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Author Topic:   Oil/Fluid Leak from Lower Unit
Legobusier posted 04-07-2004 09:02 PM ET (US)   Profile for Legobusier   Send Email to Legobusier  
Hi all,

As you guys know by now, I'm a newbie, so bear with me if this is a really stupid question.

I have noticed a small amount of oil leaking from the cooling intake ports of my 1998 Honda 90-HP after it is in the full up (trailer) position for a few days. It's not a ton of fluid for what it's worth, but it certainly does not look like it's supposed to be there. Is this normal or something I need to give some attention.

For what it's worth, the oil (I assume it's oil as it has that consistancy, however it's blue?) is nice and clean.

Here's a photo:

Also, since this only happens when the engine is stored in the full up position this brings me to another question - what position SHOULD I store the engine in when on the trailer? Not on the road, but on the trailer in my driveway.

Thanks all,

captreils posted 04-07-2004 09:29 PM ET (US)     Profile for captreils  Send Email to captreils     
That IS gear lube, probably Mercury High Performance gear lube because of it's bluish green color. Your lower unit is supposed to be sealed air tight. You probably have a leak under the water pump base. A simple pressure test would show the bad seal. If you haven't changed your water pump yet now would be a good time.
Legobusier posted 04-07-2004 10:13 PM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Thanks for the reply Pete. Is this bad as in "I have a splinter" bad; or bad as in "we may have to take off your foot" bad. :)

I guess what I'm REALLY asking is it safe to run the boat like this before I fix it or do I risk really jamming something up?

Also, do you think I need to replace the entire water pump, or just the impeller?


Lars Simonsen posted 04-07-2004 10:25 PM ET (US)     Profile for Lars Simonsen  Send Email to Lars Simonsen     
If you have a leak in your lower unit, I would have it checked out before I ran it. If oil can get out, I presume that water can get in. If the oil is clean and clear, you don't appear to have any water in the oil yet. But once you have water in the oil, it doesn't take much time to do a lot of damage to your lower unit.

Also, I second captreils' suggestion that you replace your water pump if you have not already done so. That's routine maintenance, and it may give you (or your mechanic) the opportunity to solve the oil leak problem, as well.


jimh posted 04-08-2004 07:29 AM ET (US)     Profile for jimh  Send Email to jimh     
The picture (hyperlink above) does appear to show lower-unit oil leaking. There are two seals in the lower unit:

--propeller shaft seal
--upper drive shaft seal

I would guess that you have a bad seal at the upper drive shaft. This will require the removal of the lower unit for service. Dropping the lower unit is not a big deal--it is done annually by many for service to the water pump.

Your biggest problem will be finding a HONDA part and a mechanic!

Also, it could be a case of something spilled into the power head area that has seeped down the mid-cowling and into the lower leg.

P.S. This should be in the MODS/REPAIRS forum!

jimh posted 04-08-2004 07:32 AM ET (US)     Profile for jimh  Send Email to jimh     
If your trailer set up provides enough clearance, I would stow the engine in the normal operating position, or near that position.

I generally keep my engine tilted down in storage, resting on the highest point of the trim cylinders. On my engine (Yamaha) and many others, you will find three hydraulic cylinder rams. One is used for the tilt range, and two are used in the trim range.

On advice from LHG, I leave my engines parked just at the top of the trim range. This provides enough ground clearance for travel on the highway on the trailer, too, although you do have to look ahead for driveway ramps that have poor slopes to them (so you don't scrape the skegs on the pavement).

Legobusier posted 04-08-2004 07:44 AM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Thanks for the replies guys. Is this something I can do myself of do I need to have it done? I'm pretty handy and used to rebuild (auto) engines, so I know my way around a wrench, but if it's real delicate or requires specialized tools I guess I'm out.

Also, do I have to go to Honda for parts or would West Marine, etc carry what I need - which I presume is a new impeller and new seals....anything else?

SS17 posted 04-08-2004 01:03 PM ET (US)     Profile for SS17    

I am almost positive that the lower units, and for that matter, the trim tilt assembly are mercury parts. Somebody here should know that, and hopefully will confirm that we can get merc 115 lower unit parts for our hondas. I have a friend with a 115 merc who will have her whaler at my house next week, and I am going to compare the parts.

Sorry to see you have a lube leak. I wouldn't run it until I found out why it was leaking and fixed it. Have you checked the fluid at the lower drain plug? If water has been pulled in as the fluid went out, you will get water out of the lower plug. At the very least, check that often if you run the boat.

You won't find the parts you need at West or the like, but you can get merc parts pretty easily at dealers, or online.


