Engine overheating

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Palmettomoon350

Engine overheating

Post by Palmettomoon350 »

Recent overheating while running the engine at around 2500 to 3000 RPMs. After sailing in very gusty winds, 30 to 40 kts, we decided to pull the sails in and motor back to the dock. Upon leaving the dock water temp was fine, less than 160 Degrees. While motoring after sailing the temp began to rise and read 180 and appeared to be increasing. I pulled back on the throttle to less than 2000 RPM's and maintained this speed all the way back to the dock.
Exhaust elbow, water pump with all parts replaced in Oct 14.
Have not changed anti freeze this year trying to figure out what is wrong. Water exhaust is normal. At engine idle, the temp is right below 160, as normal. Putting into forward, at dock, temp will slowly rise after 10 mins or so but only to 162/163. Pulling back to neutral the temp remains above 160.
Checking engine after, the anti freeze level is at the top of manifold but the burp box is down.
Engine hours 960, heat exchange cleaned at 750/800.
I am beyond my level of competence and understanding. Suggestions???

Carl Beckmann
Palmetto Moon # 223
Last edited by Palmettomoon350 on Sun Jun 05, 2016 6:33 pm, edited 1 time in total.
canopus199@gmail.com
Posts: 4
Joined: Fri Feb 27, 2015 9:57 pm

Re: Engine overheating

Post by canopus199@gmail.com »

Check the wire connections to the temperature gauge had the same issue when running temp would creep up to 180 on hull 196
Pete Bruzik
Posts: 19
Joined: Fri Nov 11, 2005 10:40 am

Re: Engine overheating

Post by Pete Bruzik »

Hi - sounds like my issue - see post "intermittent overheat at start up"
I have not done any further investigation - waiting for spring (soon!) then I will be checking the exhaust elbow - but it looks like you already did that...
Keep us posted as to resolution - I will as well
Pete Bruzik - Pekabu 3 - #107
Palmettomoon350

Re: Engine overheating

Post by Palmettomoon350 »

Palmettomoon350 wrote:Recent overheating while running the engine at around 2500 to 3000 RPMs. After sailing in very gusty winds, 30 to 40 kts, we decided to pull the sails in and motor back to the dock. Upon leaving the dock water temp was fine, less than 160 Degrees. While motoring after sailing the temp began to rise and read 180 and appeared to be increasing. I pulled back on the throttle to less than 2000 RPM's and maintained this speed all the way back to the dock.
Exhaust elbow, water pump with all parts replaced in Oct 14.
Have not changed anti freeze this year trying to figure out what is wrong. Water exhaust is normal. At engine idle, the temp is right below 160, as normal. Putting into forward, at dock, temp will slowly rise after 10 mins or so but only to 162/163. Pulling back to neutral the temp remains above 160.
Checking engine after, the anti freeze level is at the top of manifold but the burp box is down.
Engine hours 960, heat exchange cleaned at 750/800.
I am beyond my level of competence and understanding. Suggestions???

Carl Beckmann
Palmetto Moon # 223
KevinMc
Posts: 85
Joined: Sun Sep 08, 2013 5:36 am

Re: Engine overheating

Post by KevinMc »

I was having a similar issue and some cavitation at low speed. Temp would rise to close to 200 at full throttle and speed would barely make it over 5 knots.

When the boat was pulled this spring for hull painting, etc. I had about 2 feet of line wrapped around the shaft. It was the cause of the decrease in speed, increase in temp and was the cause of the cavitation. The line wasn't catching on anything, it was just wrapped around the shaft. We are back in the water and everything is fine. Steady temp, no cavitation, 6 plus at 2200rpm.
Kevin
#59
NavSta Norfolk Marina
R.B.
Posts: 233
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Location: Ontario, Canada

Re: Engine overheating

Post by R.B. »

Take a laser temp reader, and check your temps at idle and when running at higher RPMs to see if the temp increase is actually there. If it isn't it is probably electrical, look at temp sensor, temp gauge and clean contact points. If the temp does rise, it is probably mechanical, a blockage some where. Recheck your water pump, intake strainer, heat exchanger, etc.
Ralph

WOLFHELM
C350 #342
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russp
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Re: Engine overheating

Post by russp »

More questions re engine overheating before I start pulling stuff apart. Heat exchanger pulled down and cleaned about a year ago, raw water intake clear, new raw water pump, flow out exhaust looks normal, coolant in header and reservoir, belt not slipping, but.....
  • temp rises to 160 and sits there if I cruise up to 1800 rpm (about 5 knots)
    as I go to higher and higher revs temp rises steadily
    at 2600 revs it was going through 200 and I had to cut back
    at 1800 revs "slowly" dropped back to 162 degrees and sat there
Obvious answer is insufficient heat exchange in the raw water/coolant exchanger, has anyone had a problem with the coolant pump before I start pulling the system apart? I would have expected it would last forever in that environment, bearing feels fine.

