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Old 05-09-2021, 11:07 PM
01star 01star is offline
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Boat: 2001 MasterCraft ProStar 209, 330 HP Indmar
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Replacing thermostat 5.7 LTR

Hey guys, boat has been running a tad warm (around 165-170 as opposed to right at 160). The raw water pump and impeller are relatively new and there is no blockage in the transmission cooler. The thermostat is original, so about 20 years old and I'm figuring it's starting to go. How often have you guys had to replace a thermostat? do my symptoms seem like a thermostat?

Who has replaced a thermostat with the 5.7 LTR motor? Is it a tough job? do I need to remove the engine plenum? I plan on calling Skidim tomorrow to get the right OEM replacement. Do I need new gaskets as well? Thanks for the input
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Old 05-10-2021, 12:00 AM
ONTHECOAST ONTHECOAST is offline
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Your temperatures are definitely in the proper range. Preventive maintenance is always a good thing. Why take a chance on such an inexpensive part. The folks at SkiDIM can fix you up.
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  #3  
Old 05-10-2021, 06:54 AM
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JimN JimN is offline
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Quote:
Originally Posted by 01star View Post
Hey guys, boat has been running a tad warm (around 165-170 as opposed to right at 160). The raw water pump and impeller are relatively new and there is no blockage in the transmission cooler. The thermostat is original, so about 20 years old and I'm figuring it's starting to go. How often have you guys had to replace a thermostat? do my symptoms seem like a thermostat?

Who has replaced a thermostat with the 5.7 LTR motor? Is it a tough job? do I need to remove the engine plenum? I plan on calling Skidim tomorrow to get the right OEM replacement. Do I need new gaskets as well? Thanks for the input
There's no special part for this- it's not a 'marine-specific' item. It does need to be a 160 degree thermostat, though. If you go colder, it will waste gas and won't run efficiently; if you go warmer, it can overheat under some circumstances and may run a bit lean.

Run the engine on the trailer and feel the hoses coming from the upper t-stat housing- the supply hoses should be cool, the others should be warm, but not necessarily hot. If you have an infrared thermometer, check the engine for hot spots and make sure the exhaust manifolds aren't hot- at idle, they should be warm but make sure the water supply can keep up with the raw water pump.

If you have a V-drive, it's not gonna be fun.
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Old 05-13-2021, 04:23 PM
01star 01star is offline
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Boat: 2001 MasterCraft ProStar 209, 330 HP Indmar
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I got the replacement thermostat (160) and gasket for the housing, are there any other parts I need to complete the job? I don't want to take everything apart and need another piece. Do I need to remove engine plenum and entire housing? or just take 2 bolts out and I can access it?
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  #5  
Old 05-13-2021, 09:51 PM
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jafo9 jafo9 is offline
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just the t-stat. its been a while for me but i don't remember having to take off anything but the t-stat. i think you have to play with one of the bolts to get it out and back in but no need to take off excess parts.
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