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.
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.
...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.
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"
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?
Cap'n Tom
Live NOW or die a SLOW death; Live your dreams, don't dream your life.
[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.
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?
Last edited by sastanley; 08-25-2009, 03:07 PM.
Reason: update
-Shawn "Holiday" - '89 Alura 35 #109 "Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!)
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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?
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.
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