True Baker, true.
But, disassembling the aftercooler (which really should be pressure tested when disassembled), or removing the hose and "fishing out" the small pieces through the opening, sounds like much more work than just opening a strainer and removing the bits. Now having the space to place a strainer between the raw water pump and the aftercooler can prove difficult, especially if on the Cummins 6BTA with an installed fuel cooler between the pump and aftercooler. I removed my fuel cooler and now there is probably room, so I am considering it, although so far, there has not been an impeller issue. Only takes once though.
Changed my impeller yesterday. I also have the Cummins 6BTA 330 hp and changed over to the SMX 1730 pump a few years ago. Nice pump, definitely better built compared to the Sherwood (stock one). The old impeller had 2 years of use, and almost 500 hours on it. On close examination, the old impeller looked "almost new".
During the winter, I don't use the boat. I store the engine with a mixture of freshwater and "salt away" in the raw water system. The local dock water is shut off to prevent freezing, so if I want to keep the saltwater out of my system, no running of the engine during the winter down time. So, I "bump" the starter every month to move the impeller to prevent it taking a set. This seems to be working??
I think I probably could go 3 years if I removed the pump cover annually to visually inspect the impeller condition. However, being somewhat conservative, I think I will do the annual inspection and stick to the 2 year interval.
Richard C., how long do you think (hours) before the pump might need a rebuild or are you going to wait for a visual signal (like a leak)?
I've upgraded the original Sherwood seawater pump on our Cummins 6BTA 5.9 M3 to a Seaboard Marine SMX 1730 pump. Replaced the impeller every two years and 1600 hours. So far (two replacements) it has always looked OK. Thinking I might go to annually.
I believe it is Ted (O C Diver) that added a strainer between his raw-water pump and heat exchanger. His set up is designed to catch broken pieces of impeller before migrating to the heat exchanger, etc. Ted?
I change my impellers annually. Shutting down my single engine could put me at great risk in some of the places I go. Impellers are another item in the overall cost of boating that cost not nothing. Here are some pics from the strainer on my generator. Easy to shine a light in it each morning when I check the oil.
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Ted
Which is why twins are better than singles.
As someone here recently said and I paraphrase, "I only need one running engine and that's why I have two".
If you can't dock a single engine boat and you don't do preventative maintenance well, you should have two engines in a displacement hull boat.
Ted
To me it depends on where you boat. I'm a strong believer in Murphy's law. If I'm mostly boating in places where if an issue crops up, I can sit or drop an anchor for a few minutes while I sort the issue out, I'm content with a single. If I'm regularly in tight or high traffic places, I'd rather have twins, as it gives the option of shutting one down and sorting out the issue either underway or in a few minutes when in a better spot.
Of course, no amount of systems redundancy is a replacement for doing proper maintenance. It doesn't matter if you have 1 or 5 of something, it's still good to know it'll all work when you want it to.
There are certainly cruising parameters that justify a twin engine or single and a wing engine. I'm not crossing an ocean with a single although it has been done. For most coastal and inland cruising, between a generally benign environment and the availability of tow boats, I find the exceptionally low risk acceptable, but then I'm OCD on PM.
Ted
FWIW, most engine shutdowns I've seen have not been maintenance related. I've seen a sudden overheat due to a stuck thermostat (no prior warning, cooling system was well maintained). Sudden loss of raw water flow due to plastic bag sucked into thru hull. Sudden loss of engine due to fuel pump failure with no prior symptoms. Or this summer's failure. Sheared teeth on a plate in the trans reduction planetary on the port side. No noises, no warning, just sudden loss of power output from the trans. Stuff like that. Some of those would have required a tow on a single, some wouldn't, but all required a shutdown to assess / resolve the issue.
First, remind me not to cruise near you. I can't afford that much bad luck so close to me.
Regarding the above, my OCD at refit addressed some of these issues.
Don't worry too much, most of those issues weren't on a boat in my care. And they were spread out over quite a number of years. As far as your point about making changes at refit, I absolutely agree that if I were doing the systems design on a boat, there would be some things I'd do differently, particularly around trans ratings (although I do have a good bit of headroom in the ratings on mine, so I'm not sure how much that really impacts the failure). As well as stuff like water intake design, ease of impeller changes, etc.
But on a boat where I'm not doing a heavy refit right now, there are certain things I'm stuck with. I do plan to change up my engine water intakes a bit in the next couple of years, however. The current scoops have an internal screen, which means they can't be un-clogged from inside the boat if necessary. I'd rather ditch the screen and be able to poke down through the thru hull to clear one. And I'd rather clean trash out of the strainer in the boat than from the outside where it's harder to get to.
My raw water intake has an external perforated screen with 1/8" holes. It's oversized to eliminate vacuum from drawing things completely over it.