Too cold

[Skywalker]

Motored around yesterday looking for my mooring. Pushed her for a good 30-40 min.

The engine never warmed past 120 degrees.

I have an early model, fresh water cooled. The PO installed a new Moyer heat exchanger.

If you recall, I previously owned the boat. The old heat exchanger was half the size. A receipt from the marina the PO used notes "overheating, heat exchanger not sufficient, replaced". Now, I ran the boat for years with the old exchanger at a nice 180 degrees. I figured the marina just wanted to rip off the PO, like they did several times.

I'm embarrassed to say this, but I'm not 100% certain my old A4 has a t stat. I don't think it does. It was optional I think on early engines. I'll find out this afternoon after work.

I'm thinking there was an overheating problem, the yard took an easy route and changed what looked to be a too small exchanger (it only worked for 20+ years)

Now, without a t stat, the new exchanger is too efficient.

I guess I could install the t stat MMI sellls. I was also thinking I could restrict the flow of the water, but which one, fresh or raw?

I was thinking of experimenting by closing down the intake valve a little and see if the temp climbs.

What do you think?

Chris

[Mo]

Chris.
I'm raw water cooled and hang in the same temp area as you. To keep from having carbon buildup on plugs and top end I run plugs NGK XR4. I also find that prolonged run time on the engine brings the temp up to 140...I am talking running through waves and swells at 5 kts (1/2 throttle) as I have to do sometimes heading down the shore for a weekend.

I understand that some protected areas won't be hit by wave after wave trying to stop the boat and the engine doesn't have to be throttled up much at all to maintain 5 kts. When I am out there in punching through waves though I really like the engine staying cool.

Our typical summer wind is SW and 20-25 kts sea breaze is not uncommon. Typically pick your day and have that on a broad reach to your destination and back. When the wind lays down, allot of people then want to go. Determinant factors are kids aboard, seasick tendencies etc....but thinking the sea is settled. The wind may die down but the sea can take 24 or more hours after the wind dies to settle.

Once these wayfarers get out around the head of land onto the Atlantic they find they have to motor sail to keep the boat moving as swells waves affect the ability to move in what little wind there. Typically they start out sailing then motor sailing and maybe onto the engine alone at some point.

Overheating issues are not just an issue with the A4. Today here the wind is SW and going to go to 20-25. Quiet right now and people are having a leisurely sail out the harbour...they will round the head and get into yesterdays swell and put up with that for a bit. Then they will motor sail for a bit. The wind will pipe up around 1pm and then some will drop the sails and motor ... others will sail it down the shore.

People will go for the engine today (both diesel and gas powered) and some will overheat for various reasons. THAT is a typical Saturday here and they get a damper put on the weekend and spend a week fixing the boat.

And that is why I like to run cooler...

[Skywalker]

Wow. Interesting conditions. Sailors around here run for shelter at 20 kts! Wimps. That's when I love how my little Tartan sails.

Here on Long Island Sound, July and August bring us 5-10 kts most days, lucky days are 10-15! Not much of a sea state, as you can image. Water temp yesterday around 70 in the harbor. The boat glided along, 1300 rpm, didn't have my knot meter or gps hooked up yet (they are now), but I'm guessing 5 kts of boat speed, maybe a little more.

Sounds like cooler is better (safer), but when does carbon build up become a factor?

Should I consider a restricting valve in the coolant line?

Chris

[Marian Claire]

Skywalker. I have an early FWC A-4 with the MMI HX and no T-stat. I have gone thru a few set ups to control operating temp. Resticting the RW flow out of the HX is better than restricting the RW flow in. I was told that the pumps can deal with head pressure better than low flow. I have a recirculating loop that allows some warm FW to flow back to the FW pump and mix with the cool FW from the HX. A valve controls the amount. The biggest issue is that you have to have good access to the control valve. But it is not like you have to constantly adjust it. I will try to find a post that discribes my system or just search using Marian Claire and recirculating and it should come up. Dan S/V Marian Claire

[Skywalker]

Dan

Thanks. There is a loop in mine system after the housing too. I'll go to the plumbing supply and get some parts. Luckily my access is good.

[romantic comedy]

I have FWC with a huge heat exchanger. It was on a large V8 engine, and I adapted it.

My engine runs at 180 all the time. It may cool down a bit when at low RPM. I have the original thermostat installed. The by pass has a valve that have used maybe 3 times, when it went to 190. ( I probably did not need it)

Point is:

I have a huge heat ex, and t stat. Runs at 180. tartan 34, 12000 pounds, indigo prop, 2000 rpm cruise.

[Marian Claire]

" after the housing" Are you refering to the Dole T -stat housing on the manifold exit? Or do you have a late head? I used the old and empty Dole housing for the T. There is a album on my profile that shows my set up. Please note that the squeeze bulb shown has been removed. Dan S/V Marian Claire

[Loki9]

I run my FWC A4 with the thermostat kit from Indigo http://atomic4.com/thermostat.htm

Cruises rock steady at 180F, no regrets.

[Skywalker]

We are preparing or our 8 day trip to Columbus for the US fencing championships, but I made it to the boat today. This is what I learned.

I do in fact have a thermostat. That early housing doesn't look like much, but I pulled it apart. I brought the t stat home, put in in a pot. It opened around 150 (dont know how accurate the thermometer is, but close enough to the advertised 140 I guess).

The flow is troubling me. The coolant leaves the block and enters the housing, the closed t stat forces the coolant right toward the heat exchange from an opening in the aft end of the housing. The t stat, when open, allows the coolant to flow around a loop from the fore end of the housing that Ts back into the primary line back to the heat exchanger.

I don't get it. I don't see how this allows the engine to warm up. Obviously, it isn't!

The sending unit is on top of the housing.

I'll try to post some pictures.

Chris.

[Skywalker]

here are some picutres

first the housing



the t stat in the housing



how the loop is fomed



exploded view of parts in loop.



hope this helps

Chris

[Skywalker]

Btw, yes, I am going to cleanup the rust and paint! This was under the loop, and I didn't see it!

[Loki9]

I'm not clear on how your system is plumbed, but try looking at the diagram on page 9 of this document it might help.

[Skywalker]

Thanks jeff. That makes sense. What I have doesn't.

I've gotta do some more diagnostics!

Chris

[Marian Claire]

Sounds like if the line from the aft end of the T-stat housing was T' ed into the line from the HX to the FW pump the system should warm up. Basically you would be bypassing the HX until temps built up and the T-stat opened. Dan S/V Marian Claire

[Skywalker]

Dan,

That's what I was thinking, just like the diagram.

Why I have this circular loop around the t stat but into the same line to the hx is beyond me.

Time to buy some hose and fittings.

I'm also thinking about a valve in the line that goes to the T in between the hx and fw pump to control the bypass of the hx.

Chris