Do you need a T Stat

[mala1967]

Have a 98 Nautique w/351 5.8 . It started to run hot this weekend thought it was a TStat so I took it out and also check to see if the strainer was clogged and it still overheated at idle and while cruising. Going to replace the water pump now anything else I should check and do you need a T Stat at all.

[ClemsonDave]

Yes, you need a thermostat. Motors are not efficient if they get too cool. Stock should be in the 160* range. Modern thermostats are designed to fail in the open position. It will not harm the motor, but it will not be efficient.

9 times out of 10, overheating is caused by the impeller falling apart. The 1 out of 10 is debris clogging the system somewhere.

[mala1967]

Thanks I will put one in. Do you think it is the water pump.

[ClemsonDave]

Check the rubber impeller in the water pump. White Lake Marina (site sponsor) is a good place to get a replacement and they offer a discount to members of this site.

[slob02]

Check water strainer if you recently cleaned it. Make sure the rubber o-ring is there.

[mala1967]

Thanks for the help I appreciate it and will post once I get the boat fixed

[horkn]

Actually the stock T stat temp is 143 degrees for open cooling systems, and yes, you need one.

Some guys have used 160 degree t stats, but it will run much hotter than it is supposed to. Even with a 143 degree t stat, it will get to 160 usually.

if you are in a pinch and can't get 143 t stat and you need to get on the water,a 160 will work, but I would replace it with a 143 after the weekend.

As far as another reasons a boat over heats, another culprit is seaweed and gunk blocking the sea strainer/ tranny cooler. That's an easy fix though.

[ClemsonDave]

All of mine (listed in my signature) have had a 160* from the factory. I have 2 friends with '97s that have 160s. Page 1.2 in the manual for the '98 says 160* is the normal operating temp. http://www.planetnautique.com/Correc.../1998/1998.pdf

Per White Lake's website:
"Thermostat - PCM Ford carbureted Engines ( most PCM engines prior to 1995) - 143 degrees, comes with gasket."
"Thermostat - PCM Ford Engines - 160 degree, comes with gasket. For newer (1994-up) EFI systems."

[horkn]

Ahhh, thanks for the correction. Makes you winder why they didn't put a 143 in them when they were carbed.

[jpduster]

I was told once that running without a thermastat in place can cause overheating. The coolant passes through the radiator*(*car) too fast to be cooled effectively.

[mala1967]

Well ClemsonDave thanks for the advise. I just took off the water pump and the impeller fins were destroyed. I changed it and the T Stat. I guess I am lucky it is the first time I have changed it and its a 1998. Thanks again for all of the advise

[NautiqueJeff]

Make sure you find the remnants of those fins. They're in the cooling system somewhere.

[ClemsonDave]

Make sure you find the remnants of those fins. They're in the cooling system somewhere.

I agree with Jeff. Look for a small canister that is sitting horizontal on the passenger side. Remove the hoses and see if any got caught there. It has a screen of sorts on each side. That's a popular place for stuff to hide.

When you get the new impeller, buy 2 and keep the spare in the boat just in case.

[AirTool]

Make sure you find the remnants of those fins. They're in the cooling system somewhere.

Read with the theme music from the movie "Jaws" playing in the background.

[horkn]

Make sure you find the remnants of those fins. They're in the cooling system somewhere.

On the older boats like mine, most fins simply go into the lake. Some got stuck in the t stat housing, and some stayed in the exhaust manifold logs until I drained them.


Glad to hear it was simply an impeller issue.