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From: ben91932 on 8 Feb 2010 11:09
On Feb 4, 5:15 pm, mark <markha...(a)hotmail.com> wrote:
> I am building an airboat and have an old 350 chev. in it.

If it were me, I'd run the engine closer to 180.
Summitt or Jeggs or Gale Banks should carry the switch...

HTH,
Ben
From: mark on 11 Feb 2010 14:48
On Feb 8, 12:09 pm, ben91932 <benteac...(a)gmail.com> wrote:
> On Feb 4, 5:15 pm, mark <markha...(a)hotmail.com> wrote:
>
> > I am building an airboat and have an old 350 chev. in it.
>
> If it were me, I'd run the engine closer to 180.
> Summitt or Jeggs or Gale Banks should carry the switch...
>
> HTH,
> Ben
It is still not right. Today we ran the engine and it climbed to
around 195 and stayed for a few minutes and then climbed to ~230
before the fan turned on. The fan runs until it is back down to ~200.
If the engine sits there idling it will continually climb to 230, fan
on ,cool to 195-200 and the fan shuts off and the climbs back to
230....Shouldn't the switch be rated at the same temp. as the the
thermostat. It doesn't make sence to have the radiator water hotter
than what the thermostat lets out.
From: jim on 11 Feb 2010 19:45


mark wrote:
>
> On Feb 8, 12:09 pm, ben91932 <benteac...(a)gmail.com> wrote:
> > On Feb 4, 5:15 pm, mark <markha...(a)hotmail.com> wrote:
> >
> > > I am building an airboat and have an old 350 chev. in it.
> >
> > If it were me, I'd run the engine closer to 180.
> > Summitt or Jeggs or Gale Banks should carry the switch...
> >
> > HTH,
> > Ben
> It is still not right. Today we ran the engine and it climbed to
> around 195 and stayed for a few minutes and then climbed to ~230
> before the fan turned on. The fan runs until it is back down to ~200.
> If the engine sits there idling it will continually climb to 230, fan
> on ,cool to 195-200 and the fan shuts off and the climbs back to
> 230....Shouldn't the switch be rated at the same temp. as the the
> thermostat. It doesn't make sence to have the radiator water hotter
> than what the thermostat lets out.

Maybe it could be a little lower. It would be nice if it would come on
at 220F and go off at 195F. The important point is you have proven the
fan can cool it down fairly quickly. You didn't say whether the engine
cooling system has any naturally moving air through it or if you are
just test running it stationary.

The span of temperature and delay you are seeing in this switch is
going to be still there with a colder switch. So if you get a switch
that kicks on at say 210F instead of 230F then it will turn off that
much lower also, which in your case would be something below 195F. that
means the thermostat will start to close to try keep the temp from going
below 195F and the fan will run much longer (or maybe not shut off at
all) because it will be working against the thermostat.
Ideally in operation you should have airflow through the radiator and
the fan should only be needed when idling or moving very slow.

-jim
From: mark on 11 Feb 2010 20:26
On Feb 11, 8:45 pm, jim <"sjedgingN0Sp"@m(a)mwt,net> wrote:
> mark wrote:
>
> > On Feb 8, 12:09 pm, ben91932 <benteac...(a)gmail.com> wrote:
> > > On Feb 4, 5:15 pm, mark <markha...(a)hotmail.com> wrote:
>
> > > > I am building an airboat and have an old 350 chev. in it.
>
> > > If it were me, I'd run the engine closer to 180.
> > > Summitt or Jeggs or Gale Banks should carry the switch...
>
> > > HTH,
> > > Ben
> > It is still not right. Today we ran the engine and it climbed to
> > around 195 and stayed for a few minutes and then climbed to ~230
> > before the fan turned on. The fan runs until it is back down to ~200.
> > If the engine sits there idling it will continually climb to 230, fan
> > on ,cool to 195-200 and the fan shuts off and the climbs back to
> > 230....Shouldn't the switch be rated at the same temp. as the the
> > thermostat. It doesn't make sence to have the radiator water hotter
> > than what the thermostat lets out.
>
> Maybe it could be a little lower. It would be nice if it would come on
> at 220F and go off at 195F.  The important point is you have proven the
> fan can cool it down fairly quickly. You didn't say whether the engine
> cooling system has any naturally moving air through it or if you are
> just test running it stationary.
>
>         The span of temperature and delay you are seeing in this switch is
> going to be still there with a colder switch. So if you get a switch
> that kicks on at say  210F instead of 230F then it will turn off that
> much lower also, which in your case would be something below 195F. that
> means the thermostat will start to close to try keep the temp from going
> below 195F and the fan will run much longer (or maybe not shut off at
> all) because it will be working against the thermostat.
>         Ideally in operation you should have airflow through the radiator and
> the fan should only be needed when idling or moving very slow.
>
> -jim- Hide quoted text -
>
> - Show quoted text -

