Low Engine Temp question

Chaos · 04-21-2010, 12:14 AM

I just took delivery of a new boat (new for me) last week. On my maiden voyage I noticed the engine temps (twin mercs) were reading low. They were at about 85 degrees after 30 minutes of idling and then after a relatively energetic pace from Weirs to West Alton Marina, they only got to about 100.

I would have expected about 160 after running for a bit, even with the 45 degree water, and of course a bit higher after the cruise.

I ran through all the smartcraft calibrations and settings and no change. The dealer believes that maybe both thermostats were removed.

Has anyone out there had a similar experience?

Twin Mercury 4.3MPI 220HP with Alpha drives.

VitaBene · 04-21-2010, 04:10 AM

That is a low temp to be running and it may very well be because your Tstats were removed. Frankly if it were a car I would say there needs to be thermostats to heat the water to make heat in the car but in a boat that is not the case.

My boat runs cool- 130 max is my recollection and we have approx 300 hours on this engine.

What did the dealer say, is there any harm that can come from being too cool?

Dave R · 04-21-2010, 04:47 AM

You'll get excessive wear from running too cold. Put the proper thermostats in if they are missing.

Blue Thunder · 04-21-2010, 05:23 AM

The engines need to be at operating temperature to perform properly. If your thermostats are missing and I agree with the others, I think they are, you should have new ones installed. Your operating temp will increase as the lake temp increases but I wouldn't wait until July to get a comfort level. Cheap enough fix, given you are running twins.

BT

BroadHopper · 04-21-2010, 09:22 AM

Newer engines are built with close tolerances and the engine control modules are temperature sensitive. i would put in the proper thermostats. The older engines without ECM can survive without tstat but engine wear will increase. Tstat are cheap but good investments.

If you drain the block for winterizing, you may want to drill a 1/4 or 3/8 inch hole on the flat plate that holds the spring mechanism. That will allow the water to drain.

LIforrelaxin · 04-21-2010, 09:31 AM

As everyone else here has recommend I would get the new thermostats and put them in. It shouldn't be a big job at all. Engines are always set up to run at operating temperature. Not only is where etc a concern. But timing setting, etc are all based on the engine coming up to temperature. These things are compensated for when the engine is cold.

My guess would be if they thermostats are currently not there, that some shade tree mechanic or early owner removed them when they were stuck shut or only partially opening in the summer. Not a big deal if you only use the boat in late June thru early Aug. but when the weather is cooler you want to be able to heat that puppy up.

Chaos · 04-21-2010, 04:17 PM

Thanks everyone.

That is what the dealer thought. Since they are doin' the fixin' I don't know that I care what the problem is, other than to know for the future. When I get a resolution, I'll be sure to update the post.

Thanks again,
Mike

NoBozo · 04-21-2010, 06:29 PM

Raw water cooled engines used in fresh water can be run as high as 180. Raw water cooled engines run in Salt Water should be run at +/- 140. Raw water cooled engines run in BOTH Salt and Fresh can be run at 160 if they are flushed after each use in Salt.

A thermostat is manditory in either case to maintain constant engine temperature.

If raw water cooled engines are run HOT in Salt water, they will Salt Up. Not good in the long run.

I have run my Donzi in Salt water maybe 10% of the time and 90% Fresh water for the past 14 years and no sign of salting up.....always flush after salt water running. HOWEVER.. cast iron exhaust risers will still rust out ...in my case in about 10 years. Manifolds less so.

SO: How do you tell if you need NEW Risers or Manifolds: The engine will be reluctant to Start..when it does it will run ragged. You may be able to run fast, but when coming off plane to idle the engine will run Sucky.

Start pullung the spark plugs one at a time on ONE side of the engine. If you find a plug....probably more than one..with a big drop of water on the plug electrode...ie: WET plug. You probably need to replace the riser on that side. The riser goes first. Manifolds last longer.

My experience has been (350 V8 SBC) the left side always seems to go first. I can't explain why.

What is happening: Water is getting into the cylinders from the Rusted Through riser or manifold. Time to replace. There is no Shortcut. NB

MAXUM · 04-21-2010, 07:06 PM

yuck - good example of why my boat will never see salt water.

Amazing that happens even with you flushing the engine. I was always under the impression that as long as you were religious about flushing after use rusting would never be a concern. Huh learn something new every day!

04-21-2010, 12:14 AM	#1
Chaos Senior Member Join Date: Apr 2009 Location: Danville, NH and West Alton Marina Posts: 134 Thanks: 111 Thanked 32 Times in 20 Posts	Low Engine Temp question I just took delivery of a new boat (new for me) last week. On my maiden voyage I noticed the engine temps (twin mercs) were reading low. They were at about 85 degrees after 30 minutes of idling and then after a relatively energetic pace from Weirs to West Alton Marina, they only got to about 100. I would have expected about 160 after running for a bit, even with the 45 degree water, and of course a bit higher after the cruise. I ran through all the smartcraft calibrations and settings and no change. The dealer believes that maybe both thermostats were removed. Has anyone out there had a similar experience? Twin Mercury 4.3MPI 220HP with Alpha drives.

