4hp johnson running hot

sambrigman

Petty Officer 1st Class
Joined
Jan 29, 2010
Messages
210
I have replaced with complete water pump replacement, Still running hot. Removed cylinder head, water coming from all holes on bottom cyl. none from top cylinder. Any ideas? thanks guys
 
Joined
Sep 28, 2020
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When you say you removed the cylinder head, do you mean the cylinder cover plate, or the plate and cylinder head? Did you have water coming out the tell tale?
 

Crosbyman

Rear Admiral
Joined
Nov 5, 2006
Messages
4,910
when you installed a new impeller did it have all it's vanes or some broken ??

some bits may have been circulated up the engine

try blowing out the water passage holes at the rear of the water jacket


one supplies water the other is likely an exit so don't expect water from both ..
 

sambrigman

Petty Officer 1st Class
Joined
Jan 29, 2010
Messages
210
The old impeller looked fine, i had the new one so i replaced it.i blow thru all the holes and only 1 hole blows air out the exaust holes. Is it possible that only 1 hole is intake?
 

Crosbyman

Rear Admiral
Joined
Nov 5, 2006
Messages
4,910
see picture...... water comes from the top drains at the bottom


i would think that air should pass freely in or out of the water jacket flow route

try fishing a weed wacker string in both water supply and exit routes of the jacket ... keep probing


Colonoscopy.... if nothing works you could try lifting the power head of it's base and work from the bottom up
 

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oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
With the lower end removed, push hose water up the tube (engine off) to flush. Note exit as you have been doing. Flush downward as well if the heads are off. Water should exit into the leg. The end of a hose quick release can work to reduce the circumference of the hose outlet.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,033
The exhaust cover is not fully water cooled and can get quite hot.
 

sambrigman

Petty Officer 1st Class
Joined
Jan 29, 2010
Messages
210
the top cylinder is getting to hot to touch, all the exhaust holes are showing exhaust, almost no water
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
36,033
Water pump impeller MUST be fully submerged in water to work.---Water must be 8" above the impeller.
 

Crosbyman

Rear Admiral
Joined
Nov 5, 2006
Messages
4,910
back to basics..... if you force air or water up the water tube (with the l.u. removed ) does the air/water seem obstructed if not clean the water pathway remove the PH of the base it need be !

if all seems ok ..... then the water pump or inlet to the pump is not working properly

did you inspect the water inlet to the pump

when you worked on the pump housing did you clean out the small purge hole in the top casing it is hard to see but clean it out
 
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