What temperature?

[tony201]

Mine stays at 70 at 1900 giving 5.9

[sastanley]

I'm still getting used to the cleaned out engine.

My raw water cooled used to run at around 180-190 with frequent spikes, back off the throttle and it would cool right down. Now it stays pretty solid at 155-165 except a MAJOR spike a week ago. I limped the last .5 mile of a 30 mile delivery (wow was that lucky!!) and when I went back to troubleshoot it was fine. I figure after all the cleaning I did last winter a piece of scale wedged somewhere unfortunate (manifold exit?) and settled again when it was shut down for a while. I'll continue to watch the gauge - and for steamy exhaust.

Uh Oh...good luck with the troubleshooting, dude!

[rigspelt]

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.

[Administrator]

Rigsy:

Don and I had a discussion about this a few years ago. His view was that the back pressure generated by the exhaust being underwater (at a depth within reason) was trivial. The engineer in me had to run the numbers. I forget exactly how the calculations came out, but as usual he was correct. In fact, some boats are designed this way.

Of course, if you're on the edge of a problem, I suppose you could see a performance effect, but my guess is that what you're seeing by moving the crew around has more to do with changing the hydrodynamics of the boat than back pressure.

Bill

[rigspelt]

Bill - thanks for that info. I doubt anything significant is going on, not after all the work last winter. Just settling in.

[hanleyclifford]

exhaust in the water

I must disagree with the notion that having exhaust partly under water does not affect performance. When I raised my transom exit 5" in response to this issue I got and immediate and noticable improvement in performance and economy.

[JOHN COOKSON]

Don't Always Believe What Temp You See On The Gauge!!!!

1. A4 was running at a temp of 180-190. (RWC)
2. Rebuilt the entire cooling system including new temp gauge and sending unit. Had excellent water flow out the back of the exhaust manifold.
3. A4 still running at a temp of180-190.
4. Rewired boat and engine.
5. A4 now running at a temp of 140-160. Seems to go through a normal warm up curve.

My theory: (Somebody please comment on this) Excess reisistance, I think it was in the ground circuit, was causing the gauge to read to read higher than the actual temp.

It is easy to check wiring with a jumper wire and an ohm meter. (This is how I found that the wiring had a problem)

Further proof would be to run with the jumper wire(s) in place and see if the gauge readings change.

[ndutton]

Just the Opposite!

1. A4 was running at a temp of 180-190. (RWC)
2. Rebuilt the entire cooling system including new temp gauge and sending unit. Had excellent water flow out the back of the exhaust manifold.
3. A4 still running at a temp of180-190.
4. Rewired boat and engine.
5. A4 now running at a temp of 140-160. Seems to go through a normal warm up curve.

My theory: (Somebody please comment on this) Excess resistance, I think it was in the ground circuit, was causing the gauge to read higher than the actual temp.

John,
Excess resistance would give you the opposite effect, reading lower than actual. The temperature gauge is little more than a voltmeter with the sender a variable resistor to ground. Zero resistance pegs the gauge at its maximum. The greater the resistance, the lower the gauge reading.

[hanleyclifford]

John,
Excess resistance would give you the opposite effect, reading lower than actual. The temperature gauge is little more than a voltmeter with the sender a variable resistor to ground. Zero resistance pegs the gauge at its maximum. The greater the resistance, the lower the gauge reading.

This is a solid reason why every owner should have a direct reading gauge to complement and verify his remote panel instruments.

[hanleyclifford]

Tom - All your numbers are right on target! I too am interested in entrance and exit temperature differential. I might add that it is worthwhile to monitor entrance temperature with a separate gauge (Or could a switchable gauge with multiple senders be developed? - hint, hint - Wish List) I have never liked the late model thermostat arrangement which is one of the reasons I put an early head on my late engine. Keep up the good work. Regards, Hanley

[edwardc]

I now have about 40 hrs on my Moyer-rebuilt short block, which I converted to fresh-water cooling using the Moyer kit. After starting, it quickly comes up to 180 deg and stays there over a wide range of rpms and load.

Last week, I spent 3 hrs at 2800 rpm motoring into an 18-20 kt headwind with 3-4 ft seas. Boat would labor up to 4.5 kts, then get slammed down to 2.5 kts by the next wave.

Temp stayed rock-steady at 180 the whole time.

With the boat in a slip, in neutral, at 750 rpm idle, it cools down to 165-170.

[Mo]

Raw water cooled.

I run with no thermostat; my bi-pass valve is opened to 45 degree angle; the temp never rides above 130 degrees.

If I have to do the valves on this engine every 3 or 4 years I could care less. I hold my fingers on the head or the block and it is cool enough not to have to haul my fingers away....like it or not...that's a good thing.

I have had an atomic four for 4 years. There are a couple of guys around here (my club) that have been using them for 30 years....it is beyond me that guys run these engines for that long and don't have a clue. They come to me to fix them. What bothers me is listening to the Horse...t they come up with because they heard it from some supposed guru....where was he when you burnt up you engine!!! Burn up an engine and it is done...bottom line.

Another bottom line...The head gets water, the block gets water and is gets a muriatic acid flush every 3 or 4 years. Not rocket science... and never will be.

Edit 1 "around here" meaning our yacht club.

[gary randall]

Way too cool

I have completed a rehab in which I removed the head, cleaned the passages the best I could and flushed it out.
The temperature gauge now reads a mere 115 degrees F., but the nut on the sensor near the thermostat housing is frozen and the connection seems a little glitchy.
So, I would like to get a secondary gauge to get the actual temperature. Where would be the best spot to attach the gauge? After reading Indigo's post about the variation in temperatures, I am wondering if there is a "sweet spot" on the engine that will give me a good optimum average.
Also, would an infrared thermometer work in this application?

[vabiker23518]

180 with FWC

MERLION had her engine overhauled by MMI maybe 8 years ago and FWC was added at that time. We bought the boat 4 years ago, and she seems to run at a rock steady 180...there is some exhaust steam when fully warm. I'd like it more around 160, but the temp will drop to 140 at idle within a few minutes, so I assume its spot on.

[hanleyclifford]

You have a good system if it will hold "rock steady" at 180 while at cruising rpm for any time period with FWC. But the fact that you drop to 140 at idle tells you that the thermostat is not really a "180" unless your bypass loop is so good at cooling that it can bring you down to 140 even with the thermostat closed.