What temperature?

[Administrator]

At Jonathan Welch's suggestion, here's an opportunity to participate in a poll regarding your engine's temperature when fully warmed up.

Bill

[Jesse Delanoy]

When I bought my '77 Catalina 30, with original RWC A4, 9 years ago, it ran pretty consistently around 180 warmed up, under load. Not so hot as to be problematic, but hotter than I would like. I tried everything I could think of. Pressure flushes. Acid flush. Opened up the side plate and cleaned out the gunk. Put a restriction on the bypass. One season, on advice of a local mechanic, I blocked off the bypass entirely. Replaced the thermostat. All with no results.

Three seasons ago, the old girl finally gave up the ghost, and I installed a Moyer rebuilt replacement engine. I thought, finally, I'll be operating at the desired temperature. No such luck. Still running right around 180.

Along with many other projects along the way, I undertook to replace the three mismatched gauges on my instrument cluster. The gauges (and associated sending units) of course did not get replaced with the engine - my mechanic simply installed the old ones on the new engine. The oil pressure gauge and ammeter went in quite easily, but I COULD NOT GET the old temperature sending unit out of the cylinder head. It was stuck in, absolutely fast. I tried with every vise grip I could get my hands on, and succeeded only in wearing the hex-head on the sending unit down to a near perfect circle. I gave up on it for about a year and a half, and just lived with the old gauge.

This spring, during re-commissioning, I was thinking about having the old sending unit drilled out - not sure if this was possible since there's only about 3 inches of space between the front of the engine and the front of the engine compartment (access is from the top down). But I had the engine warmed up during an acid flush, and wondered if I could get the sender out while everything was nice and hot. I put a vise grip on it as tight as I could possibly muster, and whacked it about three times with a rubber mallet, and sonofagun if it didn't loosen right up. I was thrilled.

Anyway, to make a long story short (I know ... too late!), I put in the new sending unit and temperature gauge I'd been sitting on for a year and a half, and guess what? Engine is now running consistently at 160 - 165 under load.

I'm guessing there was a long-standing mismatch of temperature gauge and sending unit - the original SW gauge had been replaced with a cheapo at some point prior, and I bet the sending unit had never been touched. These two items must be matched up, or the gauge readings are suspect. I spent eight years worrying about an engine that probably was never overheating.

[roadnsky]

160º at 1700rpm in calm water at 5.5k. (Oil at 40psi)

[Mark S]

I answered the poll "160 degrees" based on what our gauge read last year when it was operating. I still haven't got it working this spring. I think the engine is operating a little cooler now than last year, based on what it feels like when I touch it, because of some off-season improvements and maintenance: (1) I cleaned the thermostat which was really ugly; (2) I installed the by-pass valve which I close when I think the engine ought to be warmed up; and (3) I gave it two vinegar flushes. Of course it could simply be a five to ten degree difference in May and September ocean temperatures.

Mark S

[rigspelt]

Originally Posted by Jesse Delanoy

...wondered if I could get the sender out while everything was nice and hot. I put a vise grip on it as tight as I could possibly muster, and whacked it about three times with a rubber mallet, and sonofagun if it didn't loosen right up. I was thrilled.

That really is one sweet feeling of relief. Happened the other night with a throughull that finally turned out.

[Dave Neptune]

I have been using a valve in the bypass line for 26 years now on a raw water cooled application. Yes I do run a bit cold (130 degrees) however I run easy until the temp has come up, after that I run at 2000 RPM's with the Indigo 3-blade.
One thing I do check is when I turn off the A-4 after a long run I switch the ignition back on after about 4-5 minutes and she reads about 140~150 degrees which is approximately what the core of the engine is actually running at. I think the water bypassing the block cools the "thermostat corner of the head" just a bit affecting the reading on the gage when not using a thermostat.

