Hey All ! Please help with Question reguarding '75 Johnson 4hp...

[WATERTIMES]

I was reading some threads about water cooling and it made me want to ask about mine and how it works. I've had mine in a pail runing I don't see any water coming out of any ports their are some however down by the prop.
Can someone explain to me what I should be seeing when it's runing for my year and model?

 

[Vic.S]

Re: Hey All ! Please help with Question reguarding '75 Johnson 4hp...

No there's no telltale (pee hole) but i guess there is an exhaust relief hole on the leg. You should see a bit of water spraying out of there with the exhaust gases.

The main water flow does just come out down below with the exhaust above the prop.

Make sure the pail you are using is deep enough for the gear case to be well covered as the water pump is in the top of it.

If you spit on the cylinder head and it sizzles it's overheating. if you can touch it for a second or two its OK

You may find the exploded diagrams in the BRP Parts Catalog useful

 

[WATERTIMES]

Re: Hey All ! Please help with Question reguarding '75 Johnson 4hp...

Thank you for the info Vic S., It is very helpful to my questions,I think I recall
seeing beads of water drops but no mist spraying out,would this be normal as well?

 

[Vic.S]

Re: Hey All ! Please help with Question reguarding '75 Johnson 4hp...

I'm not sure where the exhaust relief port is on that one. Immediately below the two halves of the swivel mount I guess in the plain bit of the leg that goes down towards the gear-case. You should see exhaust gas blowing out from there together with a few drops of water.

Most important thing is to satisfy yourself that the engine is not overheating.

Don't forget that pump impellers don't last for ever. Routine replacement from time to time is a wise precaution.

 

[Chinewalker]

Re: Hey All ! Please help with Question reguarding '75 Johnson 4hp...

Hi Watertimes,
If you don't know when the impeller was last replaced, replace it. It's about as easy as it gets on that motor, as there is no shift linkage to worry about. Make sure the o-ring at the top of the driveshaft is intact and grease the splines liberally before reassembling. New impeller should leave you enough change from a $20 bill to buy a cheap lunch....
- Scott