Keel cooling

[FAST FRED]

Thermostats don't work so fast it would cause such problems.

Come to Florida , you can have a ride on our 6-71 powered 50 ft US Navy Utility , converted to a cruiser.

The engine runs 180F (two new thermostats) and when the pair open the water drips to 160 , and in 4 or 5 min its back to 180.

We are in Florida , the water temp is usually over 60F , the keel cooler is 2 lengths of 1 1/2 water pipe 21 ft long .

Yes over cooling IS a problem. And a bypass thermostat is one solution.

FF

[TeddyDiver]

Maybe 20F lower temp for few minutes is problem for you but that's nothing.. Drill a bit bigger hole on the thermostate plates (hole that allows a bit circ to cooler when the thermostate is closed).. problem solved.
BR Teddy

[Submarine Tom]

OR... tandem your thermostats for higher flow rate...

You may want to try staggering the opening temps: one higher than the other, I don't know...

-Tom

[sbmar.com]

No formulas, just past experience on a typical 15 K's boat with a 300 HP diesel-- 40 ft of 2" galvanized pipe has no issues keeping the engine right at the 180 F thermostat level in 60F water under varied operating conditions.... Never used the vessel as a tug or push boat (WOT with zero head way), but that's a different set set of calcs.. Maybe 50-100% more pipe??


Tony

[singleprop]

I used John Deere Document AG-24 to calculate the length. I think it is quite conservative (no extra padding needed) and I came up with a total of 150 feet of 3.5" half pipes divided into 3 pipes of 25 feet on each side of the keel..for a 160 HP engine!

It seem a lot but if JD are using these numbers then I can too......

The document is quite specific with input data such as pump flow, heat rejection numbers (BTU/MIN), number of half pipes, boat speed, pipe size.

If anyone has the document can they help me confirm that my calculations are correct, based on a 160 HP engine, 5100 BTU/min, 6 kts and 3 parallel paths???

I think that I will arrange each run with a manual shut-off valve so that I can finetune the flow to keep the keel cooler return temperature around 20 degree lower.