Fisher Panda overheating

[zippy]

I have a 2014 Fisher Panda 12 mini with 900 hours on it. I am getting a cylinder head overheating temperature warning. The boat is new to me but the generator ran fine for a few weeks. I have changed the impeller and checked raw water intake as a first step and been trying to determine my next step by observing the temp read outs. Ambient temperature is 86. When the head temp reaches 220 first alarm sounds. Exhaust manifold is only at 96, fresh water is 89 in/96 out, raw water is 86 in/89 out. Running the generator again while still warm, fresh water 111 in/116 out; raw water 86 in/89 out. Should raw water out be higher? If so, I expect heat exchanger needs cleaning, but why is fresh water out remain so low? I can’t observe raw water out as it is below the waterline. Could someone provide the normal temps for the raw water in/out or provide suggestions as to what the problem may be. Thanks

[rbk]

I would also pull the heat exchanger then work from there.

[svHyLyte]

Zippy--

From your description/temps, it is likely that you have excessive scale build-up in the heat exchanger. You can use a product such as Barnacle Buster to clean the tubes in place by disconnecting the raw water input line and the tube to the mixing nozzle on the exhaust manifold and recirculating the Barnacle Buster solution through the circuit by putting the solution in a bucket and immersing a small submersible bilge pump in the solution with its discharge line connected to the raw water input side of the circuit and a hose temporally connected to the discharge side of the circuit and led back to the bucket. (Put the pump in a length of a nylon stocking to act as a debris filter.)

Start the process with fresh water only from a garden hose, counter flowing it into the discharge side and out the input side of the circuit to remove sediment build-up. When that runs "clear", mix up your solution and recirculate that as described above for 2-3 hours.

The fresh water side of the circuit can be cleaned in the same manner with a fresh Barnacle Buster solution by using the discharge side of the engine's fresh water/coolant pump and the return line from the heat exchanger led to the bucket of solution. Again, circulate the solution for 2-3 hours.

I have used the foregoing method on our Panda with good results for many years. It has now become a semi-annual maintenance routine.


FWIW...

[zippy]

Thanks for the detailed procedure, i will do this next.

[svHyLyte]

Zippy--

The pump I use, purchased many years ago, is a Rule 800. I power the pump with a small Duracell AGM 12 volt battery from Batteries Plus. It's about a 12 AH battery and so has no difficulty powering the pump for several hours or more. You may be surprised by the amount of sediment that you'll blow out of your system with the fresh water flush (both raw water and coolant/fresh water side). Once you've run the Barnacle Buster or Rydlyme solution through the circuits, a subsequent fresh water flush will discharge even more debris (you'll likely be surprised as was I the first time).

On the coolant/fresh water side, once you've done the final fresh water flush you can use a shop vac to suction out the residual water in the circuit, working from the discharge side and then the input side so that there is no unexpected dillution of the coolant when you recharge the circuit. When you do so, you'll need to "bleed" the air out of the circuit by opening the small vent atop the heat exchanger and powering the coolant pump with your 12v battery, above, Once you've gone through the process I have found it easiest the "top off" the coolant level in the heat exchanger by removing the vent screw entirely (don't drop it or the seal!) and introducing more coolant drawn up with a small epoxy syringe (West Marine)--cut the tip off a little--until the tank over-flows slightly and then re-inserting the vent screw. Bleeding the system as described is very important or you will suffer overheating yet again and the method described seems to work best/fastest.

FWIW...

[zippy]

Access to the generator is quite restricted. Do you access the raw water input immediately below the impeller pump; and the raw water output on the side of the box where it goes to the vented loop?

[svHyLyte]

Originally Posted by zippy

Access to the generator is quite restricted. Do you access the raw water input immediately below the impeller pump; and the raw water output on the side of the box where it goes to the vented loop?

"Restricted Access" is the bane of generator installations, frequently leading to poor maintenance. N'any case, one would access the raw water line to the heat exchanger on the discharge side of the pump, between the pump and the vented loop, on one end of the raw water circuit and between the heat exchanger and the injection nozzle on the exhaust manifold on the other.

FWIW...

[zippy]

I found my my generator problem. There is a hole in the “stainless “ fresh water pipe leading from the heat exchanger output. I am checking on getting a new pipe, but I think the original could probably be repaired.

[a64pilot]

Just looking at it, is it possible the whole thing could be replaced with a hose?

[zippy]

There is no coolant filler cap on the generator. Is the coolant supposed to be filled through the expansion tank?

[a64pilot]

Originally Posted by zippy

There is no coolant filler cap on the generator. Is the coolant supposed to be filled through the expansion tank?

On vehicles that have expansion tanks that answer is yes, and because there is no radiator cap.
Now an expansion tank is just that, it’s part of the pressurized cooling system and has what amounts to a radiator cap of its own.
That differs of course from what most of our little marine motors have which is an overflow tank which is not pressurized and is not really part of the cooling system, just catches overflow and allows its return after the engine cools.