The engine (airboat) is stationary right now, in a garage. I just find
it odd that the gauge is always cycling between 195 and 230, shouldn't
it just get up to 195 and stay there, the same way my truck does? I
tried running the Fan constantly and the gauge stays at 195.
From: jim on 11 Feb 2010 22:40


mark wrote:
>
> On Feb 11, 8:45 pm, jim <"sjedgingN0Sp"@m(a)mwt,net> wrote:
> > mark wrote:
> >
> > > On Feb 8, 12:09 pm, ben91932 <benteac...(a)gmail.com> wrote:
> > > > On Feb 4, 5:15 pm, mark <markha...(a)hotmail.com> wrote:
> >
> > > > > I am building an airboat and have an old 350 chev. in it.
> >
> > > > If it were me, I'd run the engine closer to 180.
> > > > Summitt or Jeggs or Gale Banks should carry the switch...
> >
> > > > HTH,
> > > > Ben
> > > It is still not right. Today we ran the engine and it climbed to
> > > around 195 and stayed for a few minutes and then climbed to ~230
> > > before the fan turned on. The fan runs until it is back down to ~200.
> > > If the engine sits there idling it will continually climb to 230, fan
> > > on ,cool to 195-200 and the fan shuts off and the climbs back to
> > > 230....Shouldn't the switch be rated at the same temp. as the the
> > > thermostat. It doesn't make sence to have the radiator water hotter
> > > than what the thermostat lets out.
> >
> > Maybe it could be a little lower. It would be nice if it would come on
> > at 220F and go off at 195F. The important point is you have proven the
> > fan can cool it down fairly quickly. You didn't say whether the engine
> > cooling system has any naturally moving air through it or if you are
> > just test running it stationary.
> >
> > The span of temperature and delay you are seeing in this switch is
> > going to be still there with a colder switch. So if you get a switch
> > that kicks on at say 210F instead of 230F then it will turn off that
> > much lower also, which in your case would be something below 195F. that
> > means the thermostat will start to close to try keep the temp from going
> > below 195F and the fan will run much longer (or maybe not shut off at
> > all) because it will be working against the thermostat.
> > Ideally in operation you should have airflow through the radiator and
> > the fan should only be needed when idling or moving very slow.
> >
> > -jim- Hide quoted text -
> >
> > - Show quoted text -
>
> The engine (airboat) is stationary right now, in a garage. I just find
> it odd that the gauge is always cycling between 195 and 230, shouldn't
> it just get up to 195 and stay there, the same way my truck does? I
> tried running the Fan constantly and the gauge stays at 195.

It stays near 195 because the thermostat will restrict the flow and
hold the temperature. that was my point if you get switch that turns off
below 195F then once it comes on it will run constantly.


On many vehicles that have a temp gauge the gauge is designed to not
move much in the normal operating range so you don't observe the
fluctuating when the fan goes on and off. The needle on the gauge moves
quite a bit from something like 150-190 and then it moves very little
from 190-220 and if the temp gets above 220 the needle starts to move
upward pretty quickly.
You are going to need a more sophisticated control system than a switch
with a single upper and lower limit. You don't want it so the fan comes
on for 5 seconds and off for five seconds - on and off constantly. That
isn't good for longevity of the switch or fan.
If there good flow of air when the airboat is moving it may not need
the fan except when it is idling. If you can get a switch that turns off
at exactly 195 it may run constantly at idle but once you get moving the
extra cooling may drop the temp enough to shut it off.


-jim
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