1978 johnson 70hp water issue

[dsujen]

I have a model 70EL78c 70hp johnson that has water entering the engine compartment when running. I talked to a mechanic and he said run it till it blows up because to fix it I must remove the power head and replace the exhaust tube gasket at the base of the power head. He said nearly impossible because of corrosion.He also said since it was used entirely in salt water that the aluminum housing could also be rotten. Today, I talked to a parts guy at a boat place and he said that it could be that the water pump is pumping too much water and there is a drain hole at the bottom of the exhaust tube near the shock absorber that might be plugged up causing the water to leak into the engine compartment. He said that the driveshaft is inside a pipe and the water pumps through that and if it has too much water pumping that it can leak into the engine compartment if the drain hole is plugged up. He said that they drill the drain hole bigger at the shock absorber to fix the problem. Ever hear of that? The motor has 130-135 psi on cylinders and runs and starts great. I took it out on the water 4 times this summer with water entering the engine compartment with no problems. I would like to stop the water from coming into the engine compartment but I don't want to ruin a perfectly running engine by breaking something while taking it apart.

 

[orbanp]

Re: 1978 johnson 70hp water issue

This sounds more like a corroded exhaust housing.
It is also a fair assessment the you probably will have trouble disassembling your motor.
On the other hand, if left untouched, the corrosion could get to a point that eventually cooling water would enter the cylinders through the exhaust ports. That will ruin your motor in short order, the cylinders could get rusty, con-rod bearings could get rusty during longer periods non use.
Do a search on Durban's posts on exhaust cover repairs, desalting of engines.
This a well known issue with the 3-cylinder engines.

Good luck, Peter

 

[boobie]

Re: 1978 johnson 70hp water issue

Have you ever seen EXACTLY where the water leak is when running it ??

 

[xjdriver]

Re: 1978 johnson 70hp water issue

Have you ever seen EXACTLY where the water leak is when running it ??

This^

 

[boobie]

Re: 1978 johnson 70hp water issue

Huh????

 

[dsujen]

Re: 1978 johnson 70hp water issue

yes. it is coming up from the base of the motor and filling the engine compartment from the bottom up.

 

[Bosunsmate]

Re: 1978 johnson 70hp water issue

By engine compartment do you mean inside the cowling cover, not inside the pistons cylinders etc?
No such thing as a waterpump pumping too much water.
Drop your gearbox and plug a hose to the inlet tube.
See if that causes the water to build up. If it doesnt you probably have something blocking where the exhaust housing thins out in the gearbox leg.
You can also put a torch up and see whats happening up there and also you can unblock all the drain holes in the leg at the same time.
Dont run it again unless you want to get pissed off that you killed your motor over a couple of hours at the most maintenance that you can do yourself

 

[classiccat]

Re: 1978 johnson 70hp water issue

I had a leaky '75 70Hp (link). Both the exhaust manifold & the powerhead-to-base gasket were leaking.

If you're comfortable dropping the LU, you can hook a hose up-to the water tube to help isolate the leak (s).

 

[boobie]

Re: 1978 johnson 70hp water issue

Sounds like power head or side cover gaskets.

 

[dsujen]

Re: 1978 johnson 70hp water issue

Water is filling the lower cowling cover. Today I was able to remove the cover around the base of the motor. I'm going to run it to see exactly where the water is coming from when I get a chance. Bosunsmate, do you mean drop the lower unit like for water pump replacement? You don't think I need to remove the power head? I tried to move one of the six bolts holding it and they didn't budge. Before I use heat I want to try to run it and see where water is coming from. There are two small bolts in the front and back of the motor that look like they need to be removed to take off the power head. I can't get a wrench on the ones near the front. Do they need to come off to remove the power head? I don't have a shop manual. What do I need to take off to take the power head off?

 

[dsujen]

Re: 1978 johnson 70hp water issue

Bosunsmate, The bolts I'm talking about are on the parts break down from ishopmarine.com. Part 64/ part # 0319358 4 bolts. Do I need to remove these to remove the power head, if so how? Because I can't get a wrench at the front two. Also part 16/ part# 0309280 6 bolts will not budge yet. I'm assuming I need to remove these positively?

 

[boobie]

Re: 1978 johnson 70hp water issue

Before you try removing the P/H, test it to see exactly where the leak is coming from.

 

[kenmyfam]

Re: 1978 johnson 70hp water issue

Agree with those suggesting isolating just where the leak is coming from.

 

[Bosunsmate]

Re: 1978 johnson 70hp water issue

Hi, no i didnt mean to remove powerhead. My suggestion was to drop the gearbox and then put a hose onto the water inlet tube and see what happens.

However i now think you should do as above since you have the lower cowling removed, look to see if you can see where its leaking from.
If that doesnt help, drop the gearbox as you will need to do that if you need to remove the powerhead anyway.
To drop the gearbox you remove bolts at the bottom of the engine. Probably best you post some photos with what you are up too as it makes it a lot easier to double check with what you a writing about

 

[dsujen]

Re: 1978 johnson 70hp water issue

motor video - YouTube

I found the leak today. When reved up water comes out of the drive shaft near the base of the motor. Please check out my video on you tube. Thanks

 

[dsujen]

Re: 1978 johnson 70hp water issue

I forgot to mention that after running the motor on muffs in the driveway I noticed that only a little bit of steam,no water came out of the exhaust relief holes at the top of the exhaust tube. I had the motor running for about 20 minutes at various rpms in neutral.

 

[Bosunsmate]

Re: 1978 johnson 70hp water issue

Thats strange.
What i can notice is that your telltale is working. What you a saying sounds like your thermostats arent working.
What i noticed by freezing the first couple of frames is that even though the telltale is pissing there is no water coming out of the exhaust in the prop too only steam.
Id like to see a video taken from the other side and zoomed out . there looks like there is a stream of water coming from somewhere on the other side.
Also run it at lower rpm and not for long, this is a possible dangerous overheat situation so go gently and let the motor cool down between trials until this is sorted

 

[Bosunsmate]

Re: 1978 johnson 70hp water issue

Your exhaust gasket may be blocking the exit but id really like to see the other side before suggesting you remove the lower gearbox

 

[xjdriver]

Re: 1978 johnson 70hp water issue

The spent cooling water exits thru the holes back and just above the anti cav plate, some also comes out the prop, somethin dont look right about where the water is surging up out of is there a piece of housing broken?

 

[durban]

Re: 1978 johnson 70hp water issue

replace the adaptor gasket & torque the power head to adaptor becarefull when you see this like in my photo a hole eaten into it from a leaking gasket & sea water i fixed this one with my cement powder & epoxy formula
by the way i fixed my m8ts exhaust on his car with the same formula he drove to another city 6 hours away & txted me saying thank very much its still working