I have a Universal 5424. Even in 40 degrees, I just touch the starter button and it fires right up, as long as you give the glow plugs 40s. What you needed to do on the engine was fix whatever was wrong, not use starter fluid.Hey,
What happens if you try to start the engine 'as is'? Do you use the glow plugs at all? Does the engine eventually start? What temps are you trying to start the engine at?
My last boat had a Universal Diesel with about 4000 hours on it. It ran great but did not like to start when the temps were below 50. It had glow plugs, and I rewired them, and that helped, but the engine was hard to start below 50. I would have to crank it for over 10 seconds (when it was 70 out it would start in 2-3 seconds). If the batteries were low it would not want to start at all.
For me, the solution was starting fluid (ether). I know most people would not recommend it, but for me it worked great. Spray a 1 second shot into the intake, wait a minute, then the engine would start in 2-3 second when the exterior temp was 30. Since I'm mostly a fair weather sailor, I only used ether 3-4 times a year. I did that for 5-6 years without any problems.
Starter fluid is always a mask for whatever is truly wrong.