How hot should the cooling water temp be? - SailNet Community
 5Likes
Reply
 
LinkBack Thread Tools
post #1 of 40 Old 12-13-2011 Thread Starter
Closet Powerboater
 
MedSailor's Avatar
 
Join Date: Mar 2008
Location: Anacortes PNW
Posts: 3,579
Thanks: 258
Thanked 112 Times in 101 Posts
Rep Power: 8
 
How hot should the cooling water temp be?

I was sailing on a friend's boat recently and noticed that cruising along with his Yanmar at 2200rpm his temp guage read about 180 deg. Mine, on the other hand never reads above 150. Usually I run my perkins 4.108 at about 24-2500rpm and my temp guage sits right around 140-145.

Does it even matter? Is coolant temp a good indicator of reaching high enough combustion temperatures? I did take 3 inches of pitch out of my prop 2 years ago due to OVER-heating issues at higher RPM. Now I'm wondering if my temp guage is telling me that I'm under-propped.

So what is the correct temp for coolant and does it even matter?

Medsailor

I have a sauna on my boat, therefore I win.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
MedSailor is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 40 Old 12-13-2011
Senior Member
 
Join Date: Dec 2003
Posts: 1,480
Thanks: 1
Thanked 26 Times in 25 Posts
Rep Power: 12
 
My Perkins used to run at an indicated temp of 140 at 2200 rpm's but less at lower rpms. My Yanmar runs at 160 once it warms and stays there. I believe it depends on the thermostat, the Perkins was overcooled to the point it couldn't maintain temp at low speed I think.

"Just call me TB"
capttb is offline  
Quote Quick Reply Share with Facebook
post #3 of 40 Old 12-13-2011
Senior Member
 
RichH's Avatar
 
Join Date: Jul 2000
Location: Pennsylvania
Posts: 3,563
Thanks: 25
Thanked 167 Times in 156 Posts
Rep Power: 16
 
A FWC engine should be running near 180F at near max. rpm. A raw water cooled engine should be running 'under' 150 to lessen the fouling of the cooling water circuit.

180 gives an optimum development of Horsepower.

Of course all this depends on the integrity of the thermostat and the temperature of the inlet raw cooling water. An engine that is below the optimum operating temp. will have a slightly less combustion efficiency ... and an ever so slightly greater wear profile of the mechanical parts due to 'metal to metal clearances' at the lower temperature.
RichH is offline  
Quote Quick Reply Share with Facebook
post #4 of 40 Old 12-13-2011 Thread Starter
Closet Powerboater
 
MedSailor's Avatar
 
Join Date: Mar 2008
Location: Anacortes PNW
Posts: 3,579
Thanks: 258
Thanked 112 Times in 101 Posts
Rep Power: 8
 
Quote:
Originally Posted by RichH View Post
A FWC engine should be running near 180F at near max. rpm. A raw water cooled engine should be running 'under' 150 to lessen the fouling of the cooling water circuit.

180 gives an optimum development of Horsepower.

Of course all this depends on the integrity of the thermostat and the temperature of the inlet raw cooling water. An engine that is below the optimum operating temp. will have a slightly less combustion efficiency ... and an ever so slightly greater wear profile of the mechanical parts due to 'metal to metal clearances' at the lower temperature.
Hmmm.... me thinks I should get an infared thermometer to check the accuracy of my gauge. Then, if the engine temp is still too low I could use that to assume that I'm under-propped could I?

BTW my engine is FWC and max rpm is, unfortunately, a debatable issue on the 4.108. From what I can tell max is 3000rpm. Any idea what temp it should be at cruising RPM? By cruising rpm I mean where the max HP/Torque/efficiency curves meet which is about 2300rpm for me.

Medsailor.

I have a sauna on my boat, therefore I win.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
MedSailor is offline  
Quote Quick Reply Share with Facebook
post #5 of 40 Old 12-14-2011
Senior Member
 
Join Date: Feb 2011
Location: San Francisco Bay area
Posts: 2,679
Thanks: 5
Thanked 63 Times in 63 Posts
Rep Power: 5
 
Quote:
Originally Posted by MedSailor View Post
Hmmm.... me thinks I should get an infared thermometer to check the accuracy of my gauge. Then, if the engine temp is still too low I could use that to assume that I'm under-propped could I?

BTW my engine is FWC and max rpm is, unfortunately, a debatable issue on the 4.108. From what I can tell max is 3000rpm. Any idea what temp it should be at cruising RPM? By cruising rpm I mean where the max HP/Torque/efficiency curves meet which is about 2300rpm for me.

Medsailor.
I'm more familiar with car engines but my understanding is that it's the thermostat that determines operating temperature, not load - unless the thermostat is fully open which would indicate a cooling system with insufficient capacity.

If you think the engine is running too cool the solution lies with changing the thermostat, not adjusting the prop.
BarryL and SloopJonB like this.

Bristol 31.1, San Francisco Bay
MarkSF is offline  
Quote Quick Reply Share with Facebook
post #6 of 40 Old 12-14-2011
Senior Member
 
RichH's Avatar
 
Join Date: Jul 2000
Location: Pennsylvania
Posts: 3,563
Thanks: 25
Thanked 167 Times in 156 Posts
Rep Power: 16
 
Agree with Mark .... probably a faulty thermostat. You can descale or replace.

