A4 thermostat

[CowboyPhD]

Does anyone have a part number or make for a late model engine thermostat? I'm taking family out on tues. afternoon and am in need of one. Auto Zone and O'reilly's are open Tues morning.
Thanks!!

[cardiacpaul]

you might try here...

http://www.marinepartssource.com/uni...atomic4fmp.asp

drill down for alternatives

[CowboyPhD]

Yeah, I've seen all that. It's just that it's an eight dollar thermostat, and I was trying to buy it from someone who doesn't put the word marine in front of it and charge double. Turns out it's a "performance truck" part readily available for eight bucks on line.
Thanks for your time though!
Chers,
GCC.

[capn_dave]

Tr bad news is the A-4 doesn't use an $8 thermostat. The thermostat is what is called a bypass type. When it is closed it allows water to be circulated through the head only. As the engine warms up the thermostat opens and directs water through the block.
The correct thermostat costs about $80 and is available through Moyer Marine.
There is word that a thermostat from a Volvo engine will fit. Most people do a little plumbing and install a valve between the thermostat housing and the side plate water inlet. That way you can control the temperature manually.

Fair Winds

Cap'n Dave

[CowboyPhD]

Yeah, I got the Volvo one online. 12 bucks shipped.
What happens if I run without a thermostat?

[capn_dave]

Sorry I haven't replied sooner, I am in Georgetown Bahamas right now and not always on the boat.

If you use the Volvo thermostat place a 1/8 inch spacer, in the shape of a gasket on top of the thermostat.

Believe it or not a weird thing that is not like a car is when you remove the thermostat in the A-4 it will still overheat. That is because it is a bypass type. What you have to do is pinch the bypass hose partly closed. Mess with it a little with regards as to how much to close off by engine temp. The bypass hose is the hose that runs to the side of the block with the T in it that comes from the raw water pump. With the hose not blocked most of the cooling water runs through the head and very little gos to the block. You are trying to balance these two.
I am going out to dinner now with some friends and will be back in the morning.

Fair Winds
Cap'n Dave

[tenders]

Lots of people feel otherwise but in my view the penalty for overheating your engine (risk of warped head, seized engine, or fire) is much worse than the penalty for underheating (slightly fouled plugs--which in my case has not diminished engine performance at all).

Ten years ago I removed my thermostat and placed a short 1/4" stainless bolt in the bypass hose next to where it attaches to the thermostat housing. This forces the vast majority of cooling (raw) water through the block.

My engine runs at about 115-120 degrees by the temperature gauge, there is one less thing to troubleshoot if something goes wrong, and I have 100 degrees of safety in case an impeller fails or a plastic bag gets sucked into the cooling intake.

Forcing the water through the block also makes the engine much easier to winterize. I don't think there is a reliable way of doing this with the thermostat in place, and it is a pain in the neck to take out just for the 45 seconds it takes to run antifreeze through it.

I would probably feel differently about the absent thermostat if I had freshwater cooling installed.

[cspacek]

my 1974 atomic-4 gas engine has several petcocks on the sides of the block for draining raw water from the block for winterization.

[jjtjr]

Running an a4 without a t-stat is not good. The engine will run too cold and cause the valves to stick due to a carbon build up behind the valves,
on the stems. The engine should run at about 140 deg. This info came from Metalest marine thats the company that built the engine. Many years ago when I first purchased my boat I had that problem when I called the company up the service dept. said that I most likely did not have a t-stat in and I had stickly valves. Well he was right! I installed a new t-stat and ran mistery oil in the gas until the valves cleared that was in 1980 no problems since then. s/v cinnamon irwin 32.5 cc ketch
jake in nj