Over heating at low RPM's
 

I have a 350 with an Alpha 1 that is overheating at low rpms. Diagnosing
the same problem last year, I had to have the water pump in the lower unit
replaced. I will troubleshoot all other possibilities this weekend before
having to pull the boat out, but thought you folks in the news groups may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

Sorry I don't have the reference, but 3 years or so is the "recommended"
impeller replacement schedule. And that I think is based on a 100 hours or
so season. I also understand that the newer impellers are built to last
longer. My approach ... pull the outdrive every 3 seasons to lube the
u-joints etc, and while it's off replace the impeller. And then there are
people run their boats 10 years with no preventive maintenance and have no
problems :-)

"Mark" wrote in message
sgroups.com...
I have a 350 with an Alpha 1 that is overheating at low rpms. Diagnosing
the same problem last year, I had to have the water pump in the lower unit
replaced. I will troubleshoot all other possibilities this weekend
before
having to pull the boat out, but thought you folks in the news groups may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

Oops ... I read "water pump" as the engine water pump, not impeller. If it
was me, I'd pull the boat out and hook up the muffs and garden hose. Could
be someone started the engine up with no water supply ... that burns out the
impeller. Or could be the engine water pump, or risers blocked, or
thermostat, or .... could even be a faulty temperature gauge. Anyway,
running it on the garden hose should give some insight into the problem.

Agreed on the engine pump, this is the most typical cause of low RPM over
heating and OK at higher. It isn't a displacement pump like the one on the
drive, it is a centrifugal pump and as it ages, the vanes corrode off, they
simply don't sling any water at low speeds then. End result is lots of
water from driver pump, however it isn't circulated through the block, it
just get poured out the exhaust. The engine pump is responsible to move it
through the block and heads.

Common issue on cars with high mileage also, overheat at idle, OK if revved
up a bit..

Greg

"Bowgus" wrote in message
...
Oops ... I read "water pump" as the engine water pump, not impeller. If
it
was me, I'd pull the boat out and hook up the muffs and garden hose. Could
be someone started the engine up with no water supply ... that burns out
the
impeller. Or could be the engine water pump, or risers blocked, or
thermostat, or .... could even be a faulty temperature gauge. Anyway,
running it on the garden hose should give some insight into the problem.

You don't say whether you operate in fresh or salt water, or whether your
engine has fresh water w/anti-freeze circulating coolant (w/ heat
exchanger). Esp if it's operated in salt water, on a '86 boat, I'd bet on
the riser being clogged. Pull it and have a look -- you'll need new gaskets
when making replacement. You can "rod it out" or have a radiator shop give
it an acid cleaning -- either will give you just one or two seasons more.
Usually better to buy new if you intend to keep the boat.

First choice would have been lower unit pump impeller, but that's fairly
new -- unless it was later run dry and damaged. Impellers should be changed
every three years or so for normal recreational boats. The rubber gets stiff
with age and they lose efficiency. In water with lots of silt and
particulates, esp frequent shallow water operation, they can wear out faster
due to abrasion. Same for the metal contact surface in the pump --
inspection will tell if that (or more likely) the whole pump needs replaced.

Good luck,
Len

Eliminate "ns" for email address.

--
"Mark" wrote in message
sgroups.com...
I have a 350 with an Alpha 1 that is overheating at low rpms. Diagnosing
the same problem last year, I had to have the water pump in the lower unit
replaced. I will troubleshoot all other possibilities this weekend
before
having to pull the boat out, but thought you folks in the news groups may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

On Fri, 3 Jun 2005 07:37:16 -0400, "Mark"
wrote:

I have a 350 with an Alpha 1 that is overheating at low rpms.

Dont worry about it, its probably the gauge.

Me and the wife
http://pg.photos.yahoo.com/ph/harkra...bum?.dir=/1323

Harry.Krause wrote:
On Fri, 3 Jun 2005 07:37:16 -0400, "Mark"
wrote:


I have a 350 with an Alpha 1 that is overheating at low rpms.


Dont worry about it, its probably the gauge.

