'91 Nautique closed loop cooling system - proper running temp?

[1StopJeff]

I am a first time Nautique owner. I purchased a '91 Nautique Excel with 444 hours with a closed cooling system. Even though I test drove the boat before purchasing and the temp was fine, the first time I took the boat out after getting it home, the temp shot up over 220 so I limped it home and pulled out the RWP and could tell that it had not been serviced in probably 10 years. (I was a boat mechanic some 25 years ago) I replaced the impeller and cleaned up the pump and took the boat out again and running at 5mph it runs at 200 degrees and running at 24 - 36mph it runs at 185 - 190 degrees. I have searched and read several threads and it looks like everyone is shooting for temps closer to 160 even though the PCM manual says that the normal operating temp for a closed loop cooling system is 180 - 200 degrees. The question is, am I missing something? Should I be trying to get this thing to run cooler?

[mrbobolina]

Ask the guys over at Whitelake Marine. They will know the exact closed lop running temp. If you are looking at your engine from the drivers seat. There will be a black square with 1 tube going down to the radiator (long cylinder) and I think one tube to the waterpump and another to the canister to the back of the motor. Anyway, in this square is your thermostat. i think it opens at 160 degrees. The entire system works like a car. Engine gets hot the steam opens the thermo and the water pump cycles it.

The impellor cycles the fresh water, the thermo and water pump cycle the cooling system which is literally coollant and water like a car. Do a google search on DIY for checking if a thermostat is opening. It is pretty simple.

Also look over all the tubes. It if they are stretched or cracked worth replacing. These are super reinforced tubing so they can handle alot, however the inners do break down. 10 years is along time and 444 hours if not taken care of is ripe.

Hope this helps.

[1StopJeff]

Thanks, yes I followed all the tubes and it all goes through a heat exchanger like a radiator and the engine cooling system has anti-freeze in it. I was just really looking for others with this same type of system to see if they are getting the same temps as I am. I plan on pulling the thermostat and possibly replacing it and am wondering if I should go to a lower temp thermostat.

[mrbobolina]

I have the closed loop system. I had a similar question/thought and read some place that doing so is not necessary. A closed loop system is really designed for keeping salt water out of the vital parts. A traditional non closed loop system is just taking lake water and pushing new cool water in all the time. A lower temp thermo is just overkill for the sake of it. At 444 hours I would look at things like your starter, spark plugs etc.

Th rule of thumb I was told as a kid was 100 hours on a boat is like 20k miles in a car. This is not a literal translation of course because as long as the boat is running the meter goes unlike car mileage right? It is a simple rule of thumb though. Soooo if you had bought a car close to 88k miles where you focus? Same rules.

If you boat has seen alot of trailer travel time look at your breaking system, fluid, etc. Take a closer look at any nuts/bolts that look corroded or hae buildup where grounds are. Either clean or replace them.

Mostly go relax and enjoy the time on the water.