1986 Johnson 70HP Thermostat Assembly

[Flak]

Hi folks.<br />I been browsing this forum for a while and it's been a great help. I'm just finishing up a complete power head rebuild of my father-in-laws 86 Johnson 70HP S/N J70ELCD. One problem I have is the person who worked on this motor last replaced the head, but never installed the thermostat. I have the new stat seal, and a new stat, but something isn't quite right. The manual I have shows an exploded diagram of the stat assy, but I think the diagram is for an older model. I'm pretty sure this particular model requires a spring as well. As far as I can tell, the seal goes in the bottom of the stat port in the head, then the stat, then I'm assuming the missing spring, and then the cover. Can anyone confirm this for me, or possibly send me a diagram of this particular model? I really don't want to run the new motor without the stat, as I've read here they tend to run cold without one. My father-in-law has spent quite a few bucks, and I've invested quite a few hours in this motor, and I want to make sure I do everything right. <br /><br />Thanks in advance!

 

[mikeyzx2]

Re: 1986 Johnson 70HP Thermostat Assembly

Well the only diagram I have shows the thermostat housing at the top of cylinder head, with the seal going in first, then the thermostat, in the upper portion of housing. In the bottom portion the pressure relief valve assembly is installed, which includes the spring. The spring is not installed on thermostat itself in the diagram.

 

[Flak]

Re: 1986 Johnson 70HP Thermostat Assembly

Thanks for the reply. That's the same diagram I have, but it doesn't match this block. I have no pressure relief valve. I'll take a few pics and post them.

 

[mikeyzx2]

Re: 1986 Johnson 70HP Thermostat Assembly

that would help alot in figuring it out. my 1985 8hp has the stat in the top of head, and the way it's installed is the seal, thermostat, then spring. we'll help get it figured out

 

[Flak]

Re: 1986 Johnson 70HP Thermostat Assembly

Here's the stat housing buttoned up<br />Opened<br />Cover, stat and seal<br /><br /><br />Here's what number 2 looked like when I cracked it open.<br />Cause of compression loss?<br /> Nah

 

[Flak]

Re: 1986 Johnson 70HP Thermostat Assembly

Anyone?

 

[Terry H]

Re: 1986 Johnson 70HP Thermostat Assembly

You are missing the spring and the housing for the seal. You need to find a parts dealer with the parts breakdown if possible. Chief

 

[Flak]

Re: 1986 Johnson 70HP Thermostat Assembly

Sorry I missed your response Chief. Thanks!<br />But I'm still having problems with this. It appears that the head was superceded by OMC, yet the nearest OMC dealer (45 mins away) cannot help since his book lists the original stat assembly which is different from mine. The parts diagrams at ishopmarine, the dealer and my manual show the same thing, yet it's incorrect for this head. If you look at this shot HERE it shows the typical assembly, but if you look at the pics of the head that I posted above, it's not the same thermostat housing. This is driving me nuts.<br /><br />The original head, which I still have is part number 329835-3. The replacement head which was bought by a boat mechanic 3 years ago when he (kinda ) rebuilt this motor is a 339288. The parts list shows 394380 as the original head. All have been superceded by 435977. I've searched both '85 and '87 70HP parts lists to see if it was an early or late model '86, but no luck so far. I need a way to search for the year/model by part number. Or, just tell my father-in-law needs to buy a new head for $225.