'77 Johnjon 55 cooling problem.

[4speedfury]

Hello everyone! I just bought a small boat with the 55 on it. I ran it today with the muffs on the lower unit where the steel mesh is covering the holes. It fired right up and ran super, but it did get too hot for my liking, so I shut it down after about 1-1 1/2 minutes. There was a stream of water coming out of a small hole in the front of the lower unit as well as a good amount of water coming out of the holes in the side of the lower unit above the cavitation plate. I'm not sure where to look. I was told the seals and water pump were replaced 3 years ago and it was not run since. Is it possible that I simply did not have enough water pressure going when I was running it? I was afraid of blowing seals in there somewhere as I get a lot of pressure from my well. What else should I look for?
Thank you for reading my rant.

 

[Joe Reeves]

Re: '77 Johnjon 55 cooling problem.

Those small holes just above and to the rear of the cavitation plate are the outlets for water when the thermostat(s) open.

On a engine that size, running on a flushette, the water must be on full blast. This full blast amount would be the normal house pressure so figure accordingly comparing your well pressure to city supplied pressure.

Try it again with the water on in this manner, then let us know what you find.

Note that the engine has a hot horn warning feature and will sound off in a steady constant beeping before the engine gets hot enough to do any damage.

(Testing Warning Horn)
(J. Reeves)

On VRO equipped engines where the VRO automatic fuel/oil setup is still being used, make sure that all components are connected as required. This would include the VRO pump wiring harness itself, the oil tank wiring, the overheat sensor(s), and if so equipped.... the vacuum switch that is standard to many V6 & V8 engines.

If the VRO automatic setup has been eliminated and has been disconnected properly, and the fuel and oil is being premixed, make sure that the overheat sensors are still connected, and the vacuum switch if the engine is so equipped.

On engines prior to 1984 which have no VRO setup, ignore the instructions pertaining to the VRO components, etc above.

Turn the key to the ON position (Engine Not Running). Find the TAN wire at the cylinder head(s), then ground out the portion of that wire that is part of the engine wiring harness. If that Tan wire connector has the knife type connector where as it is exposed simply by sliding the rubber insulator back, it does not need to be disconnected.

Grounding that TAN wire should cause the horn to sound. If it does not, find out why as that's the only warning you'll receive should the engine overheat or have some portion of the VRO system fail, or have the engine encounter a fuel retsriction if it is equipped with a vacuum switch.

 

[4speedfury]

Re: '77 Johnjon 55 cooling problem.

Thanks Admiral Reeves!
I just got back in from running it again. Same problem. I didn't have a chance to check the horn. The engine got to hot for me to touch the cylinders for more than a second before it started to hurt. Does this engine have a thermostat?
Thanks again.

 

[HighTrim]

Re: '77 Johnjon 55 cooling problem.

I would imagine that after sitting for 3 years, that impeller has bit the bullet. Drop the lower unit and change it. It will be cheap , but if it fails will cause alot of damage. Would also get a t stat and gasket and change that as well.

 

[EJ3]

Re: '77 Johnjon 55 cooling problem.

I believe we have the same engine. I have been told it has a Tstat. I have also heard that most of the time when a Tstat gets stuck it gets stuck open. I am working on my motor right now since I just got it so I am not real familiar with it yet, and definetly not an expert. To test your temp warning horn ground the wire coming out right above and to the left of your top spark plug. I just poked a nail through the wire and into the block behind it. Ofcourse make sure your key is in the on position.

 

[4speedfury]

Re: '77 Johnjon 55 cooling problem.

Thanks to all for all of the input. Please let me know where the t-stat is when you figure it out. Oh, and the horn works. I nearly messed myself when it went off while testing it. I thinkI'll take the lower unit off and change the impeller. At any rate it's cheap insurance. And besides, I want to check all of the passages anyway.

 

[HighTrim]

Re: '77 Johnjon 55 cooling problem.

Here is your t stat. Number 12 on the diagram.

 

[samo_ott]

Re: '77 Johnjon 55 cooling problem.

HighTrim, that photo looks like a micro dot! Got a bigger pic?

 

[Joe Reeves]

Re: '77 Johnjon 55 cooling problem.

There is a plate covering the cylinder head. The thermostat is under it. Remove the plate to access it.

 

[HighTrim]

Re: '77 Johnjon 55 cooling problem.

oops sorry, lol. What? You cant see that Samo?? 4 speed go to the BRP webpage to access the parts diagram if you still cant find it. Here is a link, just click on "Find Evinrude Engine Diagrams, then "View Parts Catalogue", then top left corner, Johnson, the GO, input your year, hp, model number, etc...

"http://www.evinrude.com/en-CA/Accessories/Literature/?popup=true"