Can I run my 25 hp johnson without the thermostat?

[csgrizz]

Hey guys, I have a 1977 johnson 25 hp electric start.

Just took it to the local boat guy because it was getting hot.

He told me the thermo was stuck and not allowing the engine to cool, its pumping good, but the water isn't getting where it needs to go.

He removed it but didn't have one in stock.

Here's the kicker, I leave for vacation on the lake in the morning. He said it would be fine until I get back to run it without the thermo.

Is this true? I am not in a position where I can replace a motor so I would rather sit on shore all week than chance it?

Hopefully someone has a chance to get back to me before the morning.

Thanks in advance,

CS

 

[joho5]

Re: Can I run my 25 hp johnson without the thermostat?

from what I have read on this issue I dont think it would be a problem for a short period of time to do that. The thermo is there to allow the motor to maintain a constant temperature that suits the life of the motor and how it performs.

Your motor is supposed to run at a certain temperature and goes along with spark, compression, and carbeuration, etc...your motor will run without it, but for the life of the motor you wouldnt want to do it for an extended period of time.

There might be someone that can explain this better than me.

 

[tashasdaddy]

Re: Can I run my 25 hp johnson without the thermostat?

for a week fine, then replace the tstat, it will idle badly, be harder to start, also may foul the plugs easier. but it will run.

 

[scrampbell]

Re: Can I run my 25 hp johnson without the thermostat?

So without the thermostat will it constantly circulate water for cooling (i.e. it will run cool) or will it never kick in the cooling (i.e. run hot)?

Is there a way to short/break the circuit to get the opposite behavior? I'm assuming that running cool is preferable, right?

 

[csgrizz]

Re: Can I run my 25 hp johnson without the thermostat?

Hey guys thanks for the quick replys. I took it to the local lake, and it ran just fine and stayed cool. Thermo is on the way but it won't be here till after I leave today.

I appreciate the posts, thanks again,

CS

 

[Silvertip]

Re: Can I run my 25 hp johnson without the thermostat?

There is an issue called "cold seizing" which can occur because the pistons heat up quicker than the cylinder -- sort of the opposite of an overheat seize. This can occur if you do not allow the engine to warm up sufficiently before you go full throttle. Without the stat, water flows full force through the engine so the chance of overheating is low if everything else is ok. Poor idle, more smoke, as mentioned may occur. Just don't hammer down a stone cold engine.