1984 70 hp johnsoh question

[G dog]

Hello everyone. I have a thermostat question hopefully someone can answer. I have a 1984 70 hp. J70ELOCRD. I just bought the boat a few weeks ago. When I started the engine it got hot right away.So I shut it down and pulled the thermostat. There was corrosion inside the housing and the thermostat was no good. I tested it in a pot of boiling water. I cleaned everything and replaced it with a new kit. Started the engine and it pees fine but the thermostat housing gets pretty hot. I can keep my hand on it for about 3 seconds and that is about it. I ran the engine for over 15 minutes and it did not get any hotter. The thermostat is a 143 degree thermostat. For the hell of it I took the thermostat out and ran it and it was very cold.(tested the new on and it opened fine) My question is, once the thermostat opens up shouldn't the temp be the same as when I took it out? or am I not understanding something. Also is my engine running hot? I am dying to take it out on a run but I do not want to blow my engine

 

[G dog]

There is got to be someone out there that can help me.

 

[racerone]

The first thing to do on any " new to you motor " is to install a new impeller in the cooling pump !!

 

[G dog]

Yes. impeller is new and has a very strong stream of water coming out

 

[racerone]

I guess I missed the new impeller in post #1 then.

 

[flyingscott]

Get a temp gun and check it we have no idea if your temp is good or not.

 

[G dog]

I went down this afternoon and bought one. We will see. Thank you

 

[oldboat1]

Guessing, but it sounds like the t.stat is opening properly, but the bypass is blocked. When you test temps, do it at the top of the cylinder head. If it's too hot to touch, the motor is running too hot. You need to test cooling systems in a barrel or in the lake -- muffs will not tell the story.

 

[G dog]

ok, temp at the top of the head varies from 162 to 165 degs. That is with the muffs on. I will try in the trash can and see what I get. Thank you for your help

 

[oldboat1]

that would be too hot. Look for 130-140. 160 is overheating.

 

[G dog]

in the trash can it runs about the same temp. give or take a deg. or 2. Im going to pull the lower unit and the thermostat housing and run the hose up it. maybe something blocking will come loose. Otherwise pull the head cover and head? or is there something else I could try first?

 

[oldboat1]

Sounds right. Do the easiest first. Include the exhaust manifold on the list.

 

[G dog]

I pulled the thermostat cover back off and there was some brown flakes hanging out in there. Im not even going to try and flush it. I ordered a gasket set and I am going for it all. You said to replace the manifold gasket wile I was at it. Do I use some kind of gasket sealer for the manifold and head or do I just set them dry and tork them to specs. If I use sealer what do you recommend? I found the whole powerhead gasket set on ebay for 58 bucks. I figure I might as well get the whole set since the engine is new to me and not really sure what to expect next.

 

[oldboat1]

I use OMC gasket sealer for most applications, or Permatex (#5?). Don't use silicon sealer. Your motor likely has a stainless plate in the exhaust manifold. Check that for warping.

Resurface exhaust and head covers with 400 grit wet/dry sandpaper, moving mating surfaces around in figure eight fashion until all surfaces are shiny.

 

[jakedaawg]

When you get it back together, with the lower still off, put water hose in the t stat housing and flush out through the water tube.

 

[G dog]

I got done with work early today so I decided to pull the head. Some of the passages are blocked with a thick light brown flaky paper like corrosion. And were it is not blocking the passages it coats the entire head cover and head about 1/16 to 1/8 plus thick.When I pealed the gaskets off it looked like there was still a gasket on there. I scraped what I could off but not even close to clean. is there a product out there that I can soak it in to break it up? I was thinking some kind of acid solution but Im not sure if it will damage the metal.Ok, that is problem number one. The second problem is that the very last bolt to remove snapped in the head. Yes, the very last one! And we all know were that one is. There is about a 1/4 inch of bolt sticking out so there is something to grab on to. Does anyone have a good trick to get it out? I have it sprayed down with PB and letting it set over night. Oldboat1 suggested I change the manifold gasket but that scares me now.

 

[Dennischaves]

A little heat and vice grips will get the bolt out
sometimes you can get away with just vicegrips and pb blaster
​​​​​​

 

[G dog]

ok, I pulled the powerhead off to get to the broken bolt. Drilled and tapped it and replaced head gasket and manifold gasket. Reintalled the power head and fired it up. still the same problem. runs like a champ but gets hot. I pulled the thermostat and it was not open. then I put it in hot water and it opened. ( new thermostat) It doesn't seam to be getting water were the thermostat is. it appears to be dry inside the housing. Could someone give me the run down on how the pressure relieve valve operates? When I pulled the housing it was wet where the springs and valve is but not behind the thermostat. Maybe I have a problem there? I ran it again without the thermostat and it ran nice and cool. I forgot to mention that I cleaned all the passages and blew compressed air threw everything. Another thing that is happening is it wont shut down when I turn the key off. Nor will it die when I pull the kill switch cord. everything worked before I started this mission. The thing is I didn't really have to disconnect any wires exept the battery and harness. Any and all help would be appreciated.