1990 3hp johsnon overheat

[robert53a]

I have a 1990 3hp Johnson that get too hot. I have change the impeller and still is running way too hot. Any thought on what to check next? Thanks. It sprays a little water then just stops and then heats up.

 

[Joe Reeves]

Re: 1990 3hp johsnon overheat

Possible problem areas would be:

1 - Something overlooked in the water pump repair.
2 - Water tube got forced up slightly, not fully inserted in pump grommet.... OR tube hit pump grommet improiperly causing it to fold over.
3 - Top water tube grommet swelling, acting as a shut off valve.
4 - Head gasket leaking slightly, cause a stalemate. Water coming up, combustion going down, water sits still.

I'd suggest removing the lower unit and cylinder head, then forcing air (or water) up the water tube to check for obstructions. This would also allow you to inspect the head gasket, the sealing surfaces of the head and block, and while you're there, clean out the water passages.

 

[robert53a]

Re: 1990 3hp johsnon overheat

Thanks Joe, I will go through this little motor and follow your suggestions and report my findings. The help is greatly appreciated.

 

[robert53a]

Re: 1990 3hp johsnon overheat

This is a follow up. So far Ive removed the head and exhaust cover on this motor and found no obstructions. I will check the lower for water pump efficiency soon. I have a question of impeller function. The impeller for this motor has three vains. In my manual the 4hp deluxe has 6. Both engines have the same cup liner and retainer pin part numbers, so I know that each will fit in both motors. Whats the difference? Thanks again for the help .....Robert

 

[raczekp1]

Re: 1990 3hp johsnon overheat

i had the same motor.
impeler also had 3 vanes.
pumps water fine

 

[robert53a]

Re: 1990 3hp johsnon overheat

Hi, this is a follow-up to this thread and an end to this motors overheat problem. It was by no means simple. i went through the whole cooling system, pulled the head and the side cover thoroughly cleaned every thing out. re-assembled with a new three vain impeller and it still heated up. I tried my garden hose tool on the water tube and noticed it took ever so little pressure to make this work and keep cool. To fix it I decided on a 4hp 6 veined impeller of the same style height and diameter. It now pumps enough water to keep it at 125 degrees at idle and 130 degrees at prolonged high speed. whether the passages are narrowed or what. it works and I'm happy. Thanks to everyone for you help......Robert

 

[MMcCawley]

Re: 1990 3hp johsnon overheat

Robert, do you have the part number to the 6 vane impeller? I have an early sixties johnson twin that is also overheating. The motor was given to me not running so I got it running and replaced the impeller but water still does not appear to be circulating efficiently (I am getting a mist out of the 8 small exhaust holes though). I am 95% sure that I replaced the impeller correctly and the copper tube was put back in place. Can anyone tell me how I can verify proper water circulation or provide any feedback. Thanks.

 

[Haffiman]

Re: 1990 3hp johsnon overheat

If remembering right, that engine has a plastic 'pin' in the water channel from exhaust cover to cylinder for some strange reason. I used to remove it to solve that problem.

 

[MMcCawley]

Re: 1990 3hp johsnon overheat

Thanks for the reply. I'm not quite sure I know which pin you're referring to. Would you happen to have a picture or diagram? Or better yet, does anyone happen to know where I might be able to download a manual? Thanks again!

 

[Haffiman]

Re: 1990 3hp johsnon overheat

Unfortunately it is not marked out in the catalog:
http://www.marineengine.com/parts/j...rer=Evinrude&section=Cylinder+&+Crankcase
But it is mentioned in the parts list #6 and called 'metering rod'. Remove the exhaust cover and check if it is in the channel/bore into the cylider.
You should even check out the water deflector #9 and replace, but then you have to remove the head.

 

[MMcCawley]

Re: 1990 3hp johsnon overheat

Great, thanks. I'll tear the motor back apart and look into it. What is the best way to verify that these engines are cooling properly since they do not have a "pee hole"? Should I expect to see any water coming out of the eight small vent holes? Thanks again, I'm looking forward to getting this little engine up and running again.

 

[Haffiman]

Re: 1990 3hp johsnon overheat

It will generally just be a 'mist' spraying out of the holes.

 

[MMcCawley]

Re: 1990 3hp johsnon overheat

It does have a mist coming from the holes so I'm assuming it is pumping to some extent. Obviously not enough to keep the engine temp down though.

 

[Haffiman]

Re: 1990 3hp johsnon overheat

If a mist and not steam it should be ok.