The last thread about this got me poking around. On my Perkins 4-108 1979 in
a 1980 Endeavour sloop the coolant tank sits on the thermostat and is hosed
into the exhaust manifold. Off the exhaust manifold runs a hose to the water
heater. The hose back from the water heater tees into the aft end of the
oil/transmission heat exchanger. I am having some overheating problems and
would like to try bypassing the water heater. Do I need to keep this loop
flowing or can I clamp it off? Will clamping force more water thru the
engine?
Thanks to everyone - Allen

"bushman" wrote in
m:

Thanks to everyone - Allen

Change the impeller in the water pump first to make sure this isn't the
problem. If that doesn't fix it, then....

Take the heat exchanger to a radiator shop and have it cleaned.....
Replace the zincs when you put it back.

Wishing it wasn't so isn't gonna fix it....sorry.

Cleaning our 4-108's heat exchanger dropped the 200F at 2200 RPM down to
just barely opening the NEW thermostat! It's like getting a new
engine...(c;

Don't forget to flush the closed loop coolant side like a car before you do
the heat exchanger. Might as well clean the block out, too....

Gook came out of ours something awful....

--
Larry

Done so far:
Prop clean
Hull clean
Thru-hull clean & clear
Strainer clean
Hoses apart and clean
Rebuilt pump with new impeller
Heat exchanger clean and shiny
New thermostat (tested)
Flushed coolant Came out clean
New radiator cap (tested)
Added coolant resevour

I am interested in mickey's bypass he has for the water heater and how it is
plumbed. I think I want to be able to isolate the water heater anyway.

Next: Exhaust manifold to talepipe comes out.

Thanks again - Allen

how did you clean the heat exchanger? I've heard anything up to and
including muriatic acid. How old is you exchanger? A new exchanger for
about $150 may be an investment, at least so you can keep your old one
as a spare, but first try to see if you can get good water flow through
it.

Email me directly about the bypass,p lease, and I'll try to send you
pics.

cheers
mickey

I took the heat exchanger off with the intent of sending it to the radiator
shop but it was very clean and all tubes were clear so I gave it a quick
bath in some phosphoric (?) acid I had on hand. It came out very shiny. I
capped the ends and pumped in some air pressure let it sit over night for
each side to check for leaks. I would like to have a spare if you know of a
good used one.
-Allen

"bushman" wrote in
m:

Thanks again - Allen



Armed with all this new information, let me ask you how bad does it smoke?
Black or white smoke?

You've eliminated all the cooling system problems I know of in this simple
diesel. Now, I'm wondering if you don't have an injection issue or an
overloading problem....

I assume this prop used to work fine and didn't overheat the engine, right?
Has anyone been under the boat to see how bad the prop is fouled?

When you rev it up with the transmission disengaged, does it rev up much
better than when it's engaged?

An observation we all made after Cutter Doc in Daytona worked on the
injectors was how much COOLER the engine ran. I'm talking about 30 degrees
cooler! All that was done was to fix the injectors, besides getting the
seawater out of it. It still just opens the thermostat even if you run it
wide open throttle! Does yours seem to knock harder than usual, an
indication of bad spray pattern on the injector? Has anyone checked the
injection TIMING on the Perkins?

This injector difference also showed up on another friend's Hatteras 56
with twin 8V92TAs in it. One engine ran hotter than the other and the
thermostats had been in it quite a while so I changed them. Didn't change
the problem. I noticed the port engine seemed to labor more than starboard
and ran hotter. The diver said everything under the boat was fine when he
cleaned the Charleston off her. We got a diesel shop to pull the injectors
and take them in to test them. One of the injectors on that port engine
wasn't spraying properly and the TIMING was out of specs! They replaced
the bad injector and reset the timing and the engines sync'd better and
pulled more evenly. Both engine temp guages in the engine room and at the
helms were even after that.

--
Larry

"bushman" wrote in
m:

I am interested in mickey's bypass he has for the water heater and how
it is plumbed. I think I want to be able to isolate the water heater
anyway.



Ours is a T of 3 valves. Two valves shut off the hoses to the water heater
in case it ruptures or a hose fails. The other valve is the bypass valve
across the engine side of the other two valves.

