What temperature?

[sastanley]

Brett,
What Neil said..My "backup" impeller is already installed on a new shaft, so it is a quick replacement, then I can deal with the other one not crammed down around the motor.

You need a pair of snap ring pliers. Moyer sells them here (pic below) or you can get them at most auto parts stores too.

Probably time for an acid flush if you haven't done one recently. If you want a less caustic approach, you can try a vinegar flush. This is a lot easier if you have a 3-way valve in your intake stream, but otherwise just plumb a hose from your water pump intake to a bucket..the water pump should suck out whatever recipe you mix in it.

Do you have a bypass valve installed between the side plate and the thermo housing? I found that helped stabilize my temps a little on my C-30 by forcing a little more water into the block...runs about 165 right now with no fluctuation at cruise speed..goes down to 145 or so at idle.

Oh..I just realized you are new around here...welcome! - let us know if our ramblings & questions don't make sense..sometimes we make assumptions..

[tartansailboat]

I just replaced my water pump, temp sender and gauge. A kindly forum member supplied a three spring Holley 140 deg tstat to me. Engine now climbs up to 145 deg rapidly, stays there rock steady just fine. I acid flush every two years or so but have never removed the two block drains to pressure flush the block but plenty of water out the exhaust. I had heard several years ago that with a RWC engine, you don't want to run much above 140 deg because of salt precipitation but Ken at MM parts indicates that 150 - 160 is OK providing you pressure and acid flush regularly. Personally I like a cooler running engine but have no good technical reason for that. Eleven years ago, the PO had removed the tstat completely with no valve in the bypass line, engine ran at much less than 140 deg, too cold for my liking.

[JOHN COOKSON]

Reserve Cooling Capacity

Personally I like a cooler running engine but have no good technical reason for that.

I have a very good reason.
If you're running ~140 and a piece of crud suddenly blocks the water intake and the temp shoots up to ~190 you can still carry on - at least for a while at reduced speed.
If you're already running at ~190 and this happens you'er dead meat. Or dead in the water.

TRUE GRIT

[Mo]

Hi John,

Mine runs cool and ...RWC no T-stat and by valve open about 1/2. This engine has not overheated in 5 years that the boat has been mine. Acid flush every second year. NGK XR4 plugs keep combustion chamber clean, no valve problems since fixing initial problems that came with the boat.

Have seen two cases of overheating with FWC systems this season alone. Both were fairly new systems and both had T-stat failure. They run around 180 degrees on a good day. I like like the idea of having some room come up.

I mentioned that they should talk to some of the guys on here with FWC that run with no T-stat. Didn't know enough about it to offer an informed opinion.

[keithems]

maurice--

as u know like u i have a c&c 30

mine runs very cool, but i'm really not concerned.

it seems happy if u know what i mean...smooth, warm to the touch...more important..oil is warm

i wonder if ours run cool because they are not encased the way they are on other boats? i know from flying that if u open the cowl flap just a tad, the cyl head temp can easily go down by 20-30 degrees.

on my boat, i've removed most of the engine sheathing -- i think good access is paramount...plus, i wonder if my running in fresh lake water means again running 20 degrees cooler, since fresh water is a better cooling medium than salt.

finally, i run 10w40, a much thinner oil, which again should mean a cooler temp.

btw-- i use the dave neptune cooling mod..pretty much like you -- no t stat, manual bypass valve and also one where the cooling water exits the manifold...usually they're both open.

also, my block and head were hot tanked recently, and i was told the cooling passages are nice and clear. was also told my manifold didn't need it.

[Mo]

That hot tank info is nice to know for sure. I still do an acid flush every two years and I think it does wonders to reduce buildup internally. Nice clean ports help for cooling. I have the side bulkheads on, however, I cut and made them hatches for engine access so it take a minute to remove.

I hardly have to touch my engine...seem to have my head in over someone else's all the time. Yesterday helped a friend with his oil pressure adjustment...fixed that and went to check my own. It was corroded so I cleaned up the threads. Other than checking oil, changing oil and turning the grease cap on the water pump, that's the first thing I did with the engine this summer.

Keeping them cool is the trick. Enjoy your boat and your summer

[Dave Neptune]

New way maybe

Kiethems and Mo, I have just made a few modifications to my t'statless A-4 that have worked quite well for better temp regulation via the bypass. It works far better, runs warmer, less temp rise after shutting down and I've now run like this for around 18 hours over 3 trips to the island. I will be posting my set up soon on a separate thread and don't want to hi-jack this one further.
If either of you are interested try a PM and I'll elaborate a bit. Should have the instalation tidied up for a pic and post in a few days.

Dave Neptune

[gfatula]

Why is there a different "preferred" operating temp for fw and rw cooled engines? The engine shouldn't care! My raw water is around 50 degrees f. I have a fw cooled engine. I am thinking someone in VA is cooling their fw cooled engine's coolant with rw closer to 80 degrees f. It is going to make a difference for fw cooled engine operating temps in both locations. No?

[ndutton]

For RWC engines, beyond about 160°F salt begins to leach out of solution clogging the cooling passages. I've seen manufactured RWC mixing elbows (exhaust) completely closed off with salt. The engine prefers a higher operating temperature like 180 - 190° but in the case of RWC the cooling medium can't tolerate it.

