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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Replacing an impeller

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Initially Posted - 07/10/2007 : 11:11:14

I've got a Mercury 4hp engine for my Avon. It's stopped peeing the last time I ran it in a bucket to flush it so I need to change the impeller (I presume). Does anyone have a good list of instructions for doing this? I've only read about doing it, but have never seen it done or found a step by step process. My manual doesn't even mention where it is. I presume I have to drop the lower end to do it, but am unsure of the whole process.

Any advice is appreciated.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

Edited by - on

Sloop Smitten
Master Marine Consultant

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USA
1181 Posts

Response Posted - 07/10/2007 : 11:45:59

Generally you follow this sequence.
1. Drain the lower end oil
2. Remove the propeller.
3. Unbolt the lower drive unit.
4. Disconnect the shift linkage to the lower drive unit. How to do this varies according to manufacturer and is probably the toughest part of the job.
5. Remove the lower drive unit and place on bench.
6. Remove the water pump housing taking special care to note how it is assembled.
7. Remove the impeller.
8. Inspect/Replace any seals or bearing that appear worn and clean any salt or debris from the housing and passages.
9. Install new impeller and gaskets making sure you install it according to the notes you took in Step 6.
10. Re-install lower drive unit making sure the water tubes and shift linkage align properly and reattach shift linkage. Use anti-seize compound on any bolts.
11. Refill lower end with oil.
12. Reinstall propeller being sure to lube the shaft with marine grease..
13. Test for proper operation.

Good idea to check the thermostat when you do this as well.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 07/10/2007 : 11:49:05

I recently changed the impeller on an old YachtTwin. The info I found on the web did not cover the XL shaft so dropping the lower unit to get to the impeller was a two stage process, watch for something unique to your XL shaft. The best tip was about reassembly, the impeller is "keyed so it will only go on the shaft with the impeller notch lined up with a flat spot on the shaft, then you insert a small piece of metal bar in the notch against the flat spot and the impeller will then rotate as the shaft does... the tip was to use a little grease on the little key piece and stick it to the flat spot so as to need one less hand. It was good advise. If your engine uses a similar design it may help you too.

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ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 07/10/2007 : 19:52:32

"It's stopped peeing the last time I ran it in a bucket"

Your pump may be fine. Blow some air up the pisser and try running the engine again before you decide you need to take things apart. It's very common for a bit of seaweed or other crud to clog up the hose.

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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 07/10/2007 : 20:08:52

Since this is a dingy motor it probably is not a long shaft so that makes it easier.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 07/10/2007 : 23:14:47

Thanks for all the advice guys. It's quite possible that there was something inside that had bunged up the impeller. I backflushed it and got water running out of about six different places including the right one, no idea if that's good or bad. I'll start it up tomorrow evening and see if it's started peeing again. I'd just as soon not have to take it apart, but I'm not going to be surprised if I end up having to. It came off of a charter boat, and the guy I bought it from never used it once (he bought the charter boat & wanted a RIB & bigger engine). It's surprisingly clean on the inside, so it's possible that it's had decent maintenance, but I'm not holding my breath. The Avon it came with was in pretty good shape though, so who know?

It's not a long shaft, just a 15".

Edited by - delliottg on 07/10/2007 23:15:43

lewalskim
1st Mate

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USA
70 Posts

Response Posted - 07/11/2007 : 06:54:15

David,

I used to take my Honda 9.9 long shaft to an authorized maintainer for about $300 per visit. Changing the impeller was one of the few tasks that was performed.

I then bought a quality maintenance manual that covered my engine and performed the task of changing the impeller in the driveway. It was a little nerve wracking the first time but in the end I think that it was an easy task. I bought a kit from the local Honda dealer that included the impeller and gaskets for about $10.

My telltale water discharge was not flowing at all and I thought that it had to be the impeller. When I got the lower end off, the impeller was fine. I changed it out anyway. I found that my thermostat was badly corroded even though it was only a couple of months old. I flushed the salt out of everything and tossed the thermostat. I find that without the thermostat my engine starts better, idles better, and runs better. I live in Florida and can get away with this.

