impeller

MajBach

Chief Petty Officer
Joined
Jun 21, 2003
Messages
564
As I was getting the boat ready for the water this past weekend, I was flipping through the manual and noticed that there was no recommended interval for changing the impeller. What is it? My OB has approx. 400 hrs on it.
 

Navigator

Chief Petty Officer
Joined
Feb 6, 2001
Messages
517
Re: impeller

MajBach,<br /><br />I prefer to do it every other year. If you operate in silty or sandy water conditions, then I'd do it at the start of every season. Its only a $20 part and takes about 15 minutes to change out. Cheap insurance if you ask me.<br /><br />Time and dirt are what kills the impeller. Over time, the rubber will conform to the shape of the housing and loose its flexibility, decreasing it efficiency. It will still pump, but not as much water. The other is dirt. since its rubber, it will eat it up over time. Oh, and running the engine dry will destroy it in about 60 seconds flat!!!<br /><br />Nav :cool:
 

jim dozier

Lieutenant Commander
Joined
Jan 8, 2003
Messages
1,970
Re: impeller

Added benefit of frequent changing. You will be less likey to encounter frozen bolts the next time. If you leave that sucker on for a decade you will have trouble getting it off.
 

Constancia

Seaman Apprentice
Joined
Jan 13, 2004
Messages
35
Re: impeller

Can somebody give me a quick rundown on what's involved in changing the impeller? Where is it located? What do I have to take off/remove to replace it on this engine? <br /><br />Mine seems to be fine, but the engine is four years old now with 450 hours and it's never been changed. Always been run in good water, no sand or silt. I was thinking I'd order the part and do it myself, depending on what all is involved. <br /><br />Thanks!<br />Stuart
 

paxfish

Cadet
Joined
Apr 18, 2004
Messages
8
Re: impeller

Definitely do it - 45 minutes job and $50 is cheap insurance. My first one failed at 400 hours, and stranded me.<br /><br />I'm doing it every season now.
 

jim dozier

Lieutenant Commander
Joined
Jan 8, 2003
Messages
1,970
Re: impeller

All outboards are essentially the same. You remove the bolts that hold the lower unit on. There should be somewhere between 4 and 10 depending on the size of the outboard. You need to disconnect the shift linkage to the lower unit. Each outboard is different in this respect. Usually there is some kind of connector but some have a splined connector that just slips off. The lower unit then falls down (don't drop it) and the water pump sits on top of the lower unit with the drive shaft sticking up through the middle of it. You remove the bolts or nuts holding the pump casing on and there is a rubber vaned impeller inside that gets replaced. Some engines might replace the housing or part of it also. I dont't know the Honda but I know they are similar in principle. Get a manual and go to it. The only problem is frozen bolts. That usually occurrs on motors in salt water that haven't been apart recently, but it can be dealt with patience and a propane torch.
 

Sea_Slueth

Cadet
Joined
Apr 17, 2004
Messages
10
Re: impeller

Jim,<br /><br />Do yourself a favor and purchase the shop manual.<br /><br />I believe the company is called Hall Publishers.<br /><br />I no longer have their number.<br />Call Honda customer service and tell them you need the shop service manual for your engine.<br /><br />It cost about 98 dollars but is well worth it.<br /><br />I was shown how to change my first impeller several months ago. I then did my 2 engines by myself.<br /><br />It is not hard, just need to know what to do.<br /><br />But by all means, change it. Mine were still in tact at 380 hours.<br /><br />I am told the service manual is more complete than other manuals on the market and is the only one recommended by Honda. <br /><br />These were my first engines and with the manual, things are a little easier......
 

MajBach

Chief Petty Officer
Joined
Jun 21, 2003
Messages
564
Re: impeller

Wow - okay, time to change it. But a 15 minute or 45 minute job? Hmmm, think I'll have a pro do it. I have changed the impeller on an old OMC 18hp several times but when I look at this 90 Honda, I dont see any similarities.<br /><br />Really surprising that the manual says nothing about the impellor - don't you think?
 

Sea_Slueth

Cadet
Joined
Apr 17, 2004
Messages
10
Re: impeller

The manual seems to only provide basic information. The job itself is about 60 months.<br /><br />If you can, try to see if someone could show you how to do it.<br /><br />Where do you live? Maryland here.....
 

Constancia

Seaman Apprentice
Joined
Jan 13, 2004
Messages
35
Re: impeller

45 minute job... uh-huh. Well, it seemed that way at first. Lower end slid right down, no problems. Was able to easily replace the impeller and gaskets. But... (here's the big but), I'm unable to get the lower unit back on! The drive shaft is splined at one end (but not keyed, as best I can tell). I can't seem to get it to seat. I've tried rotating the shaft in small increments, but still no luck. Anybody have any suggestions or know any secret tricks to get this lower unit back into place? It's making me crazy! <br /><br />Also, shaft is not bent or anything. I took great care taking it apart. Greased the splines quite well. It seems like the silly thing should just slip back in there, but it won't. Help!?<br /><br />EDIT: Thanks, no need to respond. Tried bumping the starter a couple of times and this let me slip the lower unit back up into place! All better now!! :)<br /><br />Stuart
 

Hawaiian

Petty Officer 2nd Class
Joined
Feb 4, 2003
Messages
111
Re: impeller

Stuart, how many hours were on the meter when you did the change and what was the condition of the impeller?
 

radsrh

Petty Officer 1st Class
Joined
Oct 30, 2002
Messages
250
Re: impeller

Are you sure it was the drive shaft causing the problem, or was the water tube that was not properly in place?
 

