Thermostat ID question.

[Cityhix]

Ericson 29.

I've been overheating at RPMs over about 1400 or so. Changed impellers (FWC) but haven't gone any further.

I decided to open the thermostat housing and found a 1/4" spacer under the housing and a tstat labeled "Wahler 3/5 60 (degree C=140F)". I can't seem to find and info on this tstat. All looked fairly clean under the housing. Any ideas on what I have?

Thanks,

Dylan

[JOHN COOKSON]

Ericson 29.

I've been overheating at RPMs over about 1400 or so. Changed impellers (FWC) but haven't gone any further.

I decided to open the thermostat housing and found a 1/4" spacer under the housing and a tstat labeled "Wahler 3/5 60 (degree C=140F)". I can't seem to find and info on this tstat. All looked fairly clean under the housing. Any ideas on what I have?
Dylan

A couple.
A thermostat that is not opening all the way.
The cooling passages in the engine are so blocked that you are not getting enough water through the engine to cool it adequately.
A partially blocked cooling water inlet.
Blockage somewhere after the engine.
Try running without the thermostat. Try clamping the bypass.
Sorry, don't have info on the thermostat. It sounds like a after market one not the original double action thermostat.

TRUE GRIT

[BunnyPlanet169]

The spacer indicates that some PO replaced the OEM thermostat with an aftermarket thermostat. Aftermarket thermostats require an extra 1/4" to clear the bypass hub inside the thermostat housing. Wahler is a European manufacturer, and the same PO probably crossed the part number to what was available at the FLAPS (friendly local auto parts store).

(You can see MMI offerings here: http://www.moyermarine.com/cgi-bin/s...rebuilder.html)

+ 1 for what John said - it's time to figure out where the blockage is. Run without a thermostat for troubleshooting.

Do you have the same or reduced water flow out the back? We're presuming reduced...

Do you have a bypass loop?

Troubleshooting follows a simple and well trodden path. Many cooling threads to search... By running the engine, or cranking for short periods, monitor the water flow at various places by dumping it into a pail. Full flow is maybe 3- 5 GPM.

Start at the back end where the water leaves the exhaust manifold and heads to the exhaust. Lots of people find crap stuck in the manifold at that point. Replace machined square brass fittings with street elbows if you have room - modest improvements in flow.

Keep working along the water path until you find where the restriction is. Key places: Manifold outlet... thermostat outlet... Pump outlet... Thru-hull outlet... Your problem is just after where the water flows cleanly....

[edwardc]

And don't forget the heat exchanger! The bottom of the raw water side can become clogged with the remains of spent zinc anodes.

[joe_db]

For a FWC engine, I would remove the thermostat, block the bypass hose, and see how you do. You get full flow cooling and see where the issue is. If you still run hotter than desired, you need to improve cooling someplace else in the system.

[Cityhix]

Thanks for the replies, folks. I didn't mean to go silent. I thought I would get email notifications for every reply and didn't check back till now.

At my last check, I ran the motor, in gear, at the dock at around 1600 rpm and the temp gauge settled in at about 185 and remained steady. I understand this to be a bit hotter than "normal". For what it's worth, this is on Puget Sound with the engine hatch off and air temp at about 65 or 70 F.

Future diagnostics/maintenance to be done (not necessarily in this order):

Acid flush
High pressure flush
Check all hoses for blockage
Clean heat exchanger
Check manifold (outlet) for blockage
Check flow rate through system
Remove tstat and block bypass hose and run to assess temp

Just to clarify: the bypass hose runs from the T fitting in the block to thermostat housing. The opening of the thermostat allows coolant to run through the block at the set temp? Blocking the bypass hose forces coolant through the block with the thermostat removed? Installing a ball valve would only be done with the thermostat removed?

Thanks!

BTW: I'm amazed at the level of comfort I've achieved with this motor in the short time I've had it. This thanks to Moyer, this forum and plenty of hours "communing" with the rusty little beast.

[JOHN COOKSON]

Just to clarifyA) the bypass hose runs from the T fitting in the block to thermostat housing.(B) The opening of the thermostat allows coolant to run through the block at the set temp? (C) Blocking the bypass hose forces coolant through the block with the thermostat removed? (D) Installing a ball valve would only be done with the thermostat removed?.

Late model engine:
(A) Yes
(B) A couple of considerations: Just having a thermostat in the flow through the engine will result in less flow through the engine because even when open all the way the thermostat in is the way of the flow somewhat.
Remember the thermostat needs to open and when it does the flow through the bypass needs to be blocked at the same time other wise the coolant will take the path of least resistance around the engine through the bypass. The bypass is just that: it causes the coolant to bypasses going through the engine.This is the idea behind a double action thermostat. Your after market thermostat may not restrict the bypass as it opens. A valve or clamping the bypass will tell the story real quick.
(C) You can use a valve on the bypass with or without a thermostat. I run both a thermostat and a valve on the bypass on my A4.
(D) If you have a single action thermostat you will most likely have to restrict the bypass somehow. A valve on the bypass allows you to balance the flow around the the engine against the flow through through the engine for optimal running temperature with a thermostat or no thermostat.

TRUE GRIT

[Cityhix]

Late model engine:

(D) If you have a single action thermostat you will most likely have to restrict the bypass somehow. A valve on the bypass allows you to balance the flow around the the engine against the flow through through the engine for optimal running temperature with a thermostat or no thermostat.

TRUE GRIT

The light bulb just went off for me! I had not completely grasped that a restriction was actually required when using a single stage thermostat. I will now prioritize installing a ball valve. Thanks, True Grit.