Dave Neptune
1970 E-35MkII original A-4 still "ticking"

[Capn Tom]

I've got one for "me hardys"! A previous owner (#1 or #2) removed the thermostat. He ran a hose from the t-fitting that's supposed to run to the t-stat and instead ran it to the manifold. The hose also has an on-off valve in it. I assume he had overheating problems and thought this was a solution? I don't use the hose in the on position.
My engine used to run up to 160; sometimes a little higher until I acid flushed. It then started running at 110. I always flush the engine with fresh water after using it (it is raw water cooled) to get rid of any salt.
Sidenote: Last week I replaced the riser because corrosion ate right through it.
Should I leave it alone or put back in a t-stat?

[MikeB.330]

between 170 and 180 just like a freshy should.

[67c&ccorv]

[QUOTE=Jesse Delanoy;14474]The oil pressure gauge and ammeter went in quite easily, but I COULD NOT GET the old temperature sending unit out of the cylinder head. It was stuck in, absolutely fast. I tried with every vise grip I could get my hands on, and succeeded only in wearing the hex-head on the sending unit down to a near perfect circle. I gave up on it for about a year and a half, and just lived with the old gauge.

"Firstly, vice grips are not for removing nuts or bolts - they are a last ditch attempt when a proper fitting wrench or socket is not at hand and you absolutely must remove the bolt/nut. Try gently heating the area around the bolt or thread with a propane torch and then put some effort on a proper fitting wrench."

This spring, during re-commissioning, I was thinking about having the old sending unit drilled out - not sure if this was possible since there's only about 3 inches of space between the front of the engine and the front of the engine compartment (access is from the top down). But I had the engine warmed up during an acid flush, and wondered if I could get the sender out while everything was nice and hot. I put a vise grip on it as tight as I could possibly muster, and whacked it about three times with a rubber mallet, and sonofagun if it didn't loosen right up. I was thrilled...I'm guessing there was a long-standing mismatch of temperature gauge and sending unit - the original SW gauge had been replaced with a cheapo at some point prior, and I bet the sending unit had never been touched. These two items must be matched up, or the gauge readings are suspect. I spent eight years worrying about an engine that probably was never overheating.

"Yes, gauges and their senders must be matched or the readings will be innacurate!"

1967 early model Atomic 4 with Dole thermostat runs steady 140 degrees on Great Lakes freshwater after warmup on my C&C Corvette.

[sastanley]

Hi Bill,

Great idea..I also like roadnsky's additional details for his particular situation provided.

Here's mine: 160-165 at 1,500 RPM. For now that's my 'favorite cruising speed'. The speedo says 4.6 knots , but it is new and not calibrated.

What about a similar poll for typical oil pressure? I dunno how well that would work since that reading probably fluctuates moreso than temp, but I would assume most have a 'standard range' they see at their favorite cruising speed which could be detailed in a topic reply after the poll entry.

Edit - update time.

So, now that I have been using the boat a little more I have been experimenting with the bypass lever.

With it wide open, I am closer to that 165 F & it fluctuates a bit...it'll go above 170F and then down to 160. When I close the bypass all the way, it is much more stable at 155-160F, but I also notice not as much exhaust flows out of the pipe either. I would assume this is because until the thermostat opens, only the small amount of water sneaking thru the closed t-stat is making its way to the exhaust. Is there any other place water can get to the manifold besides thru the t-stat bypass or the t-stat itself?

[Administrator]

Got it, Shawn!

Bill

[bcooke]

My understanding is that raw water cooling is usually around 180 and freshwater cooling is around 160.

Does that sound about right?

My freshwater cooled A4 runs right at 160 no matter what sort of load its under.

[MikeB.330]

bcooke, you have that backwards. 160 for sea water cooled and 180 for fresh water cooled is what you're looking for. Your's is a bit cool for a fresh water cooled engine. Are you sure you have the correct Tstat instaled?

[alberg]

At operating RPM's of 1550 my temp is 145 deg on my VDO matched 4 gauge unit. However after running and then idleing it drops to 100 deg.

Alberg

[ne57301]

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.

[tony201]

Mine stays at 70 at 1900 giving 5.9

[sastanley]

Originally Posted by ne57301

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]

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]

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]

Originally Posted by JOHN COOKSON

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]

Originally Posted by ndutton

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