Reply
 
Thread Tools Display Modes
 
Old 07-13-2013, 06:11 PM   #1
Guru
 
City: somewhere
Country: USA
Join Date: Jan 2013
Posts: 1,356
Proper Engine Operating Temperature?

I have 7.4 Mercruisers gas engines in my boat. One engine runs in the high 140's and the other one in the mid 150's.

I think they should be running around 165-170 degrees.

What is the factory recommendation?

Dave
__________________
Advertisement

__________________
Life is a Beach
beachbum29 is offline   Reply With Quote
Old 07-13-2013, 06:36 PM   #2
Guru
 
rochepoint's Avatar
 
City: Sidney BC
Country: Canada
Vessel Name: Rochepoint
Vessel Model: 1985 Cheer Men PT38 Sedan
Join Date: Apr 2009
Posts: 1,191
Have a look here.
__________________

__________________
Cheers Mike Barge
MV Rochepoint
Sidney, British Columbia.
"Yes, I have the right anchor"
rochepoint is offline   Reply With Quote
Old 07-13-2013, 06:48 PM   #3
Guru
 
City: Hotel, CA
Country: Fried
Join Date: Sep 2011
Posts: 8,328
Quote:
Originally Posted by rochepoint View Post
Have a look here.
Great resource, thanks!
__________________
Craig

It's easier to fool people than to convince them that they've been fooled - Mark Twain
CPseudonym is offline   Reply With Quote
Old 07-13-2013, 07:17 PM   #4
Guru
 
City: somewhere
Country: USA
Join Date: Jan 2013
Posts: 1,356
Great link, thanks. They say 160 so they are running a little cold.
__________________
Life is a Beach
beachbum29 is offline   Reply With Quote
Old 07-13-2013, 07:35 PM   #5
Guru
 
rochepoint's Avatar
 
City: Sidney BC
Country: Canada
Vessel Name: Rochepoint
Vessel Model: 1985 Cheer Men PT38 Sedan
Join Date: Apr 2009
Posts: 1,191
Want are the exact model numbers, bet there is a complete manual available online?
__________________
Cheers Mike Barge
MV Rochepoint
Sidney, British Columbia.
"Yes, I have the right anchor"
rochepoint is offline   Reply With Quote
Old 07-13-2013, 07:46 PM   #6
Guru
 
City: somewhere
Country: USA
Join Date: Jan 2013
Posts: 1,356
Quote:
Originally Posted by rochepoint View Post
Want are the exact model numbers, bet there is a complete manual available online?
How could I find that out?
__________________
Life is a Beach
beachbum29 is offline   Reply With Quote
Old 07-13-2013, 08:22 PM   #7
Guru
 
rochepoint's Avatar
 
City: Sidney BC
Country: Canada
Vessel Name: Rochepoint
Vessel Model: 1985 Cheer Men PT38 Sedan
Join Date: Apr 2009
Posts: 1,191
This site has the manual covering your engines, quite a large PDF.
__________________
Cheers Mike Barge
MV Rochepoint
Sidney, British Columbia.
"Yes, I have the right anchor"
rochepoint is offline   Reply With Quote
Old 07-13-2013, 08:28 PM   #8
Guru
 
City: somewhere
Country: USA
Join Date: Jan 2013
Posts: 1,356
Quote:
Originally Posted by rochepoint View Post
This site has the manual covering your engines, quite a large PDF.
Thank you.

When I get on my desktop, I'll download it.
__________________
Life is a Beach
beachbum29 is offline   Reply With Quote
Old 07-13-2013, 10:32 PM   #9
Guru
 
boatpoker's Avatar
 
City: Port Credit
Country: Ontario
Vessel Name: DIRT FREE
Vessel Model: Benford Fantail 38
Join Date: Sep 2012
Posts: 2,011
Before you get too upset about temperature differences be aware that dashboard gauges are not entirely reliable. Borrow or buy an infrared thermometer and check the engines directly.
boatpoker is offline   Reply With Quote
Old 07-14-2013, 06:19 AM   #10
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,518
The real question is how is the engine cooled?

If it has a heat exchanger and operates on fresh water about 180F is the norm.

If its sea water direct cooling the temp will be closer to 140 F so the salt is not kicked out to plug the engine.
FF is offline   Reply With Quote
Old 07-14-2013, 07:55 AM   #11
Guru
 
City: somewhere
Country: USA
Join Date: Jan 2013
Posts: 1,356
Quote:
Originally Posted by boatpoker View Post
Before you get too upset about temperature differences be aware that dashboard gauges are not entirely reliable. Borrow or buy an infrared thermometer and check the engines directly.
I'm using the numbers from the B&G engine management system, not the dash gauges.
__________________
Life is a Beach
beachbum29 is offline   Reply With Quote
Old 07-14-2013, 07:56 AM   #12
Guru
 
City: somewhere
Country: USA
Join Date: Jan 2013
Posts: 1,356
Quote:
Originally Posted by FF View Post
The real question is how is the engine cooled?