Legobusier posted 04-08-2004 01:17 PM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Just got back from my friendly local Honda dealer with a nice small expensive box of parts....not sure what they all are yet, but I'll find out soon enough :) I got a water pump rebuild kit and new seals and gaskets, etc.

If anyone has any tips to offer, please let me know before I take on this project. I haven't yet searched this site...I'm sure there are probably posts available.

Ian, that would be nice if they're the same as my guess is the Merc parts are less expensive and probably easier to find.

Buckda posted 04-08-2004 01:37 PM ET (US)     Profile for Buckda  Send Email to Buckda     
One note of advice:

Go back to your dealer and get a shop manual or repair manual for your engine.

Shop manuals are hard to come by and expensive, but they are more comprehensive and a good reference to have - especially if you're working on your engine yourself and mechanically inclined.

A repair manual (from a publisher such as Clymers) will also detail this sort of repair, however they are less comprehensive...but again, if you're mechanically inclined, they should do.

A Clymer's brand manual should cost approximately 25 bucks, but if you do a lot of work, over the years, it will prove itself well worth the sacrifice of substituting a week of Starbucks coffee in the morning with a home-brew.

Good luck.


Legobusier posted 04-08-2004 01:55 PM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Dave, I do have the Clymers manual already. It's decent. I'm sure it's not as good as the "official" Honda manual, but has what looks like pretty good instructions and diagrams.

Like I said, I'm pretty mechanically inclined so I hope I can handle it. I was feeling better about it before reading this post from Jim....

Hopefully I won't have the same result. Also, my local Honda dealer had all the parts in stock, so I guess I've got an albatros dealer or I just got lucky. I even asked him when he could get to it if I wanted to have it done. First of next week was his answer. (For the record, this place doesn't look like the "Maytag repair shop" with guys sitting around doing nothing. The yard is jammed with boats and everyone looked plenty busy.)

Wish me luck.

Bigshot posted 04-08-2004 03:31 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
If it is a seal it is NOT a job for the DIY. Water pump is easy but if seal below is bad you will just have to remove it again. I highly doubt driveshaft seal though being it leaks in the tilted position. Oil is NOT under pressure and hence it could NOT leak from that seal being if you tilt a brick shaped item, you would see that the oil is not under that seal when tilted. There are three seals on lower units. The first being the prop shaft which is not the problem. The second being the driveshaft which I highly doubt. The third being the SHIFT shaft which would make the most sense. When tilted in that manor. This is the only seal that is usually easy to replpace. BEFORE I DID ANYTHING I would remove the lower unit and take it to ANY shop and have them pressure test it. This will show EXACTLY where your leak is, if you have one. Blue fluid would be Mercury synthetic (high perormance) lower unit oil.
SS17 posted 04-08-2004 03:43 PM ET (US)     Profile for SS17    

Actually, lower units do have pressure on them when they sit in the sun all day long. But you are right, the pressure is probably forcing out at the shift or drive shaft seal, but he'll be able to tell when he takes off the WP.

The question is what would make a top seal leak? Often it is because a prop shaft seal has failed, or been damaged. How's that? If the prop seal gets damaged, water goes in and displaces the oil out the top, or in this case possibly added more volume that caused oil to be forced out when it warmed in the sun.

Legobusier posted 04-08-2004 03:46 PM ET (US)     Profile for Legobusier  Send Email to Legobusier     
I think I will do just that Bigshot. I don't want to get in over my head here. At least that will tell me where the problem is (assuming I do indeed have one.)

Thanks for the suggestions all. I'll post a follow up in the CORRECT forum and let you all know what it was.


jimh posted 04-08-2004 04:11 PM ET (US)     Profile for jimh  Send Email to jimh     
Good point on the shift-shaft.

I was wondering if perhaps the leak might be from the lower unit being filled to the very brim, perhaps on a cold day, and then sitting in the sun on a very warm day. That might force some fluid past a seal.

Advice to drain the lower unit and check for water contamination is good counsel, too. If fluid is getting out then water can be getting in as well.

jimh posted 04-08-2004 08:45 PM ET (US)     Profile for jimh  Send Email to jimh     
[Moved thread from another forum.]

Since you mention the leak occurs when the unit is in the full-up orientation. this may be sufficiently close to horizontal that the leak could occur from either the shift seal or the main shaft seal. It would depend on how far it can be tilted, and this varies among different motors.

The main shaft seal has to function as the shaft rotates at several thousand RPM, so it might be more likely to be a source. The shift shaft does not move very much or very often.

Please follow up as I think we will all be interested to learn about this problem with your late-model Honda outboard motor.

Legobusier posted 