1958 Johnson Seahorse 5.5 HP Overheating (WITH PICTURES!!!)

Marcaronio

Cadet
Joined
Jun 23, 2011
Messages
26
In the instructions to tune-up my motor I am following it says, "You should also be able to touch the cylinder head and crankcase with your fingers and not get burnt." This is not the case for me. I just replaced the impeller and cleaned out the water passages throughout the entire motor and I can see water coming out of the exhaust when it is running now so I know that the impeller is working. I am worried that the water is not taking it's full path through the engine and is leaking into the exhaust before getting to the head.

I'm as new as new can be to engines let alone diagnosing problems, however, I started thinking it through and here is what I can think to check:

1. Check for leaks or blockage in the pipe leading from the impeller housing to the powerhead to lower unit gasket.
2. Check for leaks or breakage between the water path and exhaust in the powerhead to lower unit gasket.
(i believe the first place the water goes in the powerhead is next to the exhaust manifold, is this correct?) The blue is the path of the water while the red is the exhaust right?
3. Check for leaks or blockage in the exhaust cover.
IMG_5830_water.jpg

(i believe the second place the water goes in the powerhead is through the outer jacket of the head, is this correct?) The blue is the path of the water.
IMG_5831_water.jpg


I found 1 potential problem. Let me know if you think this could be causing water to not get to the head or even cool off the exhaust manifold cover.

In this picture of the exhaust manifold cover you can see a small hole near the top. Also there is no gasket or gasket material on this cover. Should there be? I can see water coming up out of this hole and boiling while the engine is running.
IMG_5832_water.jpg


Is it possible that water is leaking between the water passage on the left into the exhaust manifold because there is no gasket and is being boiled up and out of the hole in the exhaust manifold cover? Water should not be in the exhaust manifold under normal operation correct?
IMG_5830_water.jpg

IMG_5833_water.jpg
 

oldcatamount

Lieutenant Commander
Joined
Apr 4, 2010
Messages
1,740
Re: 1958 Johnson Seahorse 5.5 HP Overheating (WITH PICTURES!!!)

Yes there should be a gasket, and there should not be a hole in the cover. I believe you have found the overheat problem. Good diagnostics!
 

lindy46

Captain
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Nov 27, 2008
Messages
3,886
Re: 1958 Johnson Seahorse 5.5 HP Overheating (WITH PICTURES!!!)

Should be a gasket. That hole in the cover shouldn't be there. Looks like that cover shows signs of overheating at some point in it's life.
 

raczekp1

Lieutenant
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Mar 30, 2010
Messages
1,327
Re: 1958 Johnson Seahorse 5.5 HP Overheating (WITH PICTURES!!!)

hi.
i would look at pistons, bottom parts of pistons.
if motor gets overheating, pistons can do some friction with cylinder wals
 

Marcaronio

Cadet
Joined
Jun 23, 2011
Messages
26
Re: 1958 Johnson Seahorse 5.5 HP Overheating (WITH PICTURES!!!)

I ground down the inside of the manifold cover and built up the low spot and hole with JB weld. Any ideas on the part# of the gasket I need? Can I use rtv black high heat gasket maker?
 

jbjennings

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Jul 18, 2007
Messages
3,903
Re: 1958 Johnson Seahorse 5.5 HP Overheating (WITH PICTURES!!!)

Should be a gasket. That hole in the cover shouldn't be there. Looks like that cover shows signs of overheating at some point in it's life.

What an understatement!!! :)

If I had anything to add to the great advise you've already received, it would be to check the upper water tube grommet and powerhead to exhaust tower gasket. Also, I believe your motor has the carbon seal that sits on top of the drive shaft. THe carbon seal assembly should be put back together correctly with a new carbon seal. That motor got REALLY hot in the past. Since you have the head off already, put it on a pane of glass and check it for warpage.
Good luck, those are tough motors and I'll bet it will run nicely when you get it to stay cool.
JBJ
 

johnson18hp

Recruit
Joined
May 12, 2006
Messages
4
That cover should also be the same color as the engine block and yes there should be a gasket behind the cover.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
WHOA, an awful lot of misunderstanding here!!! Take a look at that exhaust cover plate. ONLY the one edge is water cooled. The rest of it has fire blowing at the inside of it, and it gets blisteringly HOT. That is normal and the way it was made. In fact those motors burned the paint off that cover during the first five minutes it was run after taking it out of the box.

Your motor does not look like it has overheated.

If you expect JB Weld to stand up to that temperature, you are dreaming. Get a new plate and a new gasket and get on with life.
 

nwcove

Admiral
Joined
May 16, 2011
Messages
6,293
the exhaust cover is obviously off an earlier 5.5, and the piston tops look awful clean to me :rolleyes:. just for reference sake heres a pic of a normal looking exhaust cover and head from a 57 5.5.



 

nwcove

Admiral
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May 16, 2011
Messages
6,293
crap....did the work of responding with pics.....only to realize that johnson18hp opened a 3 year old thread!! :facepalm:
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Double crap!!! Obviously I didn't notice that either. Oh well at least maybe we saved somebody else from doing all that un-necessary work on a motor that doesn't need it.
 
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