Johnson 40hp high speed running...

[gopud]

Hi all,
I am new to the site and very pleased that I have joined as it seems to be a very comprehensive site with many helpful people.........sooooooo....
I am new to boating and need a little advice:

My 40hp Johnson starts and runs very well but at high speed the engine is not happy and 'hunts', will not maintain the speed, also after a short time there is smoke coming out of the water port and not much water (if any :redface
What I am wondering is if the water pump is no good and the engine is over-heating at high revs?

Any, or all of your help would be appreciated. Oh also it's quite an old engine, has electric start but not oil injection, compression is very good.

James

 

[tashasdaddy]

Re: Johnson 40hp high speed running...

year and model # would help, they been built since 1960. sounds very much like you need water pump service. the faster the motor runs the stronger the pee stream.

 

[gopud]

Re: Johnson 40hp high speed running...

Sorry, just found model number 40RL73D therefore built 1973.
Would a water pump repair solve the high speed problem and how hard is it to do (engine lift needed?)

James

 

[Giz_]

Re: Johnson 40hp high speed running...

Replacing a water pump on your engine is not particularly difficult, nor expensive.

You shouldn't need and engine lift.

Whether it will cure your high speed issue remains to be seen.

Do NOT run it again until you address the water pump problem. You can COMPLETELY ruin the engine quite easily.

Ask more questions as they occur.

I'm sure other, wiser folks than I will chime in.

Good luck!

 

[gopud]

Re: Johnson 40hp high speed running...

Many many thanks Giz, I was under the impression that running the engine with a poorly water pump would be hazardous but without being told I would probably have 'got around to it' at some point, but will now give it greater priority.
So can anyone give me a few quick pointers where I should split the engine to get at the water pump and is the thermostat in the same area? Also where would be the best place to get parts (as in other than a boat yard)
Help would be very much appreciated.
James

 

[Giz_]

Re: Johnson 40hp high speed running...

Many many thanks Giz, I was under the impression that running the engine with a poorly water pump would be hazardous but without being told I would probably have 'got around to it' at some point, but will now give it greater priority.
So can anyone give me a few quick pointers where I should split the engine to get at the water pump and is the thermostat in the same area? Also where would be the best place to get parts (as in other than a boat yard)
Help would be very much appreciated.
James

Dang....sorry I missed your post!

Still need help, or have you gotten it taken care of?

You would split the lower unit at the cavitation plate. You should see 4 or more bolts there.