1974 85hp Johnson cuts off after 30 mins

[xxwulvexx]

Hi Guys<br /> I just got an 18ft 74 Aquasport with a 1974 Johnson 85hp....Engine looks great but after about 20-30 minutes of perfect use it just dies and doesnt want to start back up...if i sit for about 30 minutes it starts back up but runs very badly...stalling etc... i have had 2 people that saw me in the water tell me that they saw very little water pissing from the high end...but from what i have read on the posts im confused...some say it shoud be pissing constant and some say it shouldnt....ive tried to hold my hand on the top of the engine but its just to **** hot for even 1 second .... Can anyone help ?

 

[R.Johnson]

Re: 1974 85hp Johnson cuts off after 30 mins

If you can't touch it, it's too hot. Did your over-heat horn blow in the control box? If it got so hot as to stop running, and then hard to start. You may want to take a serious look at it.

 

[xxwulvexx]

Re: 1974 85hp Johnson cuts off after 30 mins

i dont have a temp gauge on this boat...i guess i need to install one...... i dont have an over heat horn either...at least i dont think i do....

 

[ezeke]

Re: 1974 85hp Johnson cuts off after 30 mins

The tan wire coming off the cylinder head on your motor should lead back to the control and the horn. To test the horn, turn the switch to the run position and ground the tan wire at the cylinder head. <br /><br />If there is no break in the wire, use a safety pin and some wire. Stick the pin through the wire and ground it to the block. This should sound the horn. If it does not sound off, you need to check the wiring back to the control, or replace the horn in the control.<br /><br />If the horn in the control does sound off when the wire is grounded, then the temperature senser is bad at the cylinder head and needs to be replaced.<br /><br />This will only tell you what you already know - too hot! <br /><br />The next thing that I would do is to replace the water pump. <br /><br />If that doesn't fix the problem, pull the heads and look for mineral build up in the cooling circuit.<br /><br />The thermostats (vernatherm) in your motor are difficult to replace, but may be a problem. On this motor, check that last.

 

[ezeke]

Re: 1974 85hp Johnson cuts off after 30 mins

One other thing, the water should be coming from the tell-tale constantly and should be very strong when you are running fast.<br /> <br />This is why I think that your water pump is shot. If you want to replace it yourself, buy the complete kit - you can get it from our sponsor. Fellows on this site can talk you through the change. It takes about an hour.

 

[xxwulvexx]

Re: 1974 85hp Johnson cuts off after 30 mins

Wow, <br /> thanks alot Ezeke for the info......You guys are fast on helping me out and it is very much appreciated !!!!!!!!

 

[R.Johnson]

Re: 1974 85hp Johnson cuts off after 30 mins

Ezeke: Did the 1974 have a tell=tale? Can an engine over-heat with a strong tell-tale?

 

[rickdb1boat]

Re: 1974 85hp Johnson cuts off after 30 mins

I don't know about the tell-tale on the 74', but my little 28 johnson was pi**ing like a horse and it was overheating. Put in a new pump and all was well. Then again, it was awhile since it had been changed. The blades had taken too much set to keep up.

 

[ezeke]

Re: 1974 85hp Johnson cuts off after 30 mins

To R.Johnson and Rickd1boat<br /><br />Don't know what you call the exhaust relief or tell-tale, but that's what we called it since I was a young man and I am 61. Point is: I own and run 1973, 1975 and 1976 V4s in this series and the check list is in the order in which I would check my own motors. <br /><br />It is certainly possible to overheat while getting the waterflow (which he said he was not), which is why I think he should make sure his horn is functional.

 

[11 footer]

Re: 1974 85hp Johnson cuts off after 30 mins

When was the last time you replaced your waterpump? It if so hot that you can't touch it you may have messed up things alot more inportant then the waterpump. Replace your waterpump before you run that thing again!

 

[R.Johnson]

Re: 1974 85hp Johnson cuts off after 30 mins

I did not state my last post properly. I know that an engine can over-heat with a strong tell-tale, but many people don't. They feel that as long as there is a visible stream, all is well.

 

[Solittle]

Re: 1974 85hp Johnson cuts off after 30 mins

The folks that seem to think that they do not need to cchange the water pump if they see even a small water flow out of the telltale are those who will later submit a post asking about what is a fair price to get their motor overhauled.