I had some slightly reduced cooling the other weekend, thought I'd investigate. I've owned the boat 18 months, replaced 2 impellers which I carefully inspected and none had missing pieces (both separated at the hub - yanmar branded).
How many impellers?
- Thread starter flightlead404
- Start date
Wow, that is a lot of rubber bits! Where did you dig those out of (you indicate one of the ones you inspected had any missing vanes)…was this bunch of rubber in the HX?
Something has to be wrong I would think to destroy a new impeller in 18 months. As @sail sfbay asked, hours may be more telling than time.
Any chance that the impeller ran dry for any period of time? That could mess one up really quick…maybe someone forgot to open the cooling water valve, and opened it after things got warm? Or the intake was plugged with marine goodies ?
Greg
Something has to be wrong I would think to destroy a new impeller in 18 months. As @sail sfbay asked, hours may be more telling than time.
Any chance that the impeller ran dry for any period of time? That could mess one up really quick…maybe someone forgot to open the cooling water valve, and opened it after things got warm? Or the intake was plugged with marine goodies ?
Greg
Those bits, and its a LOT more than a handful, are NOT from my impellers!
I dug those out from the last 1/2" of hose and from the input side on the end cap of the heat exchanger. Man it was packed solid in there!
I have replaced two impellers, both failed at the hub and I inspected them carefully for missing bits. To be clear, none of the impellers I replaced had missing bits. The rubber essentially separated from the hub, but was fully intact. I'm now wondering if mine failed in that manner because of excessive back pressure. Frankly I don't know how it was cooling at all.
I've had the boat a bit over 18 months and have traveled from Ft Pierce to Ft Lauderdale, to Hilton Head, to Key West, and back to Hilton Head in that time, with at least 20 solid days of motoring.
I'd never taken the input hose side off the heat exchanger before. Last time I ran some Barnacle buster through I coupled in at the other end of the hose. This time I really wanted to dig in and investigate what was happening. I've been getting a little steam in the exhaust, more than I expected, and the recent over temp alarm.
This mess has to have been building up for years!
I replaced one shortly after I got the boat, and another one a month or so ago. Couple hundred hours or less. Yes, high frequency.
Purchased our 1991 boat in 2002 without inspecting the impeller. Yanmar had about 650 hours of run time when we purchased her. Decided last year to check the impeller with about 2,200 hours of run time. Impeller looked brand new, but replaced it anyway and will keep it as a spare.
"a lot" meaning "a lot of hours per impeller" or "a lot of impellers for than many hours". Its less than 90 hours per each actually. Neither made it past 9 months. Seems like a very short life for an impeller to me.
What is a reasonable value for X?
On my 3GM30F Yanmar, I had 1 Yanmar impeller separate from the hub also. It happened about 4 years ago.
The hub just spun and the impeller just sat there. As to the pin, it stayed in the slot on the pump shaft and spun the hub. It‘s a rare occurrence, I believe, as my Yanmar dealer said he only saw this happen once before.
I keep extra(s) on the boat. A new one and a couple of the replaced ones also. In a pinch they will work. And you just have to constantly check the flow of water coming out the exhaust. I check by sight and by sound.
The hub just spun and the impeller just sat there. As to the pin, it stayed in the slot on the pump shaft and spun the hub. It‘s a rare occurrence, I believe, as my Yanmar dealer said he only saw this happen once before.
I keep extra(s) on the boat. A new one and a couple of the replaced ones also. In a pinch they will work. And you just have to constantly check the flow of water coming out the exhaust. I check by sight and by sound.
Do you mean the splined shaft the impeller turns on? Or is there a pin
Me too. I don't keep used ones, I keep three new ones. They are cheap enough.
I'm amazed given the blockage, that I was getting a lot of water through the exhaust. I will restart the engine in a couple of hours and compare (qualitatively) the volume of water at idle.