Me and the wife
http://pg.photos.yahoo.com/ph/harkra...bum?.dir=/1323


You really shouldn't give out silly advice and credit it to another
poster. It could cause some unsuspecting poster substantial money.

I am running in fresh water (St. Lawrence 1000 Islands area) and it is not a
closed system (no antifreeze). My boating habits rarely take me into silty
/ dirty water, but maybe the zebra mussels that have invaded the area and
cleaned up the water have managed to get hold of my system. I have never
run the boat dry and do not even turn the engine over without muffs on.
Another boating friend insists it is the pump in the outdrive that is the
trouble and has offerred to assist changing it this time.

The reason I am suspecting the outdrive pump is the "so called" mechanic
that replaced it for me last year somehow managed to reassemble the drive
without a spacer / washer that can fall out when the drive is split. That
washer missing caused no symtoms for about a month or two and then
periodically caused an inability to shift. I contacted a more reputable
mechanic and he diagnosed the problem for me over the phone and had my boat
fixed back up the same day.

Some great feedback and suggestions everyone.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

"Len Krauss" wrote in message
...
You don't say whether you operate in fresh or salt water, or whether your
engine has fresh water w/anti-freeze circulating coolant (w/ heat
exchanger). Esp if it's operated in salt water, on a '86 boat, I'd bet on
the riser being clogged. Pull it and have a look -- you'll need new
gaskets
when making replacement. You can "rod it out" or have a radiator shop give
it an acid cleaning -- either will give you just one or two seasons more.
Usually better to buy new if you intend to keep the boat.

First choice would have been lower unit pump impeller, but that's fairly
new -- unless it was later run dry and damaged. Impellers should be
changed
every three years or so for normal recreational boats. The rubber gets
stiff
with age and they lose efficiency. In water with lots of silt and
particulates, esp frequent shallow water operation, they can wear out
faster
due to abrasion. Same for the metal contact surface in the pump --
inspection will tell if that (or more likely) the whole pump needs
replaced.

Good luck,
Len

Eliminate "ns" for email address.

--
"Mark" wrote in message
sgroups.com...
I have a 350 with an Alpha 1 that is overheating at low rpms.
Diagnosing
the same problem last year, I had to have the water pump in the lower
unit
replaced. I will troubleshoot all other possibilities this weekend
before
having to pull the boat out, but thought you folks in the news groups may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the
engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

I am making progress with my over heating problem! Getting ready to pull
the boat to change the outdrive impeller, the folks at Gilbert Marine in
Brockville suggested I try pulling the hose going into the housing near the
thermostat (coming from the outdrive) and run the engine just long enough to
see if and how much water the impeller is pushing up. Estimating maybe a
gallon in 5 to 10 seconds, I felt that should be sufficient and moved onto
the next possibility (and much easier than splitting the outdrive to change
the water pump). I removed the t'stat and ran the engine at idle and
higher rpms and the temperature never went over 135 (normally operates
around 145 to 150). I am going to try it this weekend with no thermostat
and see what happens. Stay tuned ...

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm (link to the company website describing my
accessory hooks for boats)


"Mark" wrote in message
sgroups.com...
I am running in fresh water (St. Lawrence 1000 Islands area) and it is not
a closed system (no antifreeze). My boating habits rarely take me into
silty / dirty water, but maybe the zebra mussels that have invaded the area
and cleaned up the water have managed to get hold of my system. I have
never run the boat dry and do not even turn the engine over without muffs
on. Another boating friend insists it is the pump in the outdrive that is
the trouble and has offerred to assist changing it this time.

The reason I am suspecting the outdrive pump is the "so called" mechanic
that replaced it for me last year somehow managed to reassemble the drive
without a spacer / washer that can fall out when the drive is split.
That washer missing caused no symtoms for about a month or two and then
periodically caused an inability to shift. I contacted a more reputable
mechanic and he diagnosed the problem for me over the phone and had my
boat fixed back up the same day.

Some great feedback and suggestions everyone.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

"Len Krauss" wrote in message
...
You don't say whether you operate in fresh or salt water, or whether your
engine has fresh water w/anti-freeze circulating coolant (w/ heat
exchanger). Esp if it's operated in salt water, on a '86 boat, I'd bet
on
the riser being clogged. Pull it and have a look -- you'll need new
gaskets
when making replacement. You can "rod it out" or have a radiator shop
give
it an acid cleaning -- either will give you just one or two seasons more.
Usually better to buy new if you intend to keep the boat.

