1983 Johnson 70 hp water issue?

[ArrowNaughtic]

Johnson 70 hp J70ELCTE
Started up motor on the muffs so I could warm up lower unit a little to change oil. When first started got a great tell tale stream running. As it warmed up tell tale slowed down considerably and water coming out was getting almost too hot to hold my hand under the stream. I shut the motor off and looked up a new impeller and thermostat.Will buy one or both if needed.
Question is: Do I need to replace thermostat? Is there a easy method to back-flushing the water jackets to rule out a clog somewhere? As soon as I get parts I will pull LU and change impeller and also thermostat if needed and new seal for it.
Is back-flushing a good idea with thermostat out?

 

[gm280]

Your engine is 34 years old. With that stated, there could be possibilities of build up in the water passages. But that remains to be seen without pulling the power head down. I would replace both the thermostat and impeller first and see how that goes. Here is something to think about.

When you first started the engine, you had a good stream of water coming out. So that seems like the build up would have effected the initial start as well if it was a blockage. The Thermostat could not be operating right and causing the water to remain in the block longer then usual. But that is all merely guess work there.

Replace those parts and see what you have as a first effort. And I would flush water through the water tube by the impellor and where the thermostat installs as well. And even from the outlet if you can. But with the thermostat and the impellor removed as well. JMHO

 

[racerone]

Look at the 2 grommets and poppit valves when thermostat cover is off.-------Water from tell tale should not be hot !

 

[David Young]

I would buy the thermostat kit sold from this Forum. It has all the gaskets and the thermostat. 'If' your poppit valves are inside the thermostat cover like my 1977 Evinrude was, I would order new poppit valves (2 of them) and the rubber grommets also. If your 83 is like my 77

 

[racerone]

An 83 model uses the same thermostat / poppit valve parts as a 77 model.

 

[ArrowNaughtic]

Ok, will get parts and flush out as much as possible. This was not an issue last year when winterized so something must have broke loose when I fired it up this year. I will also pull the tell tale hose and backflush from there. Thanks for the knowledge and helpful advice!

 

[ArrowNaughtic]

Update: Went out and ran outboard again today with tell tale hose unplugged and draining over side of lower motor cowl. Saw some gunk when I first started motor and continued to let it run for almost 15 minutes. Good stream the entire time and no heat build up like before. My outlet hose inner diameter is bigger than the attachment through the motor cowl inner diameter. So something popped loose the first time I started up the motor this year and plugged the outlet keeping the water in the motor longer.
I will still change the impeller and thermostat before taking boat out for the first time this year. When I change them I will definitely back-flush the system and make sure I have a clean as I can get water cooling system. I was worried that I was going to have to tear the motor down and scrape all the water jackets. I think I dodged a bullet but am still not out of the woods. Will try to update after impeller and thermostat are changed.