1984 Johnson 175 hp Seahorse

[rabbi]

Is it Okay to run this motor without thermostats? I've talked to 6 mechanics - 5 say "Yes, it's Okay" - 1 warns me that it will make the motor run sluggishly and foul the plugs faster. Any ideas?

 

[OBJ]

Re: 1984 Johnson 175 hp Seahorse

Rabbi....DO NOT run the engine without t-stats. Do so only in an emergency to get home. Engines are designed to run at a certain temp or range. This temp contributes to the combustion process and block expansion. <br /><br />You risk cold siezing of the engine if run without the stats. And yes, the engine will idle poorly and combustion will not be great as the one mechanic pointed out.

 

[rabbi]

Re: 1984 Johnson 175 hp Seahorse

The four mechanics that said it was OK, said the reason was the motor was an older model (1983) and only the new models require stats to maintain a proper operating temp. Any truth to this?

 

[ob15]

Re: 1984 Johnson 175 hp Seahorse

No truth. Use a T-stat.

 

[duke3]

Re: 1984 Johnson 175 hp Seahorse

No truth, always use a thermostat.<br />If running without thermostat, the motor will then work at too low temp.<br />That meens the clearens between cyl wall and piston is always too big, and the piston rings, will also have too big clearens.<br />This will give you more dust and sod when the motor is running. And after a while, there will be too mutch dust and sod around the piston rings, whitch will give you lower compression pressure. And in the end the motor will not start.

 

[Joe Reeves]

Re: 1984 Johnson 175 hp Seahorse

Rabbi.... The four "Mechanics" that told you that you could run that engine without thermostats have no technical knowledge of the thermostats purpose.<br /><br />When running, the inside temperture of the cylinder effecting the steel sleeves and the piston actually cause a distortion, which in turn causes a distortion difference between the piston and sleeve. What this means in laymans terms is that the piston no longer fits the cylinder perfectly.<br /><br />The thermostats are set to open at approximately 143° or 148°, effectively keeping the water surrounding the outside of the cylinder walls to a temperture determined by knowledgeable engineers to compensate for the distortion mentioned above which returns the piston and cylinder wall to a matched fit.<br /><br />Bottom line.... run without thermostats, and in time you'll have some mighty scored pistons and cylinder walls. Something to think about... the thermostat in your vehicles aren't just to supply hot water to the heater. There's another purpose. Guess what it is (grin).

 

[rabbi]

Re: 1984 Johnson 175 hp Seahorse

As far as I know, this motor has been running without stats for a couple of years before I bought it - the compression on each cylinder was between 110 and 112 on all 6. There seems to be a center hole on the thermostat housing that has been sealed with JB Weld or something - If I decide to put stats back in this, how do I go about it?

 

[wilde1j]

Re: 1984 Johnson 175 hp Seahorse

Well, you've found five mechanics to avoid, and so easily! Good work.<br /><br />Regarding replacement of the stats, look at BRP's website ... they have exploded parts lists. It should be obvious.

 

[Steve135]

Re: 1984 Johnson 175 hp Seahorse

The JB weld was use to fill in the hole that the T-stats block. If the T- stats were in place the water wouldn't leak out. Just drill them out . The same size as they once were. If you can't measure them from the inside. Measure someones elses.

 

[wild tripp]

Re: 1984 Johnson 175 hp Seahorse

Could someone give me a little information??
I am in the process of installing a 1985 Johnson 175 hp engine on a 24 foot pontoon and am having a problem with the ignition switch. It seems as though when I have the switch mounted at about a 45 degree angle facing up the switch will not start the engine. However hold the switch level or facing up straight . the darn thing will engage the starter. I have tried two switches and they both do the same thing. One is new and other used???
Any help would be greatly apprec... thanks Harold..

 

[tx1961whaler]

Re: 1984 Johnson 175 hp Seahorse

Most likely an internally broken wire that makes contact when it's twisted around. ALso, PLEASE don't resurrect a 3+ year old thread. Start a new one.