One maybe relevant factor, the hot water tank takes much longer to heat up when running engine than it did when new, which would also be consistent with reduced coolant pressure/flowrate.

Any thoughts welcome before I get covered in the red stuff!

Russ
Russ Peel
Avalon #150
leigh weiss
Posts: 208
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Re: Engine overheating

Post by leigh weiss »

Russ,
I assume you checked and replaced the sea water impeller in the raw water pump. The other suggestion would be to check that you have bled the hot water loop to the hot water heater. The bleed cock is located on the hose on the bottom of the heater. Small amount of air in the line might cause this problem. Has the coolant level in the expansion tank changed or have you noticed any leaks?
Good luck with your quest, and keep us posted.
Leigh and Donna Weiss
Brisa #155
Georgetown, MD. USA
KevinMc
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Re: Engine overheating

Post by KevinMc »

I had a higher than normal temp at speed last summer. I discovered when the boat was pulled in the spring there was a few feet of crab pot line wrapped around the shaft. That was enough to increase drag on the shaft, slow speed and an very inefficient prop.

On the way down the ICW this year I would get some days where the temp was just higher. Usually we run around 170 but some days we were running 185-190. No idea why it ran higher. The next day we were back to 170.
Kevin
#59
NavSta Norfolk Marina
pdenoncourt
Posts: 36
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Location: Jacksonville, FL

Re: Engine overheating

Post by pdenoncourt »

Russ, I didn't see any mention of your thermostat. You might want to check/replace that item before doing any major surgery.
Regards, Peter Denoncourt
Kite, #72
sv.divine.grace
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Joined: Sat Oct 01, 2016 3:22 pm

Re: Engine overheating

Post by sv.divine.grace »

I had a similar problem once. I thought the raw water impeller needed to be replaced. When I went to shut the raw water intake valve I discovered the raw water strainer was leaking water. However when the engine was running air was being sucked into the raw water system resulting in insufficient cooling. I tightened the lid on the strainer which fixed the problem. Just something to check.
Chips Ahoy!
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Location: Staten Island (Great Kills Harbor), NY

Re: Engine overheating

Post by Chips Ahoy! »

Makes no sense that when you rev down the temp drops.
She's either overheating or not.

I had an erratic temp reading...made me turn back a few times.
No steam coming out of the exhaust and plenty of happy badooshing.

The gauge would ramp up and peg over sometimes.
Had an IR temperature gun on board...engine temp was fine while the gauge at the pedestal was scaring me.
Checked the connection and sender...didn't help.

Swapped out the gauge ..life is good.

I'm a big fan of IR Temp guns as a "truth test" vs gauges "alternative facts".

-g
-george pringle
Chips Ahoy! #232
Staten Island (Great Kills Harbor), NY
KenKrawford
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Location: Atlanta, GA

Re: Engine overheating

Post by KenKrawford »

I had a situation similar to what Russ is experiencing but the rise in temperature only occurred when towing a dink or running in the 2800-2900 RPM range. If I decreased engine RPM's to 23-2400 the temp would drop back down. It turned out the vanes on the raw water impeller were cracked but still intact. A new impeller solved the problem.

Chips Ahoy! wrote:Makes no sense that when you rev down the temp drops.
She's either overheating or not.

I had an erratic temp reading...made me turn back a few times.
No steam coming out of the exhaust and plenty of happy badooshing.

The gauge would ramp up and peg over sometimes.
Had an IR temperature gun on board...engine temp was fine while the gauge at the pedestal was scaring me.
Checked the connection and sender...didn't help.

Swapped out the gauge ..life is good.

I'm a big fan of IR Temp guns as a "truth test" vs gauges "alternative facts".

-g
Ken Krawford
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C350 # 351
Lake Lanier, GA
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bibbjs
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Re: Engine overheating

Post by bibbjs »

Chips Ahoy! wrote:Makes no sense that when you rev down the temp drops.
She's either overheating or not.

I had an erratic temp reading...made me turn back a few times.
No steam coming out of the exhaust and plenty of happy badooshing.

The gauge would ramp up and peg over sometimes.
Had an IR temperature gun on board...engine temp was fine while the gauge at the pedestal was scaring me.
Checked the connection and sender...didn't help.

Swapped out the gauge ..life is good.

I'm a big fan of IR Temp guns as a "truth test" vs gauges "alternative facts".

-g
I have to disagree...There are a number of reasons why decreasing RPM would cause the temp to drop into normal operating levels. Remember that heat load increases roughly with the square of the engine load. In a fixed prop boat engine system, the engine load can be directly related to the RPM when in gear.