[Hymodyne]

thermostat use

Why have a thermostat in the coolant flow at all? When I told a marine engine mechanic, familiar with A4's that I had rebuilt an engine, the first question he asked was, " have you removed the thermostat?" I'm raw water cooled; is this need unique to FWC engines?

James

[hanleyclifford]

Why have a thermostat in the coolant flow at all? When I told a marine engine mechanic, familiar with A4's that I had rebuilt an engine, the first question he asked was, " have you removed the thermostat?" I'm raw water cooled; is this need unique to FWC engines?

James

Sounds like that mechanic has been to a few county fairs.

[BunnyPlanet169]

Take me to the fair.

The original design of the A4, with a double acting thermostat, made sense. As the engine warmed, the bypass closed by itself, and the primary flow opened in the head. Simple and elegant. Exhaust coolant flow stayed about the same as the engine reached temperature.

[FLAME_BAIT]
Personally, IMHO, I believe the single-acting thermostat with bypass is a kludge. It works, generally, for most people, but the idea of having to manually tweak bypass flow to balance engine cooling and yet still have enough water flow for exhaust during warm up is goofy. It's at best, a compromised attempt to replicate the original design. It's always the first thing we recommend disabling for cooling diagnosis, along with removing the thermostat.
[/FLAME_BAIT]

I'm going to run too cold this year without any thermostat. I know others do too. No bypass, no valve, no check valve, no fiddling. I have more water coming out of my exhaust than I've ever seen, and it makes me happy.

Next year, heat exchanger and FWC with an Indido thermostat.

[hanleyclifford]

Take me to the fair.

The original design of the A4, with a double acting thermostat, made sense. As the engine warmed, the bypass closed by itself, and the primary flow opened in the head. Simple and elegant. Exhaust coolant flow stayed about the same as the engine reached temperature.

[FLAME_BAIT]
Personally, IMHO, I believe the single-acting thermostat with bypass is a kludge. It works, generally, for most people, but the idea of having to manually tweak bypass flow to balance engine cooling and yet still have enough water flow for exhaust during warm up is goofy. It's at best, a compromised attempt to replicate the original design. It's always the first thing we recommend disabling for cooling diagnosis, along with removing the thermostat.
[/FLAME_BAIT]

I'm going to run too cold this year without any thermostat. I know others do too. No bypass, no valve, no check valve, no fiddling. I have more water coming out of my exhaust than I've ever seen, and it makes me happy.

Next year, heat exchanger and FWC with an Indido thermostat.

I think you've already been to a few, but take note that the double acting thermostat arrangement is only as good as the ability to seal in two directions. The vulnerability of the housing is well documented here and the Moyer organization must concur or they wouldn't offer the bronze replacement, a must for all such installations IMO. Thermostats on raw water engines are an exercise in ridicularity, again IMO.

[capnward]

my thermostat saga

My A-4 is freshwater cooled and the salt water here is around 55 degrees. I used to run without a thermostat, after the rebuild shop deliberately left it out in 2000. I was running at 140 to 150 degrees, and all was well.
Then I noticed reputable sources on this forum stating that the best temperature for a fresh water cooled A-4 is 180.
So I got a Honeywell thermostatic mixing valve that Indigo used to sell. It was a thermostat that you could adjust with a knob, and worked well for years. It melted internally, when the engine overheated because the fresh water pump seal blew out. I ran without a thermostat again, for a while, but wanted to run hotter. So I created a bypass between the manifold and the heat exchanger with two ball valves and a T-fitting. I could bypass the heat exchanger completely or make all the water go through it. After some fiddling I could get the engine to run around 160, but it took a while to get there. So I got the Indigo thermostat, which can be mounted away from the engine, and attached it to the heat exchanger. It opens at 160 and reaches that temperature quickly. I like it. See photo. (First time photo post)

I understand that Indigo also offers a 180 deg. thermostat, but my temperature alarm, which is supposed to close the circuit at 200 degrees, does it at 180. So I retain the 160 degree t-stat.
Twenty years ago I met Norman C. Blanchard of Blanchard Boat Co. the builders of my boat. He maintained and owned my boat from 1948 to 1977. (Her first engine was a Kermath.) He told me that too often people don't run their engines long enough to chase the water condensation out from inside the engine, and it leads to internal corrosion problems. If that is so, then a thermostat is a good thing, to get the temperature of the engine up quickly, as well as to reach higher temperatures which are said to be beneficial. I often just use the engine to get in and out of the marina, and I like to see the temperature reach 160 after just a few minutes. I would think a thermostat would be even more important in a raw water cooled boat in colder water.

[tenders]

I'm also (salt) raw water cooled and have run without a thermostat and with a blocked bypass since the early 1990s. The engine runs cool, as in about 120, no big deal. I just replaced the plugs after four or five years for no reason other than they looked a bit rusty on the top. No problems. Life is too short to worry about thermostats functioning in salt water environments.

[joe_db]

I too run the new Indigo thermostat. It warms the engine up very quickly and always maintains full flow. I have the 160 degree thermostat in mine for FWC. In 75 degree water running hard I get about 180 on the meter.
IMHO the OEM late model A4 thermostat is a kluge at best and expensive to replace on top of it.
The potential harm of running too cold is that water and acids in the oil never boil off. Without an oil temp gauge, we don't know for a fact that cold water = cold oil. Someone maybe should look into that. I know big diesels that don't get run hard suffer and some have special oil *heaters* to prevent issues. Here is an oil temp gauge with the desired operating range: