Running without thermostat but bypass kit

[southcoasting]

I have been reading a lot of older post trying to understand the operating temp of our engine, bypass kit, different thermostats to use, etc

I have read about people running without a thermostat in place and just using the bypass kit sold here to regulate flow...

Out of curiosity, how many of you on here run their A4 this way? What has been your experience in doing so?

What can you say are advantages/disadvantages of running the engine this way?

[Marian Claire]

I half way qualify to answer. I run without a T-stat but I have a recirculating loop not a By-pass. The thing I like is I can adjust the valve and run at the temp that I am comfortable with. If I want 180, 140, 120 deg what ever. With the recirc loop you get 100% flow thru the block 100% of the time. The disadvantages are that you have to do the adjustment and therefor must have easy access to the valve. It is not like you are constantly adjusting but it is something to consider.
Just recently I had a issue with the raw water intake getting plugged. I noticed the temp rising so I closed the recirc loop and that bought me enough time to check the flow out the exhaust and realized what was happening. Dan S/V Marian Claire

[Dave Neptune]

southcoasting, I have run without the t'stat the entire time I have had this engine. It was siezed when I bought it and the t'stat was removed then! I try to keep my engine running under 130 only because I run for 5~6 hours early in the mornings with no wind on our way to the island and it keeps the cabin and settee bunk cooler for my wife daughter and the Giz to sleep comfortably as the A-4 purrs away below them.
If I ever do make any changes I will set it up like Dan with the recirculating loop to get some more temp. My lil' beastie still runs quite strong and has done so at 130 degrees for a long, long time now!! A good thing!!!
You will get a bit more life and performance at a bit higher temp, I just decided to make the temp trade off for comfort only!!!
If you can successfully regulate temp "MANUALLY" why bother using parts that are hardpressed to perform in a saltwater environment and need replacing more often than a differant type of valve???
If I ever go FWC I will use a t'stat, just one of a lower temp.

Dave Neptune

[Jesse Delanoy]

When I first was buying my A4 powered boat, the engine was running a bit hot according to the survey. The seller suggested he let his mechanic take care of it, and if he could get it mechanic certified to be operating properly, would I still buy the boat? I agreed, the mechanic went to work, and eventually certified that the engine was performing properly.

I bought the boat and had no problems with overheating the first year. The second year, I went to take out the thermostat, and was shocked to find that there wasn't one there! Didn't seem to hurt anything, however.

Couple of years later, after cleaning some gunk out of the water jacket, a different mechanic suggested I run it for a season with no thermostat, to help flush the residual gunk out of the engine. I did, and again, seemed to have no adverse effects.

As I learned more, I replaced the thermostat and tried different methods for keeping the temp down, with some success. Long term running without a thermostat probably is not a great thing if the engine runs too cool, but doesn't seem to bother things for short periods.

[southcoasting]

Thanks for the clarification guys!

I was wondering this since my engine ran a bit too hot...After looking around down there, I found out I had not installed the impeller clip properly, thus I wasn't getting enough cooling flow/pressure...

What made me think of this was when I noticed the head was getting really hot and when I took the hoses apart, it was bone dry...it's what prompted me to look at the pump/impeller anyways..

I after I fixed this, I topped off the antifreeze and ran the engine for about 20 minutes with it never reaching 180...

I had ordered the bypass kit and payed for the fast shipping anyways as I'm launching Friday and got in a panic...

I guess i'll install it later on after my launch as I don't want to fix what ain't broke...

[ArtJ]

Have you checked in the hoses and fittings (particularly where turns sharp
corners) for pieces of old impellers? Could even be from previous owners.
They will sometimes block flow and sometimes not. Worth checking out
even if you currently have a whole impeller.

Regards