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Old 06-28-2014, 09:54 PM
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80starsmn 80starsmn is offline
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How hot is too hot?

I hope this is not another LT-1 temp saga thread. I would just like to know what is too high of a temp to see on a LT-1. I have a 96 Prostar190 LT-1, Hurth 1:1, new 160 (drilled) top and 143 lower T stats, steam tube service bulletin complied with, new impeller, no obstructions in cooler strainer or any other hoses, and no water leaking from water pump weep hole. My temp holds at a very steady 160 during operations, but... with a brief shut down to pick up a skier followed by a restart I will get a heat soak temp at startup from 180-200. Under way again the temp will continue to climb around 210 and then take a sharp rapid dive back to 160.

Does this behavior seem normal?
Is it an indication the engine water circulation (not raw water) pump is inefficient?
How hot before there is a head warp issue? Looks like threads on this engine when in a car is allowed to run in the 225+ range.

Thanks
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Old 06-28-2014, 10:09 PM
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cars are allowed to run that hot because of the pressure in the radiator won't allow the water to boil, it's better for emissions and it will make more power.

As far as the some in temp could be a slow t-stat or even air trapped somewhere
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Old 06-28-2014, 10:32 PM
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Make sure the thermostats are installed in the correct direction (with the pellet in the hot water). If you know they are, you might drill a second hole in the 160 and see how it works out. I agree with 1redTA about it sounding like air pockets.
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Old 06-28-2014, 10:39 PM
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Quote:
Originally Posted by Table Rocker View Post
Make sure the thermostats are installed in the correct direction (with the pellet in the hot water). If you know they are, you might drill a second hole in the 160 and see how it works out. I agree with 1redTA about it sounding like air pockets.
Yup, t stats are in the proper direction and I believe that 160 came with two possibly 3 holes drilled. Shouldn't the system self bleed? Steam tubes run off front of heads and are not plugged. Are others bleeding their systems every season after draining or t stat replacement?
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Old 06-29-2014, 08:53 AM
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On the cooling fix...most of the barbed male fittings are 1/4 inch except the last one that leads to the starport exhaust riser...that one should be 3/8th to allow a least path of resistance. You could double check that.

Also...I have read that slowly raising temps can be caused by starting to fail manifolds/ risers.

All just food for thought.

Oil level, oil type maybe.
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Old 06-29-2014, 10:36 AM
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Thanks for the ideas but oil type (Mobil 1 20/50) isn't the issue and the steam tube modification was the parts kit direct from MC, so I don't believe that is a player.

This morning temp peaked from cold start up to around 190-200 during taxi out then dropped to 160 as soon as I hit 20mph. It never moved from 160 no matter how hard I ran including 3+ mins at wot. Pulled it back to idle, sat idling for 5mins, temp never moved off 160, taxied back to dock and let sit idling another 10mins, temp never moved off 160. When I go back out to run I bet I'll get another initial 190-200 temp peak followed by a steady 160 after under way. I actually think this is perfectly normal, I am guessing there isn't any problem. I am mostly interested if anybody knows if this is typical and at what peak temp may cause damage to the aluminum heads?
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Old 06-29-2014, 11:53 AM
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Just curious...how long from cold start does it take to reach 160 and above? Just for reference....I need to idle for 10 minutes before I hit 160 and more often than not take off before.
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Old 06-29-2014, 08:00 PM
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I'll time it tomorrow morning from cold soak to 160, I would guess around 10 mins is correct.
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Old 06-29-2014, 08:06 PM
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Btw, we put 4 hrs of skiing, boarding and skating on today. I didn't shut it down between skiers and the temp never moved more that +5ish the whole time. I did get a brief peak of 180 after shutting down for lunch and dinner, but returned to normal 160 after first pull. I'm thinking normal...
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Old 07-01-2014, 11:24 AM
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Quote:
Originally Posted by mgs96ps View Post
Just curious...how long from cold start does it take to reach 160 and above? Just for reference....I need to idle for 10 minutes before I hit 160 and more often than not take off before.
I didn't time my warm up from cold soak but 10 mins at idle was about correct. I believe trapped air after my thermostat replacement was the culprit to initial high to rapidly normal fluctuations in temp. The boat has been in the water for 4 days and I am not seeing that large temp swing anymore. Thank you all for your help.
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