First choice would have been lower unit pump impeller, but that's fairly
new -- unless it was later run dry and damaged. Impellers should be
changed
every three years or so for normal recreational boats. The rubber gets
stiff
with age and they lose efficiency. In water with lots of silt and
particulates, esp frequent shallow water operation, they can wear out
faster
due to abrasion. Same for the metal contact surface in the pump --
inspection will tell if that (or more likely) the whole pump needs
replaced.

Good luck,
Len

Eliminate "ns" for email address.

--
"Mark" wrote in message
sgroups.com...
I have a 350 with an Alpha 1 that is overheating at low rpms. Diagnosing
the same problem last year, I had to have the water pump in the lower
unit
replaced. I will troubleshoot all other possibilities this weekend
before
having to pull the boat out, but thought you folks in the news groups
may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the
engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

A suggestion ... don't run the engine very long without a thermostat ...
even better, don't run without a thermostat at all. One of the thermostat's
function I've been told is to ensure a relatively consistent engine
temperature preventing parts warp etc.. Having said that, I had a thermostat
fail closed on a Toyota. I removed it and drove home from ... interestingly
enough Johnstown near where you're at ... to Ottawa without any apparent
problems.

I am going to try it this weekend with no thermostat and see what
happens. Stay tuned ...

Only problem w/ running an engine w/out a thermostat is you may never warm
the engine to proper temp and you may find the engine running rich all the
time. This will cost you in fuel but won't hurt the engine (except for
possibly carbon buildup over a long time).

Won't hurt in terms of overheat as the max coolant is flowing all the time.
If the engine overheats and warps something in this condition it would
really overheat w/ a thermostat installed as a fully open thermostat adds a
certain amount of restriction just due to the metal parts being there.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Bowgus" wrote in message
...
A suggestion ... don't run the engine very long without a thermostat ...
even better, don't run without a thermostat at all. One of the
thermostat's
function I've been told is to ensure a relatively consistent engine
temperature preventing parts warp etc.. Having said that, I had a
thermostat
fail closed on a Toyota. I removed it and drove home from ...
interestingly
enough Johnstown near where you're at ... to Ottawa without any apparent
problems.

I am going to try it this weekend with no thermostat and see what
happens. Stay tuned ...

You can run the engine without a thermostat, but it never gets up to normal
operating temperature and you get lots more wear, and worse fuel economy. I
have had a thermostat stick open, winter time returning from Tahoe. No car
problem, except for ice on the inside the windows, and we and the daughters,
had on most of out heavy ski clothes.

"Bowgus" wrote in message
...
A suggestion ... don't run the engine very long without a thermostat ...
even better, don't run without a thermostat at all. One of the
thermostat's
function I've been told is to ensure a relatively consistent engine
temperature preventing parts warp etc.. Having said that, I had a
thermostat
fail closed on a Toyota. I removed it and drove home from ...
interestingly
enough Johnstown near where you're at ... to Ottawa without any apparent
problems.

I am going to try it this weekend with no thermostat and see what
happens. Stay tuned ...

It's not "overheat" or "underheat" ... it's "uneven heat" that (I was told)
may cause a problem ... it's ... one part of the engine is hot and one part
of the engine is cold(er) than it should be because of the lack of
temperature regulation provided by the thermostat. I myself will run my
engines with the thermostat installed ... you guys can do (obviously) as you
like :-)

OT: My mercruiser thermostat is 140 F ... I myself find that unususual
compared to an auto thermostat. My understanding ... an auto engine is most
efficient around 235 F (achievable because the sytem is pressurized). So ...
why the low temp for the marine (version) engine?

"tony thomas" wrote in message
news:Dz5qe.31276$x96.130@attbi_s72...
Only problem w/ running an engine w/out a thermostat is you may never warm
the engine to proper temp and you may find the engine running rich all the
time. This will cost you in fuel but won't hurt the engine (except for
possibly carbon buildup over a long time).

