Does anyone have any tricks to tell if a raw water pump has gone bad? 350 FWC Merc
Circulation Pump
- Thread starter dwna1a
- Start date
Stray Current
Well-Known Member
- Oct 27, 2019
- 1,963
- Boat Info
- 2007 260DA
- Engines
- ‘07 6.2 Horizon MPI / ‘24 SeaCore Bravo III - ‘07
Kohler 5ECD
Assuming you have alphas on an 88 300 weekender? Is it overheating and how hot are the exhaust elbows?
BillK2632
Well-Known Member
Initially you will see the temp start fluctuating, especially when coming back to idle after a higher speed run, engine will heat up a little because the pump is not pumping well at low speed. Also, as mentioned the riser temp get's hotter. These are non-catalyst motors, so the risers should be warm, not hot, should be able to lay your hand on them.
If the impellers are more than 3yrs old they would be suspect.
If the impellers are more than 3yrs old they would be suspect.
Stray Current
Well-Known Member
- Oct 27, 2019
- 1,963
- Boat Info
- 2007 260DA
- Engines
- ‘07 6.2 Horizon MPI / ‘24 SeaCore Bravo III - ‘07
Kohler 5ECD
Just to clarify, are you talking about the belt driven circulator pump, or the impeller down in the outdrive?
Your title says circulator pump, but your first post says raw pump
Your title says circulator pump, but your first post says raw pump
markrsimon
Active Member
Are we sure this is FWC with a heat exchanger? Im thinking for the style and age boat - it would be raw water cooled.
Previous post says you picked up a 160 thermostat. What temps are you hitting on the gauge? Did you put a 160 in each engine, and only one is showing issues?
Previous post says you picked up a 160 thermostat. What temps are you hitting on the gauge? Did you put a 160 in each engine, and only one is showing issues?
techmitch
Well-Known Member
- May 1, 2008
- 8,395
- Boat Info
- 1999 270 DA
- Engines
- Twin 4.3s W/Alpa I Gen II's
Isn't a weekender strightdrive's/shaft's?
techmitch
Well-Known Member
- May 1, 2008
- 8,395
- Boat Info
- 1999 270 DA
- Engines
- Twin 4.3s W/Alpa I Gen II's
Mitch is correct about the straight shafts. Engines don't really factor in, though - but based on his signature they're small blocks.
Sorry 350’s straight inboards.
I went out to do some bottom cleaning. No issues. On the way in it pegged out. I had some belt noise on start up. I checked the belts and they are fine. I did find the overflow hose had come off so I reconnected and replaced the antifreeze. Impeller is two years old and should be replaced, I hate it but I’m going to do it. The pumps appear to be original. I’m going to do the tstates and housings next week.
I went out to do some bottom cleaning. No issues. On the way in it pegged out. I had some belt noise on start up. I checked the belts and they are fine. I did find the overflow hose had come off so I reconnected and replaced the antifreeze. Impeller is two years old and should be replaced, I hate it but I’m going to do it. The pumps appear to be original. I’m going to do the tstates and housings next week.
Pegging all of sudden means something happened. How much AF were you down? Did replacing the AF solve the issue?
Is this on one engine only, I assume?
If you take the inlet hose off at the heat exchanger, since you have an on engine pump, you run the engine at 1,000RPM and collect the water for 15 seconds. You should get roughly 7-1/2 quarts. If you're getting that, the impeller and impeller housing/wear plate is fine.
What "pumps" appear to be 35 years old?
Is this on one engine only, I assume?
If you take the inlet hose off at the heat exchanger, since you have an on engine pump, you run the engine at 1,000RPM and collect the water for 15 seconds. You should get roughly 7-1/2 quarts. If you're getting that, the impeller and impeller housing/wear plate is fine.
What "pumps" appear to be 35 years old?
No replacing the AF did not solve the problem and the heat exchanger was low but not seriously low. I topped off the system and ran her at the dock. She overheated again in the slip. Pulled the strainer and opened the seacock, I had great flow. I’m going back on Sunday to check the risers. I also want to see the output on the exhaust to be sure the water is flowing well
My raw water pumps are about two years old, both were replaced due to the bearing seals were leaking.
Ok folks this is what I have to report.
Risers and manifolds were cool to the touch and the output at the exhaust was pretty normal.
All hoses but one were the same. The one hose leads from the circulation pump to the bottom housing of the thermostat was very hot.
Any guesses would be great. I’m still looking at the pump or the thermostat
Risers and manifolds were cool to the touch and the output at the exhaust was pretty normal.
All hoses but one were the same. The one hose leads from the circulation pump to the bottom housing of the thermostat was very hot.
Any guesses would be great. I’m still looking at the pump or the thermostat
Bill Curtis
Well-Known Member
- Mar 24, 2022
- 1,014
- Boat Info
- '95 220 Overnighter
454 Mag. Bravo3 w/ 2.0:1 gears and 28 pitch props
- Engines
- 454 Mag Bravo3. 2.0:1 ratio gears w/ 28 pitch props
Closed cooling systems are basically an automotive type system and pretty simple and very reliable. Only parts that are common offenders are the stat, circ pump and radiator cap (then you have leaking head gaskets and the like). Complicated part is raw water part of the exchanger and the crazy hose system for the manifolds, single point dains and such.
I would change the stat 1st. If you overheated the engine, that can (and will) kill a stat. On an overheat, I always changed them. A bad radiator cap not holding pressure can cause some engines to run hot.
But, since you are draining the AF to do that, why not change the circ pump too, since it's already been drained. Some circ pumps have been known to fail at the impeller hub pressed onto the shaft, causing the impeller to "free wheel" on the shaft and causing what you are seeing.
