Do we need a themostat?

[aaron]

I have a SANTE 03 with the excalibur 330.
As the water temperature here is always about 25C and it is warm (hot) all year round, how important is a thermostat?

Reason why i am asking is because my engine runs hot and its becos of the themostat( i think its isnt opening , hence no water out thru the exhaust , no fresh water in to the impeller)

When i remove it, temperature stays low at idling.

Can i run the boat without it?

[Fonseca]

RE: Do we need a themostat?

I can't understand very well your problem.
Can you be more specific?
If you have no water coming from the exhaust, stop the boat now!
When you say your engine runs hot, how hot is it?
Do you have fresh water cooling?
Do you have the intake seacock (yelow handle, in the floor, between the engine and the transmission) wide open?
How many hours you have run the boat without water coming from the exhaust? and without water in the impeller? I don't think that keeping the boat runing in this conditions can be good to your pocket!
waiting for your answer!

[Rick]

RE: Do we need a themostat?

Instead of running without a thermostst I would run a 142 degree rather athan a 160. I ran a 66 chrysler 318m without 1 for years with no ill effect. Having said that there is a chance that the boats preformance will suffer because it never gets to temp. Also check to see if it is blocked by pieces of the impeller. This would cause the running hot problem and just removing the thermostat won't fix running hot from a bad impeller.

[h20skier]

You can run the boat without the t-stat, but I don't recommend this. The t-stat is in the motor to not only to help it warm up quicker, but just as important it’s in there to keep it running at the designed/engineered operating temp.

[NautiqueJeff]

Sure doesn't sound like a thermostat issue to me. Check that your thru-hull petcock for the cooling water is open, and that your impeller is in good shape. Be sure that all lines are clear, and that no air is getting into your cooling system.

[aaron]

Thanks for all yr replies, and i will be more elaborate.
Boat ran for afew hrs last week , everything good.Temp guage always at 161/ 162F.
Before starting the boat this morning, cleared the water filter,
didnt completely tighten it ( my mistake) , air must have gotten thru, started engine
and temperature shot up to 195F not too long therafter.So shut engine off.

Suspecting impeller failure, opened the water pump, impeller was fine.Just to be in the safe side, i replaced it with a new impeller.
Backed the boat to the water, started engine, and saw water filter ( now properly hand tightened) filling up ...which is a good sign.
Idled for afew minutes, checking on temp guage, and temp shot past 175F to 180+F.
Sensing something wrong, waited for engine to cool down (risers were hot to say the least)
30 mins later, decided to remove thermostat, primarily to check if there is proper water flow and any effect on temp guage.Idled for long enough(15+mins) and temp stayed around 110 to 120F
I suspect the thermo didnt open up to allow the water to exit thru the exhaust.

Hence leading to my question....whether we really need a thermostat.
Point is, i am not in the US,and can't buy such a thermo off the shelf and altho i get full factory support , i was wondering whether i cd live without the thermo.

[Flux]

I am of the understanding that water is constantly cycling through the cooling system and exiting through the exhaust. The thermostat only opens to allow cooling water to cycle into the heads as needed.

It may take a moment to get water exiting through the exhaust, but I am fairly certain there should be water coming out of the exhaust at all times regardless of engine temps.

I would replace the T-stat anyway, since you opened that up. The check all of the lines for blockage or air suck. Make sure the raw water pump is spinning.

My 02 has an input for a garden hose. We close the ball valve for raw water intake and turn the garden hose on when changing oil or starting it up on the trailer. Water should make it all the way through the system when the hose is on even without the engine running. Might be an easy way to check if you have a block in one of the lines.

[surroundsound64]

I bet you have some trash or other debris lodged in the impeller.

When I winterize my boat, or completely drain the water out of the intake lines, if I don't prime them again first, the impeller will not suck water water out of the lake, I have to start the boat and immediately get underway to about 20mph to get water flowing. It was my understanding that the newer boats have this problem fixed, but I wonder if this is happening to your boat.
If I were to do what I think you explained, starting the boat and just letting it idle, I would overheat as well (if there wasn't any water in the lines already).

[Daryl]

the thermostat housing has a by-pass in it to allow for water to exit out the exhaust, regardless of engine temperature (flux is correct). I think Jeff is on the right track - check, and check again, for an air leak.

I also don't think it is healthy for an engine to run below specified operating temperature. 115 to 120 is way to low in my mind.

[aaron]

Thanks guys...will check and check again
As for Flux's input, i want to clarify that over the last few yrs, when i use a garden hose and slot it into the imput part of the water filter/strainer , if the water is running and the engine isn't, back pressure pushes my garden hose out.ONly when i start the engine does the water circulate .
So, does everyone agree that water can run thru an engine even if the engine is off?I wd have thought that the impeller (that's not spinning) will be an obstruction to water flow.

I will check if my t-stat is working properly( over a stove) and reinstall it and wait for the water to circulate.Perhaps my high temp reading was a result of "vapor-lock" which wd not allow proper intake of water.A quick stab on the throttle usually primes the system , i wd have thought.

[coloradonautique]

Aaron,
I think the bypass Flux was referring to is at the T-stat which is after the impeller. If the engine is not running, my guess is the impeller will cause enough restriction vs. the garden hose to pop it off. However if the engine is running (impeller spinning) but not at temp yet (T-stat still closed) the bypass should allow water around the T-stat and into the risers.
Ofcourse, my memory seems to recall my 91 Ski never spit water out the exhaust until after the engine got to temp. I wonder if it did not have a bypass on that older engine. I would have to look at the engine diagrams to be sure.
You definitely want to run with the T-stat. Your engine will not run efficient and clean without being at the proper temp.

-Lorin

[aaron]

Thanks guys fo yor input.Like i said maybe the " no cooling water/ overheat" situation was compounded by some"air lock" in the cooling system