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Conference vicki::boats

Title:	Powerboats
Notice:	Introductions 2 /Classifieds 3 / '97 Ski Season 1267
Moderator:	KWLITY::SUTER

Created:	Thu May 12 1988
Last Modified:	Wed Jun 04 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	1275
Total number of notes:	18109

193.0. "Thermostat for Mercruiser 260 I/O" by NERSW5::BOREN () Tue Oct 25 1988 15:03

I have a 1988 Wellcraft 250 Sportsman with a Mercrusier 260 I/O.
It has approx 40 hours on it. Last Sunday after not using the boat
for 5 to 6 weeks ( I have started it weekly) I was heading out at
6:00 AM to do some fishing. I started the engine and went about 
making things ready while it was warming up. When I checked the 
temp gauge I noticed that it had gone up higher than normal and
was still climbing, I shut down and checked the 'leg' and brushed
around the intake holes. I restarted engine and the temp went back
to above normal.

Well a friend suggested changing the thermostat. I was able to get
the parts this Sat and changed thermo Sun.

Thru the summer the temp gauge has consistently read 160-165 degrees.
After installing the new thermo the gauge reads approx 145.

The manual calls for a 143 degree thermo and this is what I installed
I have to believe that the one I removed was the same.

Question:

Is it likly that the original thermo was defective and therfore ran at
the 160-165 range?

Does anyone have the same engine and recall what it normally idles at?

Someone told me that because the sea water is cooler now that the 
engine would run cooler...I don't know if I go for that answer.
It is sea water cooled vs. freshwater heat exchanger.
Thanks 4 any advice
Ernie

T.R	Title	User	Personal Name	Date	Lines
193.1	sounds ok to me	SEDJAR::JOYCE		`Wed Oct 26 1988 07:09`	6
	I would tend to agree that your seeing the difference in water temp between the summer to fall. On some boats during the summer they can see a change in engine temp when running between inshore and offshore waters. Steve
193.2	Tropical Water's	AD::GIBSON	Lobst'a Ayah	`Wed Oct 26 1988 09:57`	11
	I have to go along with Steve. You say it's raw water cooled; So naturally you get larget fluctations than if it was a closed loop system with heat exchanges. Caution- Keep an eye on the temp gage and carry a spare raw water pump impeller onboard, With the tools to change it. You might have had something clogging the intake and it only takes a couple of minutes to blow the impeller or at least damage it. Walt
193.3	160 is too high	BAGELS::MONDOU		`Thu Oct 27 1988 13:54`	14
	I have to disagree. I also own a Wellcraft Sportsman with the same engine. Normal operating temperature for this unit with raw water cooling is about 145 degrees. The factory specifies two thermostats; one for a closed cooling system and the second for raw water cooling. I don't recall the exact temperature ranges but a lower range thermostat is used for raw cooling. I believe the lower range is specified for salt water use and helps prevent salt from seperating out of the cooling water and building up in the engine. I also run my boat in Narragansett as does the originator of this note and I do not see a 20 degree rise over the summer. BTW: You can't change the water pump impeller on this unit without removing the I/O unit from the boat and disassembling it. Not exactly designed for maintainability. .
193.4	Thanks for replies	NERSW5::BOREN		`Thu Nov 03 1988 13:23`	11
	Thanks for the replies. Seems that reply .3 is correct. I spoke with the service mgr. at the dealer's and he said it should run at the 145 range. Said that they had quite a few problems with thermostats and it is quite possible that it has been bad since day one (of course that makes me wonder why it wasn't caught at dealer prep/checkout time). He also said that the engine would probably run better at the 165 temp, but they run it cooler for salt water because of seperation or crystalyzing of the salt. Thanks again for replies Ernie