Hello All
The following is something that occurred with our Northern Lights gen-set. and I thought this might be of help should the same thing happen to someone else. Especially on a trip!!!!
The raw water pump was leaking, and it was discovered there was a chunk of blade missing on the raw water impeller. While the boat was laid up at Seaview West at Shilshole Seattle, I had the pump seals and impeller replaced by Paul at Northern Lights, just down the street from Shilshole. After the pump was re- installed and boat back in the water, I ran gen-set to test for any leaks after replacement of water pump seal and new impeller. Everything seemed fine for around ¾ of an hour, until ready to shut the unit down when I noticed steam coming from the gen-set. After shutting the unit down, I found raw seawater accumulating in and around the base of the unit and in the bilge. Further examination revealed that the cooling system recovery bottle was full of seawater and was overflowing out into the gen-set box
See Northern Lights Parts Catalog M673LD2 page 3-0 for descriptions
After talking to Paul at Northern Lights the cause is most likely either some type of obstruction restricting seawater flow through the heat exchanger, causing a back pressure in the heat exchanger and compromising the seal at clamps (14) on the rubber boot, thus allowing an intermixing of seawater and coolant, or one or both clamps (14) are simply loose.
The fix was as follows:
1. Drain remaining water in block through the valve near oil dip stick.
2. Remove forward rubber boot joint (12) from exhaust manifold expansion tank (1).
3. Pull out heat exchanger (11) from exhaust manifold expansion tank (1).
4. Inspect and clean tubes in heat exchanger (11)
5. Remove rubber boot joint (12) from the other end of exhaust manifold expansion tank (1).
6. Inspect exhaust elbow (6). Note: On the top of the elbow where the rubber boot joint attaches, inside the hole there could be blockage here or inside the elbow.
7. Clean and dry back rubber boot joint (12) and replaced onto exhaust manifold expansion tank and exhaust elbow fittings.
8. Replace the heat exchanger (11) into forward end of exhaust manifold expansion tank (1) with the holes in the heat exchanger cylinder pointing down and allowing about 2MM of the heat exchanger cylinder to protrude from expansion tank. This allows for the other end of the heat exchanger cylinder to slide into place inside the back rubber boot joint that is already in place on the expansion tank.
9. Clean and dry the forward rubber boot joint (12) and placed on the forward side of the expansion tank (1).
10. Tighten forward and back rubber boot joint clamps (14) that create the seal on the heat exchanger cylinder. These are the clamps closest to the elbows of the rubber boots (these must be tight to create the seal preventing seawater and coolant intermixing), not the clamps that hold the boots to the expansion tank. Then tighten the clamp holding the back rubber boot to the exhaust elbow (6).
11. Tighten both rubber boot joint clamps at the expansion tank (13).
12. Fill through the exhaust manifold expansion tank (1) filler cap fresh water until tank and block full. Then drain out all water, repeated 3 times.
13.Fill block and expansion tank with fresh water and with filler cap off, run engine with fresh water in expansion tank and block until water is hot and check for leaks, make sure water level at filler is not rising. Stop engine, drain, repeated 3 times. Check for leaks.
14. Drain all water from expansion tank and block. Replaced with just under ½ gallon 50/50 mix of Havoline Extended Life Anti-Freeze / Coolant, replace filler cap.
15. Run gen-set for 1 hour with at least 3500 W load, check for leaks and any sign of seawater back filling into cooling system recovery bottle. Watch for water temperature to remain at or under 180 F for entire run.
16. Spray all surfaces that were exposed to salt water with Salt Away and wipe clean. Electrical connections spray with WD-40. Engine mounts spray with WD-40. Bilge areas pump dry and wiped clean.
17. After gen-set run and after cool down, check fluid level and add 50/50 mixture to recovery bottle.
Lessons I learned because of this: Anytime there is a chunk of impeller missing, find where it went. Clean the heat exchanger and exhaust elbow. As per owners manual instructions, remove and clean heat exchanger once a year but In addition to this, inspect exhaust elbow for obstructions and Inspect raw water impeller. Although my problem was caused by pieces of impeller clogging the exhaust elbow, it is a very good idea to regularly check rubber boot joint clamps (14) are tight. Should one or both of these become loose, the raw water and engine coolant will intermingle causing the engine to flood with seawater.
SteveH