I do recommend that you get a quality maintenance manual for doing the work yourself. I have found that my sailing friends, engine friends, and some Honda dealers often contradict each other with the advice they give me. So, I get out the book.

Edited by - on

KD4AO
Navigator

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USA
202 Posts

Response Posted - 07/11/2007 : 07:36:06

Mark, would you post the name of your maintenance manaul. Something I will be needing. Thanks

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Sloop Smitten
Master Marine Consultant

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USA
1181 Posts

Response Posted - 07/11/2007 : 07:51:30

<blockquote id="quote">quote:<hr height="1" noshade id="quote">I flushed the salt out of everything and tossed the thermostat. I find that without the thermostat my engine starts better, idles better, and runs better. I live in Florida and can get away with this.<hr height="1" noshade id="quote"></blockquote id="quote">

Mark,
I have been debating the idea of eliminating my thermostat as well. I would not have to run the engine at all if I got rid of it as it would open the water passages to my cylinder head. We have water temperatures that range from about 55 to 75 here in San Diego. I believe the water temps in Florida range from 50 - 85. The water temperature has to maintain a certain temperature to allow the engine to maintain its optimal operating temperature. Not sure of how critical that is in a warm water environment. EPA would probably have a fit but they lost their jurisdiction the day the engine was first sold.

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dave holtgrave
Captain

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USA
427 Posts

Response Posted - 07/11/2007 : 10:14:54

hey mark lewalski

wkere did you find the honda manuals??

i look and i can not find them anywhere.

great job on doing in yourself.

thanks in advance

dave holtgrave
sailing on carlyle lake in southern illinois
5722 sk/tr

Edited by - on

Sloop Smitten
Master Marine Consultant

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USA
1181 Posts

Response Posted - 07/11/2007 : 10:37:48

Dave'
Owners Manuals: (Free)
http://www.honda-marine.com/mar_pages/bf8.aspx

Maintenance Manuals can be purchsed here: (Fee)
http://www.helminc.com/helm/Result.asp?Style=helm& Mfg=AHP& Make=MAR& Model=OUTB& Year=& Category=1& Keyword=& Module=& selected%5Fmedia=& mscsid=NJR7W513SHH79LNF3DT87S54LSGUE6M1

Or you can contact your nearest Honda Marine part supplier and they should be able to order one for you.

Edited by - on

Ed Cassidy
Captain

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USA
365 Posts

Response Posted - 07/11/2007 : 11:09:23

Removing the thermostat is not advised. To prevent excessive wear of internal engine parts, the engine must warm up to operating temperature. Here is a link to site that has a graph of how much wear is caused.

http://performanceunlimited.com/illustrations/thermostats.html

Edited by - on

OLarryR
Master Marine Consultant

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USA
3466 Posts

Response Posted - 07/11/2007 : 11:30:33

I have the Honda engine as well and just purchased the shop manual for it. The owners manual has the info for purchasing the shop manual. i did it from the online website referenced in the owners manual but it also lists the phone number. Probably same links as provided in an above response.

Edited by - on

lewalskim
1st Mate

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USA
70 Posts

Response Posted - 07/11/2007 : 21:04:04

Dave,
The manual I have is available from Boater's World for $35. It's a Honda, 4-stroke 2-130 hp O/B, 1976-1999 by Clymer. Boater's World part # 41-675-0420.

West Marine catalog has a SELOC manual WM part #4633483 for $35.

Helminc.com (who provides Honda shop/service manuals) has part #61ZW900 for the 8 and 9.9 hp models and part #61ZV400 for the 9.9 and 15 hp models. These are each $37. I might get one of these service manuals also.

Ed,
I looked at the site about thermostats that you provided. This information deals with "closed liquid coolant systems". Aren't outboards open cooling systems? I don't know that the information pertains to outboard engines, although it might.

Edited by - on

johnsonp
Admiral

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USA
606 Posts

Response Posted - 07/11/2007 : 21:31:57

I would rather see the piston ring ware chart.
paulj

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dave holtgrave
Captain

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USA
427 Posts

Response Posted - 07/11/2007 : 21:42:50

thanks guys for the addresses

dave holtgrave
5722 sk/tr

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