1978 johnson 70hp water issue

[dsujen]

Re: 1978 johnson 70hp water issue

1978 johnson water leak2 - YouTube

here is a longer video of the motor running. I let it idle for at least 10 minutes and ran it at higher rpms in neutral for short periods of time with no over heat on the muffs. I periodically put my hands on the heads to be sure it was warm but not hot. As I stated before, I took the boat out 4 times during the summer and went through all speeds and several tanks of fuel with no issues at all. I don't want to damage a great running motor by taking it apart because I know some of the bolts are frozen pretty good.

 

[Bosunsmate]

Re: 1978 johnson 70hp water issue

From what i could see it looks as though you only get steam out of the rear exhaust relief ports and the prop main exhaust. The water in that area in the video seems to be coming from the muffs.
There is no steam ever coming out the front so im not sure if your plate could be worn like the one Durban shows in his video.

Beats me. If it was me out of curiosity id remove the lower leg. Those very bottom bolts a stainless and have never given me trouble. The only thing that can is if the driveshaft is stuck into the upper crankcase spline. Depending on whats going on in your motor that may or may not be likely, if it is stuck you can just reinstall the bolts and go use the boat in the water as you have being until your impeller eventually wears out. You could drill a hole in the front casing to get more of that water out.
Thats all i can add hopefully someone else can give you something you would more like to hear

 

[xjdriver]

Re: 1978 johnson 70hp water issue

You should be getting more water out of those holes above the prop. Does the water get into the airbox?

 

[floridaboy41]

Re: 1978 johnson 70hp water issue

dsujen: Did you find what was causing the water to come out around the drive shaft. I ask because i have a 1993 60hp. Johnson that is doing the exact same thing. So far unable to figure out what is the cause.

 

[dsujen]

Re: 1978 johnson 70hp water issue

I'm still looking for answers. I have several people telling me several different things. I'm still trying to narrow it down.

 

[xjdriver]

Re: 1978 johnson 70hp water issue

I'm still looking for answers. I have several people telling me several different things. I'm still trying to narrow it down.

Your just gona have to do some detective work. Its really hard for us to tell you what exactly the problem is on these types of things, i would drop the lu and hook a water hose to the water pickup tube and see from there. Plus you dont have it running all the time.

 

[dsujen]

Re: 1978 johnson 70hp water issue

What will that tell me? That there is a bad water pump tube gasket? If so, would that cause water to come out of the drive shaft? That would be great if that was it. Originally that is what I thought it was, but I had an old time Johnson mechanic tell me that it is a rotten exhaust plate. I tried to by a new water pump kit off of him over the phone and told him why. He told me that was not the problem. He said that year an and type motor has a problem with the exhaust plate corroding. He said that it would be almost impossible to fix it because of corrosion. He said run it till it blows up, and he's a mechanic!

 

[xjdriver]

Re: 1978 johnson 70hp water issue

What will that tell me? That there is a bad water pump tube gasket? If so, would that cause water to come out of the drive shaft? That would be great if that was it. Originally that is what I thought it was, but I had an old time Johnson mechanic tell me that it is a rotten exhaust plate. I tried to by a new water pump kit off of him over the phone and told him why. He told me that was not the problem. He said that year an and type motor has a problem with the exhaust plate corroding. He said that it would be almost impossible to fix it because of corrosion. He said run it till it blows up, and he's a mechanic!

No, im thinking it will make it easier to pinpoint exatly where the water is coming from. Its not coming out of the driveshaft.

 

[floridaboy41]

Re: 1978 johnson 70hp water issue

I have the same problem with my engine and my mechanic told me the same thing it was caused by a plate corroded. He said just run it. He also said i could open up the drain hole below the drive shaft opening and that should help some. So that is what i plan to do.

 

[Bosunsmate]

Re: 1978 johnson 70hp water issue

Dsujen
Unless you drop the LU you wont find out whats causing it. So either do that or keep guessing.
If you drop the LU you can just bolt it back on as ive written in a previous post.
More than happy for you to give that johnson mechanic oracle status but ive read enough on this site to know that they arent always right.
Up to you now.
Floridaboy i suggest you start your own post and post a few pictures/video so everyone can see what your one is doing.

 

[Faztbullet]

Re: 1978 johnson 70hp water issue

Easy fix, drop the gearcase and replace o-ring and grommet on top of water pump. when these go bad they leak and allow water to climb drive shaft when running.

 

[dsujen]

Re: 1978 johnson 70hp water issue

I will drop the lower unit as soon as I get a chance. When I do, What am I looking for? Should I change the water pump assembly while in there even though it's not overheating? I don't know when it was changed last because I bought the boat/motor off a dishonest seller.

 

[Bosunsmate]

Re: 1978 johnson 70hp water issue

You a looking for a worn o ring and grommet on top of water pump and or blockage in exhaust somewhere.
Also just attach a hose onto the water inlet pipe and you will be able to see if water is coming out down the correct rear exhaust channel or is squirting out where it shouldnt be.
Dont forget to disconnect the shift rod before dropping the leg
Once its apart you can decide whether to change the pump. i always do it with any motor i get unless im provided with a receipt or the impeller looks and feels very new.

 

[boobie]

Re: 1978 johnson 70hp water issue

Fazt, I told him that in another post he has going about the water pump grommet and o-ring. Ran into same problem some years back where another dealer forgot to put them in.

 

[phillnjack2]

Re: 1978 johnson 70hp water issue

well iwould say its pretty obvious the block is full of gunk and no water getting through or the thermostat is stuck solid.
this would let him have a good tell tale as that comes out before water gets to run around the engine block and head.

trouble with lots of mechanics is they only want to work on later engines where they can make a simple job look fairly cheap, although the bill will be big.

I would drop the gearbox as stated loads of times above, and also take off the thermostat cover and see just how much water if any is getting to that point.

the impeller is obviously pretty good asto the join from water pump to pipe etc or he wouldn't have such a force of water at the top.

I bet the engine is well bunged up with limescale or salt !!!!! and a good back flush wont hurt it.

the gasket from mid to powerhead will need to be replaced as that has now been destroyed anyway.

corrosion will play a big part in getting the power head off, but brute force ignorance and a hot spanner will help.

like it is its useless and just waiting to blow up, so go for it and take it apart, you have nothing to lose but lots to gain.

can you hold your hand on the cylinder head for 10 seconds once its warmed up for 5 minutes ?

I bet that engine is full of crud.
hopefully youl get it done and have a nice engine still.

phill

 

[dsujen]

Re: 1978 johnson 70hp water issue

I can hold my hand on it for 10 seconds after being warmed up for more than 10 minutes. I checked it on the river after prolonged no wake zone speed and full throttle for long periods of time. Still was able to hold my hands on the heads for about 10 seconds. Same on the muffs in the driveway.

 

[durban]

Re: 1978 johnson 70hp water issue

i would stop the motor as soon as the water starts comming out then unscrew all 3 plugs get some one to watch for water comeing out of plug holes while you turn the key

 

[dsujen]

Re: 1978 johnson 70hp water issue

What plugs are you talking about?

 

[Will Bark]

Re: 1978 johnson 70hp water issue

He's talking about the spark plugs

 

[dsujen]

Re: 1978 johnson 70hp water issue

Would the motor run great like it does with water getting on the spark plugs? Not only does it run great, it starts right up cold or hot. Any tips on removing the power head? There are 2 small bolts near the driveshaft that look like they need to come off but I cant get to them.