Won't hurt in terms of overheat as the max coolant is flowing all the
time.
If the engine overheats and warps something in this condition it would
really overheat w/ a thermostat installed as a fully open thermostat adds
a
certain amount of restriction just due to the metal parts being there.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Bowgus" wrote in message
...
A suggestion ... don't run the engine very long without a thermostat ...
even better, don't run without a thermostat at all. One of the
thermostat's
function I've been told is to ensure a relatively consistent engine
temperature preventing parts warp etc.. Having said that, I had a
thermostat
fail closed on a Toyota. I removed it and drove home from ...
interestingly
enough Johnstown near where you're at ... to Ottawa without any apparent
problems.

I am going to try it this weekend with no thermostat and see what
happens. Stay tuned ...

About the 140 F ... could it be because the manufacturer realizes that a
lotta boaters run their boats at WOT (= heat) ... whereas most :-) auto
drivers don't?

OT: had the boat out first time this year ... ran just fine ... an excellent
day out. Too bad the weekend is not looking good ... we're looking forward
to trailering down to Ivy Lea for the up to Gananoque, across and down the
US side, around the castle, back to Ivy Lea loop ... and the islands just
off Gananoque ... very nice.

"Bowgus" wrote in message
...
It's not "overheat" or "underheat" ... it's "uneven heat" that (I was
told)
may cause a problem ... it's ... one part of the engine is hot and one
part
of the engine is cold(er) than it should be because of the lack of
temperature regulation provided by the thermostat. I myself will run my
engines with the thermostat installed ... you guys can do (obviously) as
you
like :-)

OT: My mercruiser thermostat is 140 F ... I myself find that unususual
compared to an auto thermostat. My understanding ... an auto engine is
most
efficient around 235 F (achievable because the sytem is pressurized). So
....
why the low temp for the marine (version) engine?

"tony thomas" wrote in message
news:Dz5qe.31276$x96.130@attbi_s72...
Only problem w/ running an engine w/out a thermostat is you may never
warm
the engine to proper temp and you may find the engine running rich all
the
time. This will cost you in fuel but won't hurt the engine (except for
possibly carbon buildup over a long time).

Won't hurt in terms of overheat as the max coolant is flowing all the
time.
If the engine overheats and warps something in this condition it would
really overheat w/ a thermostat installed as a fully open thermostat
adds
a
certain amount of restriction just due to the metal parts being there.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Bowgus" wrote in message
...
A suggestion ... don't run the engine very long without a thermostat
....
even better, don't run without a thermostat at all. One of the
thermostat's
function I've been told is to ensure a relatively consistent engine
temperature preventing parts warp etc.. Having said that, I had a
thermostat
fail closed on a Toyota. I removed it and drove home from ...
interestingly
enough Johnstown near where you're at ... to Ottawa without any
apparent
problems.

I am going to try it this weekend with no thermostat and see what
happens. Stay tuned ...

Just remembered ... here's my old beater under "Bowgus"
http://thebayguide.com/rec.boats/ ... if you should spot me down there in
the 1000 Islands, gimme a shout :-)

Don't forget on a closed (rad) system with antifreeze the boiling point is
substantially higher then raw water and no pressure. Also, most carb based
cars ran 165's, wasn't until injection and pollution controls that the
higher 185's etc came in. One trick to make more power from an injected
engine is to run a 165 thermo and reprogram the computer to except that as
'closed loop' meaning fully warmed up. But it raises pollution. A boat
could run as high as a 165, but to go to a 185 (with typical 10% variance)
pushes it way to close to that magic 212 . Also, in an engine with a 165,
areas around the heads can run up another 20d without the thermostat seeing
that, thus the safety range.


Mark, if the thermostat proves to be the culprit, don't run without it,
replace it, they are only 8 bucks for a Chev and help not just mileage but
lubrication and so on. Also pistons and other critical parts are sized to
work best at a certain temperature.. Don't skip looking at the engine pump
as I suggested a while back. If it is worn, the added restriction of a
thermostat will cause your problem, removing that restriction isn't a fix,
getting a pump that circulates the water correctly is. Look to the
automotive side for the pump, same part (don't do so for starters,
alternators etc, but pump is the same)..