With an IR thermometer you should 'profile' the temperatures. Inlet raw temp., all the inlets/outlets of the Hx, the outlet temp. of the exhaust manifold, the exit temp. (and quantity of water) at the overboard throughhull. Its the 'terminal differences' between the Hx in/out connections that are most important when checking. BTW - all such readings should be taken with the engine under 'full load', max. cruising throttle and after the engine has 'fully' warmed up (heat soaked).
RichH is offline  
Quote Quick Reply Share with Facebook
post #7 of 40 Old 12-14-2011
Senior Member
 
Join Date: Feb 2011
Location: San Francisco Bay area
Posts: 2,679
Thanks: 5
Thanked 63 Times in 63 Posts
Rep Power: 5
 
Quote:
Originally Posted by RichH View Post
Agree with Mark .... probably a faulty thermostat. You can descale or replace.

With an IR thermometer you should 'profile' the temperatures. Inlet raw temp., all the inlets/outlets of the Hx, the outlet temp. of the exhaust manifold, the exit temp. (and quantity of water) at the overboard throughhull. Its the 'terminal differences' between the Hx in/out connections that are most important when checking. BTW - all such readings should be taken with the engine under 'full load', max. cruising throttle and after the engine has 'fully' warmed up (heat soaked).
In my case, max. cruising throttle is the setting where the engine is on the verge of being too hot.

Bristol 31.1, San Francisco Bay
MarkSF is offline  
Quote Quick Reply Share with Facebook
post #8 of 40 Old 12-14-2011
Senior Moment Member
 
SloopJonB's Avatar
 
Join Date: Jun 2011
Location: West Vancouver B.C.
Posts: 11,615
Thanks: 60
Thanked 72 Times in 69 Posts
Rep Power: 5
 
Some of the comments on this thread linking props to engine operating temp. are a bit off IMHO. Engine operating temp should be regulated SOLELY by the thermostat - that's what it's there for.

A marine engine should be able to reach maximum recommended (operating) RPM, or near it, at hull speed. More specifically, it should reach its peak TORQUE rpm. Prop dimensions control THIS and should not control engine temp.

If you have a functioning thermostat of the correct temp (per the engine manufacturer) and are having cooling or heating problems, the solution is elsewhere. If you overheat you either have circulation problems of one sort or another, you have an inadequate heat exchanger (unlikely if it is OEM) or you are over-propped, in which case your max RPM should be too low.

Over cooling usually just means a thermostat problem (too low a setting or stuck open) or running the engine too slow (not an inability to run it faster).

Many people seem to think an engine is better off running cooler - 150 or even less - but this is not true. Take a look at contemporary cars - they run close to 220 before the fans even come on, racers run way over 200 as well - it gives you more power. Those temps don't leave much margin for problems though.

Engine oil needs to be hot to work properly so I like to see an engine run 180 - 190 in my boats.
boatpoker and Capt Len like this.

I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
SloopJonB is offline  
Quote Quick Reply Share with Facebook
post #9 of 40 Old 12-14-2011
Senior Member
 
Join Date: Feb 2011
Location: San Francisco Bay area
Posts: 2,679
Thanks: 5
Thanked 63 Times in 63 Posts
Rep Power: 5
 
Another issue is condensation in the engine oil. Higher oil temperature means the water etc. gets driven off more effectively and more quickly.

Bristol 31.1, San Francisco Bay
MarkSF is offline  
Quote Quick Reply Share with Facebook
post #10 of 40 Old 12-14-2011
Dirt Free
 
boatpoker's Avatar
 
Join Date: Jul 2008
Location: Toronto
Posts: 1,170
Thanks: 9
Thanked 33 Times in 32 Posts
Rep Power: 8
 
Quote:
Originally Posted by SloopJonB View Post
Some of the comments on this thread linking props to engine operating temp. are a bit off IMHO. Engine operating temp should be regulated SOLELY by the thermostat - that's what it's there for.

A marine engine should be able to reach maximum recommended (operating) RPM, or near it, at hull speed. More specifically, it should reach its peak TORQUE rpm. Prop dimensions control THIS and should not control engine temp.

If you have a functioning thermostat of the correct temp (per the engine manufacturer) and are having cooling or heating problems, the solution is elsewhere. If you overheat you either have circulation problems of one sort or another, you have an inadequate heat exchanger (unlikely if it is OEM) or you are over-propped, in which case your max RPM should be too low.

Over cooling usually just means a thermostat problem (too low a setting or stuck open) or running the engine too slow (not an inability to run it faster).

Many people seem to think an engine is better off running cooler - 150 or even less - but this is not true. Take a look at contemporary cars - they run close to 220 before the fans even come on, racers run way over 200 as well - it gives you more power. Those temps don't leave much margin for problems though.

Engine oil needs to be hot to work properly so I like to see an engine run 180 - 190 in my boats.
Clearly explained and concise. A worthwhile post, thank you.
SloopJonB likes this.

Dirt People Scare me
boatpoker is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Cooling water over temp light and buzzer DoraPearl09 Electrical Systems 5 10-21-2009 08:33 PM
Fresh Water cooling water dirty brown sailak Gear & Maintenance 17 07-31-2009 11:52 PM
Connecting raw water cooling to water heater Northeaster Gear & Maintenance 18 04-28-2007 06:11 PM
Refrigeration -Using the water tank as a cooling water source HenryRusty Gear & Maintenance 7 03-29-2007 12:14 AM
convert from sea water to fresh water cooling.... john232 Gear & Maintenance 3 02-16-2004 03:44 PM

Posting Rules  
You may post new threads
You may 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome