Johnson 5HP 4 stroke water circulation

[maghdubha]

when I start my motor in a barrell of water the pressure initially through the peehole is good and the motor is going fine
then after about a minute the peehole dries up to a trickle and I have to shut the motor off to prevent overheating
I have serviced the motor, engine oil.gear oil, replacement impeller and thermostat but still have this problem
I removed the gear box and water pump and attached a hose to the water intake pipe and all is well i.e. the motor runs perfect and there is a continual flow of water through the peehole and exhaust
I think I caused this problem when I replaced the impeller
is there a gasket between the water pump cover and the housing it sits on
while I am a novice to outboards I do have mechanical ability
however I cant solve this problem
help

[Solarman]

First off, if you ran it dry, it may have damage impeller after installing it. If not, does the exhaust go through the prop on your motor, or just the back of the midsection? I'm not familiar with 4 strokes, or your motor. However, some exhaust through prop motors have grommets that seal the exhaust and water Chambers. If those grommets are damaged, exhaust gases can interfere with water pump pulling water.
Another possibility (again, not familiar with your motor), if you have a by-pass valve in the water passages, it may be stuck in the open position, where when your thermostat opens the by-pass should close some to allow full flow to go through cooling passages. Generally the by-pass allows water to go directly to exhaust, unless thermostat opens.

Boats.net has changed their web page for parts, and am unable to see parts diagrams on any motors, so I am unable to verify what parts are on your motor. Best bet is reference your service manual for your motor.

I had hoped someone with more knowledge of your motor would help you. Boats.net - moderator? For example.

Sorry I can't help you more. Good luck.

[maghdubha]

solarman
thank you for showing an interest
i was beginning to think this forum had dried up
i took off the waterpump top housing and took it to a marine parts dealer
the housing that the impeller spins in is structurally ok however the exhaust vent that directs the water up to the main engines is damaged and restricting flow
This is hard to see initially but the mechanic took out the stainless steel sides that the impeller spins against and the damage could then be seen
I am ordering a new pump housing
I think I have uploaded 2 pictures which hopefully will show what im talking about and may assist someone else
Thank you

[Solarman]

Thnx for the update, yes, your housing looks bad. Keep us posted once you have the new parts installed.

Good luck.

[maghdubha]

ok i got the new pump housing at last
unfortately it came with all the parts
metalplates gasket grommets impeller and housing
it was quite expensive
however i have fitted it succesfully and the motor is going very well with water coming out the peehole
the flow isnt terrific but as i dont have any thing to compare it with
i have it going in a barrell and next step is out on the rib
hopefully it will go ok
thanks for your help

[maghdubha]

sorry for not coming back sooner but I only got trying out my outboard recently
the peephole still wasn't going great
anyway I put it back in the barrel and got an airline going which I pumped air back into the peephole with the engine going
this definitely did the job
I had to repeat it a number of times
but the peephole is pumping water out to beat the band and the motor is really going well
maybe this is not the proper procedure but it has cleared any blockage
hopr this helps someone else

[Solarman]

Thanks for the update.

i'm glad you were able to clear the problem.

Happy boating.