Greg


"Bowgus" wrote in message
...
About the 140 F ... could it be because the manufacturer realizes that a
lotta boaters run their boats at WOT (= heat) ... whereas most :-) auto
drivers don't?

OT: had the boat out first time this year ... ran just fine ... an
excellent
day out. Too bad the weekend is not looking good ... we're looking forward
to trailering down to Ivy Lea for the up to Gananoque, across and down the
US side, around the castle, back to Ivy Lea loop ... and the islands just
off Gananoque ... very nice.

"Bowgus" wrote in message
...
It's not "overheat" or "underheat" ... it's "uneven heat" that (I was
told)
may cause a problem ... it's ... one part of the engine is hot and one
part
of the engine is cold(er) than it should be because of the lack of
temperature regulation provided by the thermostat. I myself will run my
engines with the thermostat installed ... you guys can do (obviously) as
you
like :-)

OT: My mercruiser thermostat is 140 F ... I myself find that unususual
compared to an auto thermostat. My understanding ... an auto engine is
most
efficient around 235 F (achievable because the sytem is pressurized). So
...
why the low temp for the marine (version) engine?

"tony thomas" wrote in message
news:Dz5qe.31276$x96.130@attbi_s72...
Only problem w/ running an engine w/out a thermostat is you may never
warm
the engine to proper temp and you may find the engine running rich all
the
time. This will cost you in fuel but won't hurt the engine (except
for
possibly carbon buildup over a long time).

Won't hurt in terms of overheat as the max coolant is flowing all the
time.
If the engine overheats and warps something in this condition it would
really overheat w/ a thermostat installed as a fully open thermostat
adds
a
certain amount of restriction just due to the metal parts being there.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Bowgus" wrote in message
...
A suggestion ... don't run the engine very long without a thermostat
...
even better, don't run without a thermostat at all. One of the
thermostat's
function I've been told is to ensure a relatively consistent engine
temperature preventing parts warp etc.. Having said that, I had a
thermostat
fail closed on a Toyota. I removed it and drove home from ...
interestingly
enough Johnstown near where you're at ... to Ottawa without any
apparent
problems.

I am going to try it this weekend with no thermostat and see what
happens. Stay tuned ...

"Bowgus" wrote in message
...
It's not "overheat" or "underheat" ... it's "uneven heat" that (I was
told)
may cause a problem ... it's ... one part of the engine is hot and one
part
of the engine is cold(er) than it should be because of the lack of
temperature regulation provided by the thermostat. I myself will run my
engines with the thermostat installed ... you guys can do (obviously) as
you
like :-)

OT: My mercruiser thermostat is 140 F ... I myself find that unususual
compared to an auto thermostat. My understanding ... an auto engine is
most
efficient around 235 F (achievable because the sytem is pressurized). So
...
why the low temp for the marine (version) engine?


Because if a raw water cooled boat engine is run in salt water, then the
salt will precipitate out and plug up the engine cooling passages at about
160 degrees. So they run a 140 as standard. My carbed 351W closed cooling
ran a 160 thermostat. Do not know what the new 350 mpi runs.

Yes ... just after I posted, the light went on that my raw water cooled boat
system is not a closed (pressurized) cooling system ...


Don't forget on a closed (rad) system with antifreeze the boiling point is
substantially higher then raw water and no pressure. Also, most carb
based
cars ran 165's, wasn't until injection and pollution controls that the
higher 185's etc came in.

Good info ... thanks

OT: My mercruiser thermostat is 140 F

Because if a raw water cooled boat engine is run in salt water, then the
salt will precipitate out and plug up the engine cooling passages at about
160 degrees. So they run a 140 as standard. My carbed 351W closed
cooling
ran a 160 thermostat. Do not know what the new 350 mpi runs.

