1981 E70ELCIH - water stops flowing out tell tale after 5 - 10 min

[mobisware]

Went to take the boat out recently. Started up ok, noticed the tell tale flow looked ok, let it idle while packing on the gear. After 5 - 10 min, I noticed the water stop flowing out the tell tale. I turned off the motor and got a little smell of burnt oil. After letting it cool off I hooked up the muffs and noticed a dribble out the tell tale. It started up ok and had a very strong flow out the tell tale for about 5 - 10 min. Then the pitch of the motor dropped, I looked back and there was no flow out the tell tale. I turned off the motor and got a little smell of burnt oil. I attempted to inspect the thermostat however it looks like someone else already took it out. I don't know how to check the pressure relief valve. Any tips would be appreciated.

 

[Bosunsmate]

You a quite possibly sucking up air using the muffs. In most motors thats not too dangerous as they have a bleed off system. The problem with your motor is it didnt have that system so air slowly builds up at the top of the engine and it overheats the motor.
Heres a link to the sevice bulletin.
If that doesnt fix it then get back for more ideas but if your telltale does not come from the top of your motor it must be moved there.

I did this fix to my 1982 and it now runs fine on muffs

http://forums.iboats.com/forum/engi...aq/228380-johnson-evinrude-adding-a-tell-tale

 

[WernerF]

The service bulletin concerns only the 56 cu in motor 1986 thru 1994.

 

[Bosunsmate]

The service bulletin concerns only the 56 cu in motor 1986 thru 1994.

yeah but its applicable to earlier motors and different sizes too. As the poster says its advised for "early 80s and late 70s" motors, he just didnt have the service bulletins for all those years. The same principle applies on all motors within that age range, get the outlet from the engine up the top as shown and explained in the rest of that post.
Replacing waterpumps etc will have no beneficial effect unless this is done

 

[mobisware]

Here's some more background information: The boat is still in the water, at my dock, so after I put on the muffs I tilt the motor back down into the water before starting it.

Thank you for the service bulletin link! I'll look into that. I'm wondering if the pressure relief valve is stuck since there is some salt deposits. I'm not sure where the air is coming from but maybe moving the telltale to the top will help (it is currently in the original location).

 

[Bosunsmate]

so you put it on muffs and drop it in the water, ive never seen that done before.
Pressure relief valve (poppet valve) works only at higher rpm so it wont be your issue just going slowly.
Id be cleaning out the water channels and removing the head if it was me as in a salt water motor the channels around the cylinders get slowly filled up with salt deposits no matter how well you flush.
When you have the head off, its a piece of cake to then install the telltale at the top of the engine too

 

[Bosunsmate]

The other thng is you say the pitch of the motor changed which means it might of had some overheat damage, hopefully if so only the headgasket but you might want to do a compression check before removing the head. A compression testers about $8

http://forums.iboats.com/showthread.php?t=313963&highlight=compression

 

[mobisware]

Well, I live on a river and keep the boat in the water all the time. I don't have a lift or a truck to trailer the boat.

Before all this the compression was about 120 on all 3 cylinders. I'll be sure to check it again as you suggested. Thanks for the info!

 

[Bosunsmate]

no worries, good luck