Atomic 4 not reaching operating temperature

[Memphis]

My just overhauled Atomic 4 (1972?) is only reaching about 110 degrees on the test bench.
I ordered a new single action thermostat and the bypass valve, but I really don't see how that will help. The old double action t-stat tested okay, so I'll keep it as a spare.
During the overhaul I replaced the water pump with the newer more powerful version. Could that pump be over-powering the thermostat?
On the test bench my raw water is tap water at 55 degrees. Could that be the problem?
The engine is under no load on the bench, beyond driving the alternator.
Even at 3000 RPM, the head is hardly warm to the touch, and the only place too hot to touch is at the front of the exhaust manifold. I mention this as I naturally assumed my gauge or sender was bad.
I'm a rookie, so I'd love to get some cogent ideas about this problem (because I have no cogent ideas myself.)

[Mo]

Hi Memphis,

Welcome aboard. Typically, if there was a cooling problem you would notice it on a bench test. It does take a while for the engine to warm though. Some things that you need to check and ensure.
- have a water hose going into a bucket and the raw water intake hose takes water from that bucket. We don't plumb the water hose (under pressure) directly to the intake hose.
- I don't use a T-stat in my engine. I just keep the by-valve open about half. When operating like this my engine runs between 110 and 130 degrees and it will stay there even in rough weather when the engine is working. I put NGK XR4 spark plugs in mine and they run hotter ... this keeps the carbon in the combustion chamber minimal.
- I routinely pull the steps off my C&C 30 when running hard and lay my fingers on the head....if I can't hold them there (which never happened) I'd be worried...that is my insurance gauge. Never had one episode of overheating in the 6 years I've used my engine.

Typically, if my engine is running there is:
-no wind and heading out on the ocean to find some .. or
-rough seas and I have to motor in the direction I'm going typically against the wind and waves. (If my sails are down it`s blowing over 30 kts.)

There are basically four schools on cooling on here. All have pretty good knowledge of the engine and reasons why they like to set it up as they do.
-some like T-stat and run 160-180 on Raw Water Cooled
-some like no T-stat and use by-valve Raw Water Cooled
-some have FWC with T-stat
-some have FWC and no T-stat.

I could go on for hours and give examples of some of the boats that I`ve worked on and what we did to keep them from running too hot. The main consideration in my personal decision for my own was that I wanted to eliminate, as much as possible, an overheating issue when I needed the engine most...under load in a storm. My fuel consumption is in the ball park with everyone else so I can`t justify running at a higher temp.

Another thing I use is 15w40 diesel oil...been great, works great with reversing gear, keeps engine noise to a minimum. I rarely have to work on my own engine except to winterize and commission it....my knowledge and experience came from this forum and working on friends engines.

Hope that helps you out. Ultimately, you need to see where you want to be with it. I`m sure the guys will put their opinions here as well.

[ndutton]

Without load 110° is about right. There's a huge temperature difference between load and no load running and alternator loads don't really amount to much.

Even with load a raw water cooled engine doesn't heat up much. In water temps of 55° to 65° my engine would barely reach 140° with a thermostat and it took quite a while. That's good for a RWC engine because above 160° salt crystals start forming in places you don't want.