Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-18-2022, 11:00 PM   #1
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default 3.0 thermostat issues

hey,
im trying to replace the thermostat cause it started to run at 175F but i am seeing different things as to temp.

im reading some say 140F for salt water and 160F for fresh water.
official parts say 160F (part# 807252T2)

looking for some advise on which to use

also is there a trick to remove the plastic housing?

and does this black stuff look normal? it feels like dirt not grease (see pic)
Attached Thumbnails
IMG_20220518_184437415.jpg  
__________________

tech62571 is offline   Reply With Quote
Old 05-19-2022, 01:03 AM   #2
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 9,408
Default

Raw water cooled in salt water 140 F to stay below the crystallization point of salt. Not sure what the black stuff is.
__________________

__________________
1997 2400 SCR
5.7 Vortec / Bravo 2

Mike
mmwjr is offline   Reply With Quote
Old 05-20-2022, 09:58 PM   #3
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

thx for the reply..
i figured out its small pieces of rust
there is some in the hose too
is that normal?
Attached Thumbnails
IMG_20220520_175634767.jpg  
tech62571 is offline   Reply With Quote
Old 05-20-2022, 10:07 PM   #4
Captain
 
donald's Avatar
 
Join Date: Jun 2016
Location: Mn.
Posts: 619
Default

I am thinking you have a large amount of rust scale in that engine and more than likely blocking exh elbows.
Don
__________________
1995 Maxum 2400 SCR 5.7 A1 G2 LUNA DE MIEL
1988 Bayliner 2455 5.0 IO (sold)
1987 Seaswerl 18ft C. Cabin 4.3 IO(lost in fire)
1998 Alumacraft 170 Trophy Mariner 100hp/Evinrude 9.9hp
donald is offline   Reply With Quote
Old 05-20-2022, 10:38 PM   #5
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

is that normal?
can i flush that out?
tech62571 is offline   Reply With Quote
Old 05-21-2022, 12:14 AM   #6
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 9,408
Default

Yup rust scale. No easy way to clean it out. I had to replace the engine on my first boat due to this as it was causing overheating all the time. I did try removing the heads and scraping the water jackets and got one additional year out of it.
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2

Mike
mmwjr is offline   Reply With Quote
Old 05-21-2022, 08:54 PM   #7
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

ok thanks for the info.. appreciate it
tech62571 is offline   Reply With Quote
Old 05-22-2022, 03:24 PM   #8
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

i cleaned and flushed everything but it still overheating.
looks like almost all the water is coming out of the prop.

any ideas why? or where to start looking?
tech62571 is offline   Reply With Quote
Old 05-22-2022, 06:35 PM   #9
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 9,408
Default

The two ports on either side of the transom assembly are for idle and at higher rpms most of the water will come out the prop, what rpm are you at? Have you performed the flow test to verify the engine is getting the correct flow of water? See the Mercruiser manual.
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2

Mike
mmwjr is offline   Reply With Quote
Old 05-22-2022, 06:54 PM   #10
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

it was at idle
i dont know how to do a flow test
tech62571 is offline   Reply With Quote
Old 05-22-2022, 09:03 PM   #11
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 9,408
Default

Idle being 650 rpm?

See the mercruiser manual for you engine under Documents
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2

Mike
mmwjr is offline   Reply With Quote
Old 05-22-2022, 10:39 PM   #12
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

yes about 650
tech62571 is offline   Reply With Quote
Old 05-24-2022, 01:19 AM   #13
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

so i pulled the elbow and it doesnt look too bad.
i ran water through the manifold and its flowing good. doesnt look obstructed at all.
the elbow could be obstructed but i cant flow test it other then running the hose into it.

i ran water through the block and it flows good out of the head.

does this have a circulating pump? i cant think of anything else.

i put a new thermostat in but hard to tell if its working
Attached Thumbnails
1.jpg   2.jpg   3.jpg   4cyl_cooling.jpg  
tech62571 is offline   Reply With Quote
Old 05-24-2022, 01:25 AM   #14
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 9,408
Default

I would consider that end of life. Itís near the point when failure will occur allowing water to get into the exhaust.
__________________
1997 2400 SCR
5.7 Vortec / Bravo 2

Mike
mmwjr is offline   Reply With Quote
Old 05-24-2022, 01:56 AM   #15
Captain
 
donald's Avatar
 
Join Date: Jun 2016
Location: Mn.
Posts: 619
Default

I agree with Mike.
Time for new elbows and manifolds.
Don
__________________
1995 Maxum 2400 SCR 5.7 A1 G2 LUNA DE MIEL
1988 Bayliner 2455 5.0 IO (sold)
1987 Seaswerl 18ft C. Cabin 4.3 IO(lost in fire)
1998 Alumacraft 170 Trophy Mariner 100hp/Evinrude 9.9hp
donald is offline   Reply With Quote
Old 05-24-2022, 07:55 PM   #16
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

thanks guys
tech62571 is offline   Reply With Quote
Old 05-28-2022, 07:05 PM   #17
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

i replaced the elbow and im still getting the same issue.
over heating but most (almost all) of the return exhaust water is coming out of the prop.

any ideas why?

i cant figure out how the water goes to the idle ports and prop or why it changes when underway
tech62571 is offline   Reply With Quote
Old 05-28-2022, 08:17 PM   #18
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

after more troubleshooting.. i found out there is no water coming from the impeller.
is it possible the shaft that spins it has an issue?
is there a way to test that?
tech62571 is offline   Reply With Quote
Old 05-28-2022, 08:39 PM   #19
Lt. Commander
 
Join Date: May 2018
Location: Florida
Posts: 142
Default

can i run the engine briefly with the lower unit off the outdrive? to see if its spinning?
tech62571 is offline   Reply With Quote
Old 05-29-2022, 01:02 AM   #20
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 9,408
Default

If you put the shifter into gear and the propeller spins the shaft that turns the impeller is turning. Missing key, bad collar in the impeller or just worn impeller.
__________________

__________________
1997 2400 SCR
5.7 Vortec / Bravo 2

Mike
mmwjr is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 12:15 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2022, vBulletin Solutions, Inc.