If it has a heat exchanger and operates on fresh water about 180F is the norm.

If its sea water direct cooling the temp will be closer to 140 F so the salt is not kicked out to plug the engine.
It's raw water cooled.
__________________
Life is a Beach
beachbum29 is offline   Reply With Quote
Old 07-14-2013, 08:05 AM   #13
Guru
 
jleonard's Avatar
 
Join Date: Jun 2008
Posts: 2,738
I had a Criscraft that was raw water cooled and it called for a 140 F thermostat for the reasons FF dexcribed. When running the gage would show about 145 or so.
__________________
Jay Leonard
Attitude Adjustment
40 Albin
Mystic,Ct. /New Port Richey,Fl
jleonard is online now   Reply With Quote
Old 07-14-2013, 08:58 AM   #14
Guru
 
City: somewhere
Country: USA
Join Date: Jan 2013
Posts: 1,356
Quote:
Originally Posted by jleonard View Post
I had a Criscraft that was raw water cooled and it called for a 140 F thermostat for the reasons FF dexcribed. When running the gage would show about 145 or so.
It just seems that running at this temp creates inefficient combustion chamber temps that results in carbon build up and much lowered fuel economy.
__________________
Life is a Beach
beachbum29 is offline   Reply With Quote
Old 07-14-2013, 10:35 AM   #15
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,707
I believe FF and beachbum29 is spot on here.

Sea water cooled must run stone cold (130) or less to keep from salting.

Closed loop cooling can be run cool at 170 or even 160 but the hotter the better. I'd say run 190 if you can. Especially if you're running at a 40% load or less. That probably includes well over 50% of TF members. One should do everything one can to get the operating temp up. And if your cooling system is in good shape and w about 40/60 (AF/water) we should be able to run well over 200 as w the AF and pressure I think the boiling point is about 240 degrees. I run 190 in my Mitsu.
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 07-14-2013, 10:48 AM   #16
Guru
 
Codger2's Avatar
 
City: San Diego
Country: US
Vessel Name: "Sandpiper"
Vessel Model: 2006 42' Ocean Alexander Sedan
Join Date: Oct 2007
Posts: 5,420
Quote:
Originally Posted by manyboats View Post
I run 190 in my Mitsu.
It's been well documented that my Cummins runs at 192 no matter what. I've also been told by some "experts" that the newer engines run hotter to achieve a more complete fuel burn. I'd like to know what RickB's take is on this.
__________________
Codger2

My passion for improving my boat(s) exceeds my desire to constantly cruise them.
Codger2 is offline   Reply With Quote
Old 07-14-2013, 11:59 AM   #17
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,361
Quote:
Originally Posted by beachbum29 View Post
It just seems that running at this temp creates inefficient combustion chamber temps that results in carbon build up and much lowered fuel economy.
Many boats like yours are sold to fresh water lake dwellers where raw water cooling is ok at 160 to 180F. Years ago when I worked at a LI boatyard the annual chore on Atomic 4s was to clean out the cooling passages, never possible to get them 100% clean with cratered engines quite common.

For salt water cruising heat exchangers became a much desired item or run them at 140 as FF says where you correctly note combustion temps are possibly too low.

Why not convert to fresh water cooling? Easy enough to do with all sorts of interesting kits to choose from. It will add to the resale value of your boat too.
sunchaser is offline   Reply With Quote
Old 07-14-2013, 01:23 PM   #18
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
Quote:
Originally Posted by SeaHorse II View Post
I've also been told by some "experts" that the newer engines run hotter to achieve a more complete fuel burn.
A few years ago there were projects to develop ceramic pistons and liners so that engines could be run without cylinder lube or coolant in order to increase efficiency. I am not sure where it went but all that seems to remain are a few aftermarket ceramic coatings.

Running hotter has its limits as far as benefits go before it leads to emissions issues and complicated fixes to reduce them. It also leads to issues with thermal cycling of engines that don't operate for long periods or at constant loads for long periods.

This gets back to the angels dancing on a pinhead issue of what are you willing to pay for a one percent increase in efficiency to drive a recreational boat around for a few hours a week? Steering a straight line might provide better returns.

Back on topic ... once you heat seawater above about (about because the makeup of seawater varies considerably with location) 150F or 65C you will start to plate the liners with insoluable calcium carbonate. That forms an insulating layer that just makes things worse and requires acid washing to remove it along with a bit of your cooling passages.

Keeping a raw seawater cooled engine in the 140 - 145F range will provide good service and better if lower but then you run into lube oil issues due to moisture.
RickB is offline   Reply With Quote
Old 07-14-2013, 02:01 PM   #19
Guru
 
City: somewhere
Country: USA
Join Date: Jan 2013
Posts: 1,356
Very interesting posts. Thank you. Guess I'll leave well enough alone.
__________________
Life is a Beach
beachbum29 is offline   Reply With Quote
Old 07-14-2013, 02:29 PM   #20
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,707
I agree w Tom. FWC.
__________________

__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Reply

Thread Tools
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





All times are GMT -5. The time now is 08:20 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012