running without a t-stat

[opposedtwin]

Some years ago (maybe 8) I put a new t-stat in my 1959 lark (35 hp) and it has always pumped well. Today only a fine mist came out and then that disappeared and it only pump out hot air. The t-stat housing was too hot to keep my hand on so I shut iot down and removed the t-stat. Then it started pumping water like crazy. It ran good but with lots and lots of blue smoke (more than I remember from 2 years ago when I last ran it). I suppose it never warmed up enough to allow the rings to expand and seal up?

so is there any danger in running it without a t-stat until I can get one? I seem to recall a discussion about this topic a couple years ago but I don’t recall the specifics.

thanks!
scott

[rudderless]

Cya answer is never run without a thermostat.

Others will say outboards don’t need thermo’s.

Many outboards were designed without a thermostat.

If given the choice only between overheating or running too cold for a short of time I pick too cold.

Some models need the restriction of the thermo to flow the water properly through the motor. Some do not.

Its probably motor dependent on whether to run with or without for a short period of time.

I designed and made an external manually adjustable flow restrictor for my 9.9/15 instead of a thermostat. I can set it anywhere I want from the outside. I wasn’t sure if the cooling demand would follow the flow curve but it works terrific.

[wiscoboater]

Toss that Lark aside and bolt up your new Mark 30. Your welcome.

[fleetwin]

Maybe your thermostat is just stuck closed….
In any event, it’s not going to hurt anything to run it for a short time until you take a closer look at the pump/cooling system. I wouldn’t run it too fast though, just in case it overheats. Make sure your hot light/horn is working properly.

[chris-p]

If you are going to remove it for a short time, DO NOT remove the rest of the assembly beneath it. As in the housing/grommet, the spring and the valve (white plastic disc). Exhaust gas can get down to the pump via this route if the whole assembly is removed, allowing air(exhaust gas) into the water pump, rendering it useless.

Cannot tell you how many "No Water Pump" situations I have cured by installing a thermostat and assembly. Owners often think they are helping cool the motor by removing all of this, but really they are only making the matter worse.

[frankr]

I suspect the lake water up there in Wisconsin probably is about as warm as it will ever get—which is cold. Quite different than here in Florida where it gets up into the 90’s. Maybe we don’t need a thermostat as much as you do.

That Lark has a pretty sophisticated cooling system. For one thing, it has a quite large water pump. It is a thermostat-controlled, recirculating cooling system. When the stat is closed, the water returns to the pump for recirculation. When the stat decides it is warm enough, it opens and discharges some water, which is replaced by lake water. This goes on all the time it is running, the stat constantly sampling the water and opening or closing as necessary to maintain as close to optimum temp as possible. That actually is like your car, except it uses lake water instead of radiator water.

[chris-p]

quote wannabe outboard guy:

Toss that Lark aside and bolt up your new Mark 30. Your welcome.

He doesn’t need a sacrificial anode, he needs a motor.

Sorry, couldn’t help myself, kidding of course.

[wiscoboater]

quote Chris_P:

quote wannabe outboard guy:

Toss that Lark aside and bolt up your new Mark 30. Your welcome.

He doesn’t need a sacrificial anode, he needs a motor.

Sorry, couldn’t help myself, kidding of course.

59 Lark. 30hp motor? So heavy it takes 15 to push it through the water. Makes a better mailbox. 🙂
Chris, do you still have those other Merc starters? Shoot me a Pm if you do. I don’t want to hijack Scott’s thread here.

[1946zephyr]

Nothing wrong with a Lark. One of the most reliable motors ever built. I just woke up my RDSL-21B and it sprang to life in a couple minutes and it sat idle for about 5 years. LOL Big Twin OMC’s rock!

Yes! Get T stat in that and you’ll be good to go 😀

[beerman57]

If you run in cold water you need it. I’m in Florida and take t-stats out of small motors, but you do need to restrict the water flow some, so use a t-stat grommet and get a stainless steel washer that fits inside.

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