04-21-2010, 05:23 AM	#4
Blue Thunder Senior Member Join Date: Apr 2004 Location: Eastern MA & Frye Island/Sebago Lake, Maine Posts: 935 Thanks: 247 Thanked 323 Times in 148 Posts	The engines need to be at operating temperature to perform properly. If your thermostats are missing and I agree with the others, I think they are, you should have new ones installed. Your operating temp will increase as the lake temp increases but I wouldn't wait until July to get a comfort level. Cheap enough fix, given you are running twins. BT __________________ " Live for today because yesterday is gone and tomorrow may never come"

04-21-2010, 09:22 AM	#5
BroadHopper Senior Member Join Date: Oct 2004 Location: Laconia NH Posts: 5,512 Thanks: 3,118 Thanked 1,090 Times in 784 Posts	Thermostats Newer engines are built with close tolerances and the engine control modules are temperature sensitive. i would put in the proper thermostats. The older engines without ECM can survive without tstat but engine wear will increase. Tstat are cheap but good investments. If you drain the block for winterizing, you may want to drill a 1/4 or 3/8 inch hole on the flat plate that holds the spring mechanism. That will allow the water to drain. __________________ Someday may never be an actual day.

04-21-2010, 09:31 AM	#6
LIforrelaxin Senior Member Join Date: May 2006 Location: Long Island, not that one, the one on Winnipesaukee Posts: 2,825 Thanks: 1,016 Thanked 880 Times in 514 Posts	As everyone else here has recommend I would get the new thermostats and put them in. It shouldn't be a big job at all. Engines are always set up to run at operating temperature. Not only is where etc a concern. But timing setting, etc are all based on the engine coming up to temperature. These things are compensated for when the engine is cold. My guess would be if they thermostats are currently not there, that some shade tree mechanic or early owner removed them when they were stuck shut or only partially opening in the summer. Not a big deal if you only use the boat in late June thru early Aug. but when the weather is cooler you want to be able to heat that puppy up. __________________ Life is about how much time you can spend relaxing... I do it on an island that isn't really an island.....

04-21-2010, 04:17 PM	#7
Chaos Senior Member Join Date: Apr 2009 Location: Danville, NH and West Alton Marina Posts: 134 Thanks: 111 Thanked 32 Times in 20 Posts	Thermostats it is Thanks everyone. That is what the dealer thought. Since they are doin' the fixin' I don't know that I care what the problem is, other than to know for the future. When I get a resolution, I'll be sure to update the post. Thanks again, Mike

04-21-2010, 04:10 AM	#2
VitaBene Senior Member Join Date: Jul 2007 Location: Moultonborough Posts: 3,531 Thanks: 1,570 Thanked 1,607 Times in 822 Posts	That is a low temp to be running and it may very well be because your Tstats were removed. Frankly if it were a car I would say there needs to be thermostats to heat the water to make heat in the car but in a boat that is not the case. My boat runs cool- 130 max is my recollection and we have approx 300 hours on this engine. What did the dealer say, is there any harm that can come from being too cool?

04-21-2010, 04:47 AM	#3
Dave R Senior Member Join Date: Jul 2004 Posts: 2,974 Thanks: 246 Thanked 736 Times in 438 Posts	You'll get excessive wear from running too cold. Put the proper thermostats in if they are missing.

04-21-2010, 06:29 PM	#8
NoBozo Senior Member Join Date: Jun 2008 Location: Portsmouth. RI Posts: 2,231 Thanks: 400 Thanked 460 Times in 308 Posts	Raw water cooled engines used in fresh water can be run as high as 180. Raw water cooled engines run in Salt Water should be run at +/- 140. Raw water cooled engines run in BOTH Salt and Fresh can be run at 160 if they are flushed after each use in Salt. A thermostat is manditory in either case to maintain constant engine temperature. If raw water cooled engines are run HOT in Salt water, they will Salt Up. Not good in the long run. I have run my Donzi in Salt water maybe 10% of the time and 90% Fresh water for the past 14 years and no sign of salting up.....always flush after salt water running. HOWEVER.. cast iron exhaust risers will still rust out ...in my case in about 10 years. Manifolds less so. SO: How do you tell if you need NEW Risers or Manifolds: The engine will be reluctant to Start..when it does it will run ragged. You may be able to run fast, but when coming off plane to idle the engine will run Sucky. Start pullung the spark plugs one at a time on ONE side of the engine. If you find a plug....probably more than one..with a big drop of water on the plug electrode...ie: WET plug. You probably need to replace the riser on that side. The riser goes first. Manifolds last longer. My experience has been (350 V8 SBC) the left side always seems to go first. I can't explain why. What is happening: Water is getting into the cylinders from the Rusted Through riser or manifold. Time to replace. There is no Shortcut. NB

04-21-2010, 07:06 PM	#9
MAXUM Senior Member Join Date: Apr 2004 Location: Kuna ID Posts: 2,755 Thanks: 246 Thanked 1,942 Times in 802 Posts	yuck - good example of why my boat will never see salt water. Amazing that happens even with you flushing the engine. I was always under the impression that as long as you were religious about flushing after use rusting would never be a concern. Huh learn something new every day!