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Old 15-08-2022, 16:30   #1
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Water pumps on outboard driven cats

Just finishing a routine haulout of my Maine Cat 38. The haulout was primarily for fresh bottom paint, but of course is an opportunity to inspect everything and do preventative maintenance.

My habit is to change out the water pump impellers of the two Yamaha T9.9s engines, this being easy to do while the boat is on the hard. After 300 plus hours the water pump impellers and housings were pristine, showing little or no wear. At the previous haulout I observed similarly little to no wear with more than 500 hours on each engine.

For discussion, how frequently to you change the water pumps on your outboard powered catamaran...

It is looking like 500 hours or more is possible. So far for me changing these water pumps is easy and not expensive insurance that I will likely continue at each haulout.
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Old 15-08-2022, 16:56   #2
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Re: Water pumps on outboard driven cats

Each haul out sounds reasonable, it is also beneficial to regularly split the legs to prevent them fusing together. 500hrs is probably pushing it.
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Old 16-08-2022, 00:18   #3
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Re: Water pumps on outboard driven cats

What a sensible bunch on CF. I agree completely, replace when you antifoul because you should and because it keeps the legs nice and free to move.

I had an Evinrude 8hp I was gifted. It stayed in my shed and I never pulled the leg. Ionly used it a little and it stopped pumping. Then I couldn't get the leg off. The bolts I could remove but in the end the shaft would not release from the crankshaft. I tried everything - diesel, kero, heat - nothing worked.

In the end I had to throw it away because I had wrecked the motor trying to remove it. So take the leg off, replace the impeller and grease the bolts AND shaft as you re-assemble.

cheers

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Old 16-08-2022, 00:39   #4
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Re: Water pumps on outboard driven cats

Tefgel mating surfaces and bolts when you have the leg apart...
Regarding replacing at each haul out, well depends how often you haul her out, no? I think engine hours is a good indicator, especially if you pull them up when not in use..
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Old 16-08-2022, 13:13   #5
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Re: Water pumps on outboard driven cats

I put a light coating of marine grease on the leg joints, especially the locator pins. I was concerned maybe this might compromise electrical conductivity resulting in galvanic corrosion. The anodes are in good shape. I will see how it goes.
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Old 17-08-2022, 05:46   #6
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Re: Water pumps on outboard driven cats

Tef-Gel the threads and a tiny bit on the mating surfaces. Absolutely correct. Great post above.
You can put Tef-Gel on your battery connections because it squeezes out when you tighten down.
Unlike grease, itís very resistant to wash out.
I hate outboards. If you have a seized bolt you need a plumber torch and you have to heat it till the paint blisters. Heat, beat, Pb blaster or weasel pee. Yuck.
We bought a new Yamaha 25 which ran ok but came with a broken bolt in the head and a fuel filter that was very difficult to change or drain. Gave away a Honda to keep my sanity.
We have a catamaran friend who changes his impeller in the water as his dinghy fits underneath. Iíve donated enough tools to Neptune.
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Old 17-08-2022, 06:02   #7
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Re: Water pumps on outboard driven cats

Or you can do like me and change them in the water. And lose a lower unit into the drink because you were too cocky from doing it so many times before.

99% of the time: remove all bolts and tap, tap, bang, bang! Why won’t this thing come off?? Also because my previous outboards were all old.

Me last time: remove all bolts, grab the wood piece and hammer to tap, before you touch it, watch it miraculously fall off with no coaxing and do a straight shot down the outboard well and to the bottom.

I traded someone an air conditioner to fish it out (by swimming) and it took hours.

Lesson? Don’t be cocky and put a safety line on any damn thing that has the potential to get away from you. Ha ha.

Incidentally, that was like 4 years, 1000 nautical miles on the engines and the impellers and housings appeared completely fine. Original impellers.
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Old 17-08-2022, 07:31   #8
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Re: Water pumps on outboard driven cats

Yamaha mechanic told me heíd never seen an impeller fail that was less than 3 years old, so that was his recommendation. I think a lot has to do with the hours put on the engine. Lots of hours it should be changed out more often. If let sit without running for an extended time, it should be changed.
We pull the lower units on the mother ship by sliding the dinghy under the lower units while the outboard is tilted up.. No loss of tools or lower unit yet as the dinghy fits under the lower unit.
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Old 17-08-2022, 08:15   #9
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Re: Water pumps on outboard driven cats

Quote:
Originally Posted by Manateeman View Post
Tef-Gel the threads and a tiny bit on the mating surfaces. Absolutely correct. Great post above.

You can put Tef-Gel on your battery connections because it squeezes out when you tighten down.

Unlike grease, itís very resistant to wash out.

I hate outboards. If you have a seized bolt you need a plumber torch and you have to heat it till the paint blisters. Heat, beat, Pb blaster or weasel pee. Yuck.

We bought a new Yamaha 25 which ran ok but came with a broken bolt in the head and a fuel filter that was very difficult to change or drain. Gave away a Honda to keep my sanity.

We have a catamaran friend who changes his impeller in the water as his dinghy fits underneath. Iíve donated enough tools to Neptune.

Mark
Regarding tools for neptune, do you know the trick with an inverted umbrella underneath? Very helpful.
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Old 18-08-2022, 01:15   #10
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Re: Water pumps on outboard driven cats

Quote:
Originally Posted by Franziska View Post
Regarding tools for neptune, do you know the trick with an inverted umbrella underneath? Very helpful.
And tradition says no use for an umbrella on a boat - Brilliant, always have one on board
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Old 19-08-2022, 06:32   #11
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Re: Water pumps on outboard driven cats

Franziska, Brilliant. I find you have a very practical approach to boating, as shown in this post and many others.
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Old 19-08-2022, 12:19   #12
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Re: Water pumps on outboard driven cats

Thanks guys, thought this is a common thing
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