I think the main things I would look at are (hopefully starting with simpler first):

1) Is there reasonable water flow out of the exhaust?
2) Is there an air leak in the water suction side (between the intake and the water pump)
3) Is there sufficient coolant in the engine block?

The key is to isolate which part of the cooling system is not performing up to spec. Note as well that the flow tests can be done in neutral at speed - reducing the potential to overheat while testing.

So, low water flow can be traced to an obstruction upstream of the pump, an obstruction in the heat exchanger clogged intake strainer, barnacle in the thru hull, or a failing pump. Arguably an air leak could also show up as low water flow. I am not sure how aerated the water would appear in this case (glycol gets cloudy with air bubbles, water not so much).

Obviously low coolant will decrease system performance and is easily fixed.

If none of these seem to be the issue, then you are probably seeing poor heat exchanger performance.

Good luck!!
J. Bibb
Magick Dragon (formerly Snooze Time)
Hull #45
nybor
Posts: 248
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Re: Engine overheating

Post by nybor »

one of the respondents mentioned the thermostat. Mine overheated at high rpm and temp went down concomitant with rpm.
I replaced the thermostat (extremely easy) and perfect for years to date........(again, very dangerous to say things like that!)


dave
SeaBreeze
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Re: Engine overheating

Post by SeaBreeze »

To Palmetto Moon
Carl
If you have not found a solution based on the info provided by others, I have a suggestion. Your over heating at 2k + revs then returning to normal temps when you reduce revs could be related to an overloaded engine. Maybe something wrapped around the prop shaft, fouled prop or just the load created by powering into the seas created by those 30-40k winds? Did you notice exhaust smoke while the engine temp was elevated or was it too windy to notice? Dos the temp go up if you rev up at the dock while in neutral?
Hope you find a low or no cost solution.
Rick
Sea Breeze
Rick Parish
Sea Breeze
yodagwb
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Re: Engine overheating

Post by yodagwb »

I have one of the older Universal M35B. They are designed to cruise at 2000-2400 rpms. The engine operating temp is between 170 and190 degrees, prolonged lower or higher not so good. Mine is starting to run a bit hotter than normal, 175. Upon doing some research turns out one is suppose to clean or have cleaned the heat exchanger every 1000 hours. Who knew. On my list when I get to my marina. Till then just going to back the rooms down a bit and baby it.

Ps impeller is new, strainers are clean and the coolant has recently been changed.
JohnNorton
Posts: 59
Joined: Thu Oct 13, 2011 12:27 pm

Re: Engine overheating

Post by JohnNorton »

So here is what I did: Took off both end caps; checked the starboard end for old, broken off pieces of zincs, removing what I found; untwisted a wire coat hanger (the short pigtail fit just right inside the tubes) and reamed out each tube. I did not remove the exchanger from the boat. Engine runs at 162 degrees, has for the past two years following this procedure.
The concern for any possible weak areas had me do this carefully, gently.- John, hull 209
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russp
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Location: Paynesville, Australia

Re: Engine overheating

Post by russp »

Hey Rick, thanks for your piece of wisdom because might apply to me! I know my prop is currently overpitched (because I forgot to repitch it while out last time!, and intend to do it next lift out). Consequently the engine is overloaded over about 2300 rpm at present, does blow black smoke, and is when temp starts rising, so it might all go away when I repitch and get back to WOT of about 3000 rpm.

Russ
Avalon #150
SeaBreeze wrote: Tue Feb 21, 2017 7:16 pm To Palmetto Moon
Carl
If you have not found a solution based on the info provided by others, I have a suggestion. Your over heating at 2k + revs then returning to normal temps when you reduce revs could be related to an overloaded engine. Maybe something wrapped around the prop shaft, fouled prop or just the load created by powering into the seas created by those 30-40k winds? Did you notice exhaust smoke while the engine temp was elevated or was it too windy to notice? Dos the temp go up if you rev up at the dock while in neutral?
Hope you find a low or no cost solution.
Rick
Sea Breeze
Russ Peel
Avalon #150
jmcbraye@hotmail.com
Posts: 14
Joined: Wed Feb 20, 2013 11:22 am
Location: Fort Lauderdale

Re: Engine overheating

Post by jmcbraye@hotmail.com »

Ahoy all - I've been having major overheating problems. The high temp alarm has gone off several times even at lower RPM. I shut it down right away of course and let the engine cool. I've checked the coolent level, impeller, exhaust exhaust elbow, pulled hoses and looked for flow blockages. Can't find anything except the raw water flow from the through hull to the water strainer box seems to be very restricted and seems like little more than a trickle.
Maybe a blocked through hull opening? Does anyone know what the normal flow rate would look like if you just opened the through hull and sea strainer? Thanks in advance. Love this forum!
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