy it was to do. Once I reassembled everything there is a very noticeable difference. Water is now blasting out the exhaust and exhaust relief. Seems to be working great. Next step is a full on lake test to see how it does at full throttle.

I would like to do a tell tale. I have seen the sticky on this forum and seen the update info from Johnson. I'm still a little confused about where to drill the hole. Can someone give me good info based on the included pic?

tell+tale+locations.jpg


Thanks for the help guys. I am sure there are more issues coming.
 
N

Narojobra

Cadet
Joined
Jul 19, 2010
Messages
11
Re: Is my outboard cooling system working?

bump....

Looking for where to locate my tell tale.
 
D

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: Is my outboard cooling system working?

I think you need to locate the fitting as high as you can, the top of the cylinder head.
Did you try a search, I think it has been discussed several times on the forum.
 
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