'86 70hp johnson overheated....

[wbpope]

UH, oh,....First time out on a "new" engine (sea trials) and she gets RED hot cuts off....not good....

She ran fine in the driveway previously but, as I am new to outboards...a deisel guy and sailor primarily..I am at a loss as to where to begin..

Can one of you fine folks point me in the right direction..maybe a diagram and or some pictures of the cooling system? I can't seem to find ANYTHING!

 

[david_r]

Re: '86 70hp johnson overheated....

welcome to iboats!!


was the pee stream puttin out water?

did you put in new thermostats and a new water pump?

you can go to http://shop2.evinrude.com/ext/index.aspx?s1=9c60db3eafc1f4b20ccd2da688b6ec1c and get exploded diagrams and complete parts descriptions.

 

[wbpope]

Re: '86 70hp johnson overheated....

No, I didn't....the engine had recently been overhauled (or so I was told) and the carburetors rebuilt.
Like I said, I am new to outboards and wouldn't have thought to do that...in fact, I have NO idea where they are or what the cooling system looks like or how it works...
I have been to the site you posted but, it does not illustrate the cooling system, In fact, I haven't found anything that does that is not available to techs only.
I need some help....
If this were a diesel or 350 Chevy I'd be in fat city!....but, it ain't!

 

[david_r]

Re: '86 70hp johnson overheated....

the water pump is in the lower unit on the bottom of the drive shaft...............its rubber so dont run it without water............ if you already have there is where you should start for sure.

the thermostats are usually at the top or the bottom of the eng as you look at it from the rear................. the thermos are a lil different from cars but same principle....... they have a bypass for wide open throttle.

you really need a manual of your own but you can go to googlebooks.com and get partial repair manuals for free.

the site i gave you has everything exploded but not always in the diagram you would expect it to be................ somtimes you have to search the surroundings to find the part # you are looking for.

as far as the cooling system if you drop the lower unit you can put a waterhose to the water pick-up tube and see if water comes out the tale tell/pee hole.................... better to take off the thermostats too and give it a good flush.

 

[scrampbell]

Re: '86 70hp johnson overheated....

Hey WBPope. The key components of an outboard's cooling system (as I understand them) are...

1) Impeller (water pump): It's in the lower unit and pulls in water from the grate like vents above the prop. It should generally be replaced regularly (every season or two depending on how and where your motor is used). There's an indicator that will let you know your impeller is working called the telltale. As th impeller requires the most frequent replacement, it's also the most likely to be the cause of most phantom overheats.

2) Telltale (pee hole): Just a hose that runs from the engine cooling system out the side of your motor compartment. Usually near the bottom starboard side of the engine compartment and you should be able to see a stream of water letting you know that the impeller is supplying sufficient pressure to water circulation system. IT SHOULD BE A CONSTANT HARD STEADY STREAM, not a limp steady stream. This does not come and go when thermostat cuts on and off.

3) Thermostat: If you have a good pee stream and you over heat then it's typically your thermostat I think. I forget the exact temp range, but the outside of your engine block shouldn't get much hotter than 175 F if your cooling system is functioning correctly.

The other main thing to check would be a blockage somewhere in your system, but if you have blockage then you'd likely see a difference in your telltale.

Good luck!

Just a note since you said you're new to outboards... you can run your motor on "ear muffs" in your driveway, but you shouldn't really run it in gear nor should you run it at anything over fast idle for more than a short rev. They need the resistance of the prop turning in the water and the back pressure on the exhaust system to avoid potential damage.

 

[wbpope]

Re: '86 70hp johnson overheated....

Thanks...I have not run her without water but, she did get VERY hot...even though in the water. I shut her down when I noticed some sounds I didn't recognize as "good"

I've not tried to start her since overheating...rowed a mile home..

I'll give it a try but, won't run her at all. See if she still has compression.

I found a site with some exploded views that were helpful...I'll share :

http://www.sterndrive.info/outboardmotor/i_need_help_page.html

Before I start breaking her down, is there anything that just might be doable from the top while she is still in the water? The thermostat I will remove until I fix the other problems, of course.

 

[wbpope]

Re: '86 70hp johnson overheated....

Quick update....We got the engine started with no difficulty at all. Compression seems good.
Let her idle for 20-30 seconds and cut her off before she got hot....no water from the pee hole at all.
Next, we haul her out and change the pump and thermostat...crossing our fingers, too.
Any other suggestions?