1978 Johnson 70 HP tell tale operation

[billy4hp]

Hello all, pretty much an outboad newbie so take it easy on me...

My new to me boat has a 1978 Johnson 70hp on it (sorry don't have the tag in front of me for the serial #) anyways I was running it on the hose tonight and noticed that the tell tale would spurt then stop, spurt then stop... It would easily pea a good 6 foot solid pressured stream when it was peeing...


I grabbed an temperature gun and check the head temp (at idle) was around 110 deg F, I could lay my hand on it and not remove it, the exhaust housing temp was a bit higher at 130 deg F, after the engine was running for awhile water started running rapidly out of the water holes in the lower leg (what I assume is the water out)...

Now this engine was "supposed" to have a new impeller in it, I have ordered the service manuals for it but it hasn't arrived yet....

So from my info does it sound like I have a plugged tell tale (exhaust housing) or does it have a impeller issue?

I know for the piece of mind that I should change the impeller and most likely the whole water pump assy. to know it is changed and new, but I don't want to change the impeller when I should be attacking another area of the engine...

When is the tell tale supposed to pee, all the time when the engine is running or only when the thermostat is open?

Thanks for the advice....

Billy

 

[reelfishin]

Re: 1978 Johnson 70 HP tell tale operation

I'd try it in a barrel of water before getting to worried. Water flow on a set of ears is limited and not always enough to give a good tell tale stream. My 1986 70hp does the same thing on the ears, but is fine if I fill a trash can full of water. My impeller and t-stat are new.
I also find that repositioning the ears can help too, mine is pretty sensitive to how they have to be one there.

If the stream is weak when in a barrel, then I'd investigate further.
I've had dozens of outboard where they said the pump was new but found it worn or badly dryrotted.
I usually check any motor I intend to run or rely on, I also replace the impeller pretty regularly, if for nothing else but piece of mind.

 

[tashasdaddy]

Re: 1978 Johnson 70 HP tell tale operation

it is a common mistake to pinch the grommet at the water pump, where the water tube is inserted, restricting the flow of water.

those motor use the exhaust relief post as the tale tell, sometimes you get a mist, others especially when the tstats open you get a stream.

you can add an actual tale tell hose to the motor which is much more reliable. but remember tale tell only indicates the water pump is pumping. NOT that the tstat is opening and cooling the motor.

http://forums.iboats.com/showthread.php?t=222677

 

[iwombat]

Re: 1978 Johnson 70 HP tell tale operation

I think the '78 actually had the real overboard indicator. At least the v-4s did and I think the triples did too.

If anything, the muffs should produce a stronger stream than in the water, at least if you've got the pressure turned up on the hose. And, the tell-tale output is prior to the t-stats so it should have continuous output.

It's possible the impeller was replaced when what was really needed was the full water pump assembly.

 

[tedious]

Re: 1978 Johnson 70 HP tell tale operation

Billy, does your water tap run off a well, or city water? If the former, that could be responsible for the cycling you are seeing, as the well pump kicks on and off. My 1989 70 does not put out a strong stream unless I hold the muffs tight on the engine, otherwise it just spits.

Tim

 

[billy4hp]

Re: 1978 Johnson 70 HP tell tale operation

Thanks everyone for the replies, I love this forum...

Anyways we are on city water, the "tell tale" hose does come from the exhaust cover so I guess it is not a true "tell tale" in the sense that it is not tapped into the head as some other models (I have been search the forums and from what I have read the true tell tales go elsewhere)...

So I am not going to stress about it, rather I will order up a whole pump repair kit and wait for my manual to arrive..

I imagine I better order up an owners manual while I am at it...

From the other searching I have done I see Tasha isn't too fond of adding a water pressure gauge or any gauge for that matter , but if I did add a water pressure gauge what should the block pressure be? I remember my father's 1989 Mercury 200 to run about 3 to 5 psi or so.....

Thaks again,

Billy

 

[iwombat]

Re: 1978 Johnson 70 HP tell tale operation

As long as it's tapped into the water jacket someplace, it's a real tell-tale and you've got one.

Before '78 the only indication was out the exhaust ports post t-stats.

 

[billy4hp]

Re: 1978 Johnson 70 HP tell tale operation

As long as it's tapped into the water jacket someplace, it's a real tell-tale and you've got one.

Before '78 the only indication was out the exhaust ports post t-stats.

Does mine being in the exhaust make it less positive as it is a larger volume (less restriction)? Just curious as the link to adding a tell tale it installed in the block rather than the exhaust housing...

 

[iwombat]

Re: 1978 Johnson 70 HP tell tale operation

Putting it at the top of the block lets any air pockets out and removes the potential for siphoning. That's the only real difference. You can address #2 by running the tube up over the block and back down as per the service bulletin.