Constancia

Seaman Apprentice
Joined
Jan 13, 2004
Messages
35
Re: impeller

Perry,<br /><br />I have 450 hours on my motor over a five year period (June makes five years I've owned the boat, bought it new in 1999). Overall, the "pee" stream seemed a little weak, but was still moving water quite well. When I spoke to the Honda dealer about it, he said they recommend every 3 years for replacement and that I was running on borrowed time. I was also concerned that living here in Arizona, that the heat and hot, dry climate might have dry rotted the rubber. <br /><br />However, the old impeller was in good shape. There was minor wear on it and some of the fins looked like they might be cracking just a tiny bit at the stress points where they bend within the housing. There was no pitting, missing pieces, or other damage. It was still supple and flexible and in a lot better shape than I figured it would be. I kept it as a spare. I also replaced all the gaskets that came with the impeller kit ($42). There is a paper-type gasket that goes on the bottom of the housing and an oblong shaped O-ring gasket that seats in a groove on top of the plastic housing. <br /><br />Since I had the lower end off, I drained and refilled the gearbox with a good synthetic gear oil. This was much easier to do with the lower end laying on its side and I was sure that I got it completely filled. Last time, with it on the boat, I had to use a pump to fill it from the bottom drain hole until it started running out the oil level check port. It was a pain and I wasn't sure I had a good fill on it. The gear oil I replaced was in good shape overall, black and stinky as usual, and only a tiny bit of yellow egg nog in it, which could just be moisture from condensation, rather than a leak. I'll see what it looks like next time, but expect about the same.<br /><br />radshr - It was definitely the drive shaft that wasn't lining up correctly. There is a rubber bushing on the water shaft and I lubed that up to help it slip into place. Once I bumped the starter a couple of times, the lower unit slid right into place with no hesitation. Just a matter of getting those splines on the end of the drive shaft to line up correctly with the upper end. <br /><br />After I bolted it back together, the true test -- I put the mickey mouse ears and hose to it and ran it. The "pee" stream was restored to very strong pressure, like an 18 year old after a 12 pack of beer! :D Motor shifted between forward and reverse with no problems. Ran it for about 15 minutes and all seemed good! I'm ready to go chase marlin and dorado in Baja in June!<br /><br />Here's a picture of my tin can. I just installed a set of Taco Sport Slam Outriggers on the T-top and am dying to try those out trolling!<br /><br /> http://members.cox.net/sburnett22/InSlip.jpg <br /><br />Stuart
 

jim dozier

Lieutenant Commander
Joined
Jan 8, 2003
Messages
1,970
Re: impeller

Mackerelena, I would think that filling up a gearcase on its side, while convenient, is not appropriate. The oil level should just come to the bottom of the vent screw (top screw). Unless you tipped it up to drain the extra (defeating the purpose of doing it on its side) you may have too much oil in there and I wonder if you are in danger of blowing out a seal.
 

Constancia

Seaman Apprentice
Joined
Jan 13, 2004
Messages
35
Re: impeller

I hadn't considered that, Jim, thanks. I did tip it up after filling it and placing the bottom screw back in it and it seemed to be okay, but perhaps, I'll loosen that check screw on the top and burp it just to make sure it isn't overfilled. If I recall, the gear oil should just seep out a bit when you pull that screw.
 

Skinnywater

Commander
Joined
Mar 7, 2002
Messages
2,065
Re: impeller

You will be less likey to encounter frozen bolts the next time.<br />
Beautiful point jimd. <br /><br />At about 80 hours I had to take my jetpump off to diagnose a rattle. A healthy dose of marine grease on my driveshaft splines cured the noise. I inspected my waterpump impeller and found it pristine. <br />At this past 200 hour, I regreased the driveshaft splines again and inspected the waterpump impeller. Again it was supple and in beautiful condition. The stainless liner was very smooth.<br />However, the rubber bushing at the water pipe as well as the housing perimeter seal were showing some deterioration. Either of these fail, the result is nearly the same as a blown impeller.<br />For me, it'll go another 100 hrs.<br /><br />I have 3 additional labor proceedures to inspect my waterpump, mine being a jetpump over a prop. The entire inspection takes 2-3 hrs., done meticulously.<br /><br />My Honda Marine factory repair manuel is about an inch and a half thick with and covers every nut and bolt top to prop on my BF50. At $40 it's been an invaluable tool.
 
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