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1986 70 HP Johnson - alarm buzzer going off

N

Naxas

New member
1986 Johnson 70 HP

Hey guys,

First of all thanks a lot for all the advice and shared know-how provided by this community!

Before posting this thread I read through old posts and tried to find an answer - unfortunately unsuccessfully.

Ok here is my problem:

A few days ago I went on a fishing trip and we wanted to get to an island quickly in the morning so I really revved up the engine.
I would say 3/4 throttle.

After a few minutes an alarm buzzer came on and I immediately switched the engine off to prevent damage.
For about 5 minutes whenever I turned the key (without starting the engine) the alarm sounded again. After about 5 minutes it stopped and I could easily turn the engine on without problems and travel on.

At lower rph that is... as soon as I open up the throttle 3/4 or full the alarm goes off again within few minutes.

Now the oil injection (VRO) has been disconnected years ago and 1/50 mix fuel is being used.

I read in a previous post that the head gasket could be a cause. I bought a compression tester and all three cylinders show almost the same exact compression: 125 PSI.

I never had this problem until I recently changed the battery cables.... however this should not be a problem. I got bigger and better cables and used good insulation material near the motorblock.

Water pump is nearly new and water flow is perfect.

Any suggestions what could be the issue and how to fix it?
I won't disconnect the alarm buzzer though... that's not an option.

Thanks

PS. Anything under 3/4 throttle is perfect and no problems at all... could probably keep going until I hit Antarctica
 
Buy a cheap temp gun and check the temp on top of the block when running it. You also could have a bad horn.
 
Well I have had a look at the Thermostat. It looks in pretty good condition. There was a littlebit of build-up inside it, however it really doesnt look too bad.

Well before I buy a temperature gun... I did put my hand on the powerhead and counted to 5 so it wasnt extremely hot.

I will check the horn next. It is an engine that has only been run in saltwater for last 28 years but it has been really looked after and is in a good condition.

20140217_215620.jpg
 
I had that same problem on an 82 rude the temp sensor in the head was bad 2 chk that take it on the water and unplug the senso and see if it quits u say u can keep your hand on the head so it doesn't seem to be getting hot they use to be cheap and all that holds it in is an o ring but mine was discontinude and i was luck 2 find a used on that was still good luck 2 u
 
Had this same problem on my 1985 Johnson 150 and it turned out to be bad diverters in the portside head. These will go bad especially if the engine gets overheated at anytime but my understanding is they go bad over time especially in salt water. Pulled both heads and removed the old rubber diverters and matched them to new rubber tubing I purchased at NAPA. Old diverters were collapsed and misshaped to where they were causing poor circulation through the heads. I didn't need to pull the water covers, which is good since I had put new gaskets, thermos, and pressure regulators, etc. in. Just pulled the heads. Also, the previous suggestion about the heat gun is a good idea, I did that and was able to determine which side was overheating. Being able to touch the head is not a good enough test.

John
 
Sorry thought maybe basic same design for cooling through the heads. Another possibility is an incorrectly installed water tube grommet.
 
Wanted to try and replace the buzzer, may be stuck in on position. I disconnect the temperature sensors and the alarm keeps on going off anybody know what that buzzer unit it'is called I tried looking it up can't find it. I have a 140 Johnson 1993.
 
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