2000 90hp Johnson/thermostat

Roberthill

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They say there is no dumb questions ,here goes , What will happen if I remove thermostats and run without them ?
 

oldcatamount

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Re: 2000 90hp Johnson/thermostat

Removing the t-stats will cause the motor to run too cold and result in poor combustion, plug fouling, and dropped compression. Not advisable to run without t-stats.
 

Roberthill

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Dec 3, 2012
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Re: 2000 90hp Johnson/thermostat

I'm thankful for your reply . Water temperature around here gets to about 60 degrees during winter and around 90 in summer , do you think this might make a difference?
 

Faztbullet

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Re: 2000 90hp Johnson/thermostat

It will also not come out of Quickstart, you will have to rev it up several times to get it to come out....
 

rothfm

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Re: 2000 90hp Johnson/thermostat

Yes on all the above, not running at proper engineered tempature will causes in the form of carbon, and you chance fouling the rings and breaking one or more. Others do it, but those that know better do NOT recommend it.
 

V153

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Re: 2000 90hp Johnson/thermostat

In my neck of the woods alotta guys do not run thermostats on those kinda motors. Myself included. The Tstat housing is such a pita to get at that you will never ever wanna have to go in there again!

But you do need to restrict the flow. Some folks use ss fender washers, bleve it's the 1/4" ones that fit into the manifold perfectly. Others nip the guts off the origional thermostats & reuse just the flange.

If that Johnson is anything like my '83 & '86. It has spring loaded restrictors next to the tstats that are controlled by engine rpm. Via your water pump. You do need to inspect the springs, nylon valves, and the rubber seals that they seat against in the manifold.

Not suggesting everyone should rush out'n remove their tstats, but I have it on purty good authority doing so won't cause any ill effects. If you do run tstats on these motors it is imperative that you keep your impeller up to date. I have seen more than one occasion where a chunk of impeller got lodged in the tstat spring, preventing it from fully opening, and causing the motor to overheat.
 

Faztbullet

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Re: 2000 90hp Johnson/thermostat

The Tstat housing is such a pita to get at that you will never ever wanna have to go in there again!
This is a looper ..not a crossflow and t-stat's are easy to access.
But you do need to restrict the flow. Some folks use ss fender washers, bleve it's the 1/4" ones that fit into the manifold perfectly. Others nip the guts off the origional thermostats & reuse just the flange.I have it on purty good authority doing so won't cause any ill effects.
This is a old racers trick and is good for high speed use only. Not using t-stat will cause a engine to run cold, rich at idle, incomplete combustion leading to carbon build up, ring breakage from ring land cabon, cold seizing of piston if water to cold and engine hammered right off trailer as piston expands faster than cylinder. If engine didnt need them factory would have installed them.......
 

V153

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Re: 2000 90hp Johnson/thermostat

This is a looper ..not a crossflow and t-stat's are easy to access.

This is a old racers trick and is good for high speed use only. Not using t-stat will cause a engine to run cold, rich at idle, incomplete combustion leading to carbon build up, ring breakage from ring land cabon, cold seizing of piston if water to cold and engine hammered right off trailer as piston expands faster than cylinder. If engine didnt need them factory would have installed them.......
Like I said, don't everyone rush out & remove their Tstats, 'specially if they run in cold water.

However: I ran a '86 90hp, sans tstats, from '06 til it blew a head gasket just a few months ago. Motor was run hard but also spent it's fair share of time idling through our beloved Manatee zones. Upon disassembly it showed none of the symptoms/problems you mentioned. Very lil carbon build up, etc. Head gasket failed as a result of water jacket eroding from cyl wall/sleeve. Even though this motor was flushed religiously after every use, the saltwater still takes it's toll. Just a question of time.

But I digress. Never tried to suggest running w/o tstats is for everyone. But those who run 2 strokes in warmer water shoudn't experience any problems.
 

bob johnson

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Feb 25, 2009
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Re: 2000 90hp Johnson/thermostat

I have tried to experiment with thermostats to find a cause of a hot cylinder. I found that if you remove both thermostats your water pressure drops like a rock..... maybe its not a bad thing because the engine is getting cooled very well....i have a motor similar to the OPs and what ever you do, dont remove only ONE....all the water will head towards the open chamber and very little will go to the head with the Tstat still in it...so that head will really run hot.

I have been looking to replace my tstats. they are the hard plastic enclosed kind.....they actually have a standard looking tstats inside


but i have only found one that say they are 143 degrees....... although most of the time the seller doesnt say anything about the temperature they open at.....do tey make different temperature opening tstats in that style( for the 60 degree looper motors)

bob
 

Faztbullet

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Re: 2000 90hp Johnson/thermostat

Hey Bob..... you can use the 437090 as its a 133? degree if you can get them apart....
 

bob johnson

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Feb 25, 2009
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Re: 2000 90hp Johnson/thermostat

Hey Bob..... you can use the 437090 as its a 133? degree if you can get them apart....

are you saying I can use JUST the tstat from that motor with out the sleeve and gasket?

it will seal against the rubber seat on my head????

and NOT slid off the spring under 30 psi of water pressure...

the plastic body Tstat in my motor now , it seems can back off the seat and not fall off the spring because the nose is tapered and still inside the ID of the seat.....

my tstats were opening in a pan on the stove at about 155 degrees!!

thanks for the help

bob
 
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