Contrary to some (and maybe good) recommendations, I ran for a bit with no
t'stat. Temperature varied upwards to 130 max depending on the rpm's,
load, etc. Given I used to run normally from 145 to 165 (various
conditions) I made an executive decision and bought a new t'stat and
installed it. The engine temperature is now varying from 145 to 170. It
is maybe 5 degrees higher than what I normally run/range (and the water is
still quite cold, too cold for swimming (for me)), but I can now pull into a
dock without the temperature going 200 (gauge limit) and having to go into
neutral to rev. it up and cool it back down. I think the problem is now
(hopefully or sort of) fixed, but I will be keeping a very close eye on it.
There was a bit of crud laying on the old t'stat when I pulled it out, so
maybe dirt was impeding the reliability of it opening, and/or maybe there is
still another problem such as the outdrive water pump getting weak.

Some great feedback and suggestions again everyone. Thank you. Should any
new news develop, I will make sure I let everyone know.

Bowgus, If you are doing the run from Boldt Castle back to Gan, make sure
you do the Riff. It is a very samll passage between the Lake o' the Isle,
going under the bridge between the US and Canadian Customs, and exiting into
the Cdn channel near Ivy Lea. Other than the one boat width passage in
some areas, the only other area you need to be careful around is the bottom
end just off Lake o the Isle. I have a 268 Searay (YesDear) and can
manouvre it through no problem, but would not take much larger of a boat
through though.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

"Bowgus" wrote in message
...
About the 140 F ... could it be because the manufacturer realizes that a
lotta boaters run their boats at WOT (= heat) ... whereas most :-) auto
drivers don't?

OT: had the boat out first time this year ... ran just fine ... an
excellent
day out. Too bad the weekend is not looking good ... we're looking forward
to trailering down to Ivy Lea for the up to Gananoque, across and down the
US side, around the castle, back to Ivy Lea loop ... and the islands just
off Gananoque ... very nice.

"Bowgus" wrote in message
...
It's not "overheat" or "underheat" ... it's "uneven heat" that (I was
told)
may cause a problem ... it's ... one part of the engine is hot and one
part
of the engine is cold(er) than it should be because of the lack of
temperature regulation provided by the thermostat. I myself will run my
engines with the thermostat installed ... you guys can do (obviously) as
you
like :-)

OT: My mercruiser thermostat is 140 F ... I myself find that unususual
compared to an auto thermostat. My understanding ... an auto engine is
most
efficient around 235 F (achievable because the sytem is pressurized). So
...
why the low temp for the marine (version) engine?

"tony thomas" wrote in message
news:Dz5qe.31276$x96.130@attbi_s72...
Only problem w/ running an engine w/out a thermostat is you may never
warm
the engine to proper temp and you may find the engine running rich all
the
time. This will cost you in fuel but won't hurt the engine (except for
possibly carbon buildup over a long time).

Won't hurt in terms of overheat as the max coolant is flowing all the
time.
If the engine overheats and warps something in this condition it would
really overheat w/ a thermostat installed as a fully open thermostat
adds
a
certain amount of restriction just due to the metal parts being there.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Bowgus" wrote in message
...
A suggestion ... don't run the engine very long without a thermostat
...
even better, don't run without a thermostat at all. One of the
thermostat's
function I've been told is to ensure a relatively consistent engine
temperature preventing parts warp etc.. Having said that, I had a
thermostat
fail closed on a Toyota. I removed it and drove home from ...
interestingly
enough Johnstown near where you're at ... to Ottawa without any
apparent
problems.

I am going to try it this weekend with no thermostat and see what
happens. Stay tuned ...

Update on my Volvo AQ240A/280 over heating problems:

Pulled the manifolds, heat exchanger, and heads last Sunday and took them to
town on Monday.

The exhaust manifolds and risers were in pretty good shape except for some
external rust. They got hot tanked in a 3 dip program and came out in good
shape.

The heat exchanger turned out to be plugged with some seaweed. They hot
tanked it and cleaned out the tubes - they also found a small leak at the
filler neck and fixed that.

By next week, I should have everything back together and running strong.

"Jim Pook" wrote in
:

By next week, I should have everything back together and running strong.



Well? What time to you want us at the dock? We'll help you sea trial it
and watch the guages. We'll bring the beer....

--
Larry

You know you've had a rough night when you wake up and your outlined in
chalk.