Operating Temp? Thermostat Kit Or Not?

[Sleeper CP]

Hey BP,
I have experienced a lot of what you wrote.
At the beginning of boating season when the water is cooler the water valve is closed down 1 - 1 1/4 turns more than in July-Sept(early) when the water is a few degree's warmer.
When my brother and I first got into boats 20 years ago I asked a lot of people about the water temp deal. I heard more off the wall answers and when I brought up the single pass/open water system I just got blank stares or "no the engine temp is the water temp". No it's not, not in a open loop system. That is when my brother and I decided to control the oil temp.
If the oil is hot, the engine is hot. If the oil is cold the engine is cold. Pretty simple. I still don't know if it's the best way to do it. I just know that I can control it and know what it is.
On the gauges: I don't like electronic sending units, that's all. And the 2 5/8 inch liquid filled guages look best.
As far as pressure goes: A 3/4" house regulator for $ 75.00 from HomeDepot will probably work or a $300. special marine one will do the job on the inlet side before the water enters the engine.
Sleeper CP
Big Inch Ford Lover

[bp]

i don't have any problems with elec gauges. in fact, just installed a whole new set, plus oil temp, in my brand new 30 year old 23' hallet supertanker jet. they work great, especially since i rewired the entire underdash.
oil lubricates and removes heat, so oil temp is critical. however, cylinder walls and heads aren't cooled by oil; heat is removed from those areas via water (and air). if you're keeping your water out temp at 140 or less at speed, you're probably ok with the oil cooler. but people that try to raise the water temp to 180 (because that's where there car temp is) stand a real good chance of having inadequate heat removal via those water passages and damaging the engine.
the thing about a regulator, zurn or the bypass duane sells, is that it must be able to provide 10-15psi out with fluctuating inlet pressures, which can get up there. wherever they come from, home depot, lowes etc., they have to function correctly all the time. i dismantle mine once a year and make sure everything is clean and spiffy.
i've seen pics of cooling systems with so many hoses running all over the place that you can't even see the engine, which is absurd and unnecessary. i've seen guys successfully run their cooling systems backwards (in at the top, out at the bottom of the block). i had one old friend (now deceased) that purchased a brand new 1974 witchcraft, 425 olds/jac. that engine's water temp never exceeded 120, running 500-600 lake hours per year for 25 years (he finally had it rebuilt in '99). the only problems he ever had were the occassional dead battery, and one time the voltage regulator went south.
for h20, keep it cool for best performance and longevity.