View Full Version : 2 thermostats??

jazz n ski
05-02-2010, 10:23 PM
I have a 1994 Maristar with the LT-1. I have seen some threads saying there are two thermostats on that motor. One is pretty simple to find that comes off one of the hoses of the impeller where's the other tstat? My engine seems to overheat quickly when in idle or very low RPM's. I am Trying to go through all the cooling system to resolve issue. Usually when it starts overheating i can give it gas and the engine cools down quickly, but this time I tried to give it gas and it the engine just bogged down, also saw smoke/steam out of the muffler, so I shut it down after a few minutes and not being able to rev the engine up because it was bogging down and the temp getting up close to 200. Any ideas on what might be up? I am currently going through the impellar, hoses, and other tstat.

05-02-2010, 10:29 PM
sounds like blockage in the lines pulling water in to the boat ..... check your raw water scoop at the bottom of the boat ..... tranny cooler inlets ..... and the impeller .... bet you clear up some blockage and then a new impeller and life will be better.

jazz n ski
05-02-2010, 10:31 PM
Thanks for the tips. I will hope it is as simple as doing those. Thanks

05-03-2010, 12:02 PM
Also, as an owner of an early LT-1 you shouldm take a look at this thread:



jazz n ski
05-03-2010, 09:59 PM
Thanks for your help. Never did find this 2nd thermostat people talk about. I went through the entire cooling system checking for blockage and trash and found nothing. I put it back together with a new thermostat and new impellar and it runs like a champ now. Hopefully that overheating problem people talk about won't start bothering me, after all it hasn't yet for 12 years.

05-03-2010, 10:00 PM
I bet you will be just fine! good work.

05-04-2010, 09:53 AM
I have a 96 with the TBI so it might be different but I just discovered mine last weekend. The normal one is in the normal location in the intake manifold like in a car. The other one is in the triangle shaped block on top of the engine. It routes the water out to the exhaust manifolds. Take off the three bolts and there it is. It keeps the water from going out to the exhaust manifolds when closed. I removed mine because it was stuck. Can anyone tell me why this one is necessary?

05-04-2010, 10:34 AM
That ebgine is supposed to have two thermostats.

The lower thermostat 143 degrees (found on the front of the engine abve the raw water pump) tempers the water entering the cooling system to avoid thermal shock.

The upper t-stat is a special two way thermostat that requires a drilled hole, it runs at 163 degrees. This thermostat controls both the entry and exit of cooling water, as well as bypass of the block when cooling is not called for. This must be the correct thermostat; and this controls the operating temperature of the engine.

On engines where there is an overheat problem, it is not uncommon to find that previous owners have removed this upper t-stat. This is NOT the desired solution as the engine will run too cold.

Go over every single hose and opening looking for blockages. Test the raw water pump to see that enough water is getting through.

It will be worth the effort to get this engine running correctly.

Good luck:)