Thermostat issue.

[NEWORLEANS-YAT]

I let my motor idle for 6 to 7 min. and the head never even warmed up. Can this cause the motor to run rich and foul plugs. I put my fingers on the head and it was ice cold.

Thermostat must be stuck open.

Its a 1986 Johnson 28 SPL.

 

[Joe Reeves]

Re: Thermostat issue.

Yes, if the thermostat exists, I'd agree that it must be stuck open. Replace it. However, I've never heard of that problem causing plug fouling... possible, I"ve just never encountered that problem.

(Thermostat Purpose)
(J. Reeves)

Many engines are considered high performance engines and demand a thermostat(s), and many smaller hp engines also require a thermostat for the following reason. The pistons actually distort/twist off round when running. The thermostat is required to keep the outer wall surrounding the steel cylinder, and the cylinder wall itself at a temperture to compensate for the distortion.

With the thermostat removed, the difference in temperture between the inside the cylinder and the water jacket quickly reaches a point whereas (in effect) you have a oblong piston running up and down a round cylinder, or vice versa. Bottom line is without the thermostat, the piston and cylinder wall could be damaged in a short period of time.

The thermostat in your car isn't there simply to have the heater function properly..... think about it.

 

[NEWORLEANS-YAT]

Re: Thermostat issue.

Thanks for the info. Where can I find directions to change it out?

Thanks again

 

[mortymolly]

Re: Thermostat issue.

Here is a great tip...put a quart of white vinager in the microwave for about 4doing mins...drop the t stat in and stand back...it will fizzle ...that will be all the contaminates discharging...also you be able to tellif it opens and closes...and it may save you grom buying a new one...mine is forty bucks new

 

[Haffiman]

Re: Thermostat issue.

Thanks for the info. Where can I find directions to change it out?

Thanks again

Remove the cover on top of the cylinder head. Be aware that the screws between the cylinders (in center) breaks easily, use some heat.

 

[F_R]

Re: Thermostat issue.

The thermostat on that motor is a joke. It has a pressure relief spring holding it in position. High water pressure is supposed to unseat it and provide extra cooling at high speed. Trouble is, it unseats at low speed too, and the thermostat does virtually nothing.

Besides that, there is so much intentional water bypass through another flow route that it never really warms up anyway.

Mine has never really warmed up since the day I took it out of the shipping box. And yes, I have removed the head cover and inspected the thermostat. And yes, the plugs do get very crappy from lots of idleing. Know what? The CD ignition fires them anyway. It really isn't a problem.

 

[NEWORLEANS-YAT]

Re: Thermostat issue.

Thanks for that info guys. I pulled it out yesterday and changed it. It was the original one since 86. After running it for 7 min it got warmer than it did before i changed it. Even after the new stat the plugs still got crappy like F_R said.

Water pump and fuel pump next.


Thanks again yall

 

[F_R]

Re: Thermostat issue.

The plugs in my motor. It starts and runs perfectly, never misses a beat, will idle all day.

 

[NEWORLEANS-YAT]

Re: Thermostat issue.

Wow. Mine were alittle wet with oil. When I lock my motor in the upright position I get about a table spoon of fuel/oil mix leaking out the large air inlet of the carb. Is that normal?

 

[Haffiman]

Re: Thermostat issue.

If the plugs get black from soot, it runs rich. However if getting 'wet', somewhat like the ones on the pick from F_R, the engine might in fact run lean!!
Try either to 'play' a little with the timing advance (synch), or adjust the idle mix screw slightly richer.

 

[NEWORLEANS-YAT]

Re: Thermostat issue.

I did a resetting of the low speed jet last night. I need to run it and check the plugs.

Thanks

 

[toddschubert]

Re: Thermostat issue.

Put it together and cross lake ponchartrain and back at wot and it will be all cleared up. lol my fellow yat. Something about those motors sure is spl.

 

[NEWORLEANS-YAT]

Re: Thermostat issue.

The plugs in my motor. It starts and runs perfectly, never misses a beat, will idle all day.

should i run Champions and get rid of the NGK's ?