-----------T--V-----------
Engine V Water heater
-----------T--V-----------

I'm not sure the bypass valve across is really necessary. It came on the
boat. All the cooling water can't go through the water heater, just like
all the cooling water in your car doesn't go through your heater
core...same idea. The water heater just bypasses the thermostat and heat
exchanger and I'd think the bypass valve would make the engine run hotter,
not cooler, if the thermostat were normally near open where it couldn't
compensate. Other than when the heater was replaced and moved OUT of the
engine room into the lazerette so we could get to the front of the engine
and belts easier, the valves have never been closed. Maybe I'll fool with
them and see what the effect of shutting down all 3 valves does to engine
temperature some time.

--
Larry

Larry
I've a similar setup, but without the valves from the Tees to the
heater. (I figure if a hose breaks, I could just replumb the existing
hose. Actually, I didn't figure anything--it came that way! I
leave the valve across (the middle in your diagram) open most of the
time. (if it's winter and cold and want some hot water fast, or the
engine is not getting up to temp, I close it, but that's rare.)

It sounds like your valves a little different though--If I had three
valves and shut them all off, then there would be no coolant
circulation on my system or engine. I'm also not sure I understand how
the water heater bypasses the thermostat and heat exchanger. My
coolant runs:

engine - water heater (with bypasses) - heat exchanger

part of my problem is that the wtaer heater hoses are smaller than the
engine hoses, so obviously I need something to give there, thus the
bypass. Here's a diagram: (best viewed with a fixed-width font)

WATER HEATER
: :
: :
engine......____L___/___L____......heat exchanger (to engine)

Of course, the heat exchanger is mounted on the engine, but it's hard
to loop with these text diagrams Here ... and : are hoses, _L_ is
a T and _/_ is a valve. I have no valves between the _L_ and the heat
exchanger.

mickey

"mickey" wrote in
oups.com:

part of my problem is that the wtaer heater hoses are smaller than the
engine hoses, so obviously I need something to give there, thus the
bypass. Here's a diagram: (best viewed with a fixed-width font)

WATER HEATER
: :
: :
engine......____L___/___L____......heat exchanger (to engine)

Of course, the heat exchanger is mounted on the engine, but it's hard
to loop with these text diagrams Here ... and : are hoses, _L_ is
a T and _/_ is a valve. I have no valves between the _L_ and the heat
exchanger.


Are you sure about that? Water hoses and passages are BIG, not the tiny
hoses to the water heater. The heat exchanger is directly on the engine on
the Perkins looks hooked directly to the block passages. I don't think you
have to put a loop hose on it if you don't have a water heater....

That would seem stupid, to me. Water heater hoses should be like car
heater hoses. The engine outlet to the water heater comes from the high-
side of the thermostat, which pressurizes the water to the water heater.
The low side of the water heater return should go into the suction side of
the heat exchanger back into the engine, giving you hot water BEFORE the
thermostat opens.

I don't really remember. I'll look next time I'm in the bilge. I now have
quite a list to look at...(c;

--
Larry

Larry wrote:
"mickey" wrote in
oups.com:

part of my problem is that the wtaer heater hoses are smaller than the
engine hoses, so obviously I need something to give there, thus the
bypass. Here's a diagram: (best viewed with a fixed-width font)

WATER HEATER
: :
: :
engine......____L___/___L____......heat exchanger (to engine)

Of course, the heat exchanger is mounted on the engine, but it's hard
to loop with these text diagrams Here ... and : are hoses, _L_ is
a T and _/_ is a valve. I have no valves between the _L_ and the heat
exchanger.


Are you sure about that? Water hoses and passages are BIG, not the tiny
hoses to the water heater. The heat exchanger is directly on the engine on
the Perkins looks hooked directly to the block passages. I don't think you
have to put a loop hose on it if you don't have a water heater....


Granted it's late, but I don't really get what you're saying so I must
not have made myself clear. The Heat exchanger is on the engine, and
the only reason the loop is there is because of the water heater.

That would seem stupid, to me. Water heater hoses should be like car
heater hoses. The engine outlet to the water heater comes from the high-
side of the thermostat, which pressurizes the water to the water heater.
The low side of the water heater return should go into the suction side of
the heat exchanger back into the engine, giving you hot water BEFORE the
thermostat opens.

Hrm. I'll have to check on how mine is set up. I'll guess your setup
is right. I think mine goes into the suction side of the heat
exchanger, so I probably have the same setup.

mickey