After un-winterizing my boat this spring, my generator (Northern Lights 673) started overheating. I had a strong stream of raw water coming out of the exhaust, so I knew it wasn't the impeller. After several dock conversations with other boaters, we came to the conclusion that it was probably the thermostat. This is the mechanically operated device that is in the engine block near the water pump that circulates antifreeze/water throughout the block. In the Norther Lights, it is located between the heat exchanger and the block.
First, disconnect the generator from its battery and all electrical sources. Then, you have to remove the soundproofing enclosure from the side of the engine where the heat exchanger is located (opposite the dipstick and oil filter). This might be tricky, because this side of the engine in not routinely serviced. In my installation, I also had to remove the antifreeze expansion tank because it is screwed to the sound enclosure on this side.
Next, you will need to open the petcock above the dipstick to drain the antifreeze from the engine. (you should remove about a quart). Next you need to loosen and remove three nuts and five bolts that secure the heat exchanger to the block. After these have been removed the heat exchanger will slide away from the block on the three remaining 4" studs (after you tap it gently to break the gasket seal).
If you work gently, you will not have to disturb any of the other plumbing or electrical connections to anything. Everything should "stretch" enough to get access to the thermostat. That's the good news.
Now for the bad news. As you attempt to slide the heat exchanger far enough away from the block to remove the old thermostat and mounting spring, the heat exchanger will bump into the starter solenoid mounted on top of the starter. So, you must remove the two bolts that hold the starter to the flywheel housing, then partially remove the starter. You only have to let the starter "sag" on its wires about 1/2" for the heat exchanger to clear. Just pull the heat exchanger far enough away from the block to remove the spring, then the old thermostat. Install a new one (mine cost less than $20), then the spring and push the heat exchanger back against the block. Be careful when tightening the three nuts and five bolts. Torque them a little at a time in a standard torquing order (from the center out). Since they are small, they can easily be stripped.
Now put everything else back together and top off the antifreeze/water at the proper ratio. Open the raw water seacock, connect the battery and crank it up. Mine runs steadily now with the water temp gauge showing 190 degrees F.
All of this too about 4 hours in the prone position with my head down in the locker that houses the generator. Let's hope I get another 700 hours before the new thermostat fails.
Agaliha
First, disconnect the generator from its battery and all electrical sources. Then, you have to remove the soundproofing enclosure from the side of the engine where the heat exchanger is located (opposite the dipstick and oil filter). This might be tricky, because this side of the engine in not routinely serviced. In my installation, I also had to remove the antifreeze expansion tank because it is screwed to the sound enclosure on this side.
Next, you will need to open the petcock above the dipstick to drain the antifreeze from the engine. (you should remove about a quart). Next you need to loosen and remove three nuts and five bolts that secure the heat exchanger to the block. After these have been removed the heat exchanger will slide away from the block on the three remaining 4" studs (after you tap it gently to break the gasket seal).
If you work gently, you will not have to disturb any of the other plumbing or electrical connections to anything. Everything should "stretch" enough to get access to the thermostat. That's the good news.
Now for the bad news. As you attempt to slide the heat exchanger far enough away from the block to remove the old thermostat and mounting spring, the heat exchanger will bump into the starter solenoid mounted on top of the starter. So, you must remove the two bolts that hold the starter to the flywheel housing, then partially remove the starter. You only have to let the starter "sag" on its wires about 1/2" for the heat exchanger to clear. Just pull the heat exchanger far enough away from the block to remove the spring, then the old thermostat. Install a new one (mine cost less than $20), then the spring and push the heat exchanger back against the block. Be careful when tightening the three nuts and five bolts. Torque them a little at a time in a standard torquing order (from the center out). Since they are small, they can easily be stripped.
Now put everything else back together and top off the antifreeze/water at the proper ratio. Open the raw water seacock, connect the battery and crank it up. Mine runs steadily now with the water temp gauge showing 190 degrees F.
All of this too about 4 hours in the prone position with my head down in the locker that houses the generator. Let's hope I get another 700 hours before the new thermostat fails.
Agaliha