[sastanley]

gfatula,
I am in the Chesapeake and the tributaires of the Bay normally get into the high 80's..the highest I remember seeing this year on my ST40 depth/speed/temp instrument was 88.9°F at about 18 inches down.

I think there is no simple answer to your questions. I can explain my personal scenario...

RWC - clean waterjacket I was running about 150°F at idle & 160°F the rest of the time...
As the deposits in the water jacket increased, I was seeing 170°F or so, and more fluctuation in the readings (t-stat more active)..
In the winter, I was not usually able to get it that hot...
When I first had the boat (December 2008 haulout, estimate water temp around 45-50°F) I could not get it over 120°F. But the engine was also very anemic and not producing a whole lot of power either.

Fast forward to FWC - I am using the Johnson CM-30 electric pump for the antifreeze..so, it pumps at the same speed no matter the engine RPM. I've also noticed now that the raw water pump has less restriction and is only going thru the heat exchanger (i.e. no t-stat/block/manifold), even at low RPMs I have a LOT more raw water coming thru the exhaust. The limitation of the raw water pump and the restrictions it was seeing with RWC I think is no longer the engine, but I think finally the 3/8" NPT inlet & outlet on top of the water pump itself. Everything is 5/8" hose and cast fittings & pipe nipples...no machined (restrictive) 90° fittings & no hose barbs anywhere.

idle-1,000 RPM 140-145°F
1,500 RPM 155°F
2,000 RPM+ 180°F w/ sea water temps below 80°F
2,000 RPM+ 190-195°F w/ sea water temps above 80°F
I also have a small-ish two-pass 2" diameter HX (Sendure 2AT-15 to be exact). I'd like a 3" multi-pass HX for the summer time when the Bay is close to 90°F and my engine temps are pushing close to 200°F...I think I am on the ragged edge of HX capacity at 2,000 RPM. - If I throttle back, the nice thing is the electric pump still moves the antifreeze at high capacity & my engine temps drop back to about 180°F pretty quick.

I am also still running the single action t-stat in my engine..I also noticed that the 'bypass valve' gives me a few degrees colder on the gauge with FWC, but not the dramatic difference of 5-10° it made with RWC, between open & closed. T-stat will probably come out this winter, and we'll see if that helps with my 195°F readings in the middle of summer.

So, since I have a small HX, I think that maximizing flow thru the HX on the raw water side and having constant flow on the fresh water side is the ticket for me..I need to get my IR thermometer back from my neighbor, because I'd like to measure the temps of the two sides at various places within the system for even more data points and quantify some theories. There has also been discussion around here that things flowing too quickly in the HX can make it run hotter because there is not enough time for heat transfer (& things like a three or four pass HX will transfer heat better than a one or two pass, which I think Neil has been able to prove sufficiently already with his HX tests). Anyway, the IR thermometer will help me with that.

[gfatula]

Thanks guys,

It was this forum that convinced me to add fw cooling to my purchase of an exchange rebuilt from Don. Glad I did. I would be adding it now if I hadn't then.

Thanks again and again. Ha! Good stuff! All of it!

G

[ernst]

Carefully adjusted to 180deg, with the Indigo Freshwater cooling thermostat (or whatever the thing is called). Stable like a rock.

[toddster]

Since acid-flushing the block and adding a hot water heater into the FWC loop, mine has been rock steady at 150F. Raw water temperatures have been around 65 - 70F. Stock thermostat, small sendure hx.

[Van_Isle]

Still getting used to this FWC A4. Yesterday noticed while at cruising speed for first time that temp was 175 but dropped to 165 when I sent crew forward to bring exhaust outlet up clear of the water surface. It is well clear at lower speeds and sailing. Boat squats and acquires a stern wave when running at full cruising speed, so need to shift weight forward or drop RPMs a bit. Example of backpressure, maybe? Lowering RPM does not sacrifice too much speed.

Turns out lower stern is typical for C&C 27 fitted with wheel pedestal and A4. Helps to switch from the Mark I/II scimitar rudder to the lighter/longer Mark III rudder, and maybe from wheel to tiller. Hmm.

My 79 C&C27 MkIII with wheel steering (and of course MkIII rudder) squats. Project in the works to move the batteries forward to under the aft dinette seat should shift a bit of weight forward. I assume your water tank is in the forepeak? I try to keep mine topped up even if we are just daysailing.

My rebuilt FWC A4 (years ago) runs at 140 to 150 ... I don't think I have the correct thermostat in it ... it was the one running in the engine when it was RWC. After determining that the themostat that was initially put in during the rebuild wasn't opening (I was pushing 200) the only one we had available was the old one.

[Mo]

My 79 C&C27 MkIII with wheel steering (and of course MkIII rudder) squats. Project in the works to move the batteries forward to under the aft dinette seat should shift a bit of weight forward. I assume your water tank is in the forepeak? I try to keep mine topped up even if we are just daysailing.

My rebuilt FWC A4 (years ago) runs at 140 to 150 ... I don't think I have the correct thermostat in it ... it was the one running in the engine when it was RWC. After determining that the themostat that was initially put in during the rebuild wasn't opening (I was pushing 200) the only one we had available was the old one.

Running 140-150 .... that's not bad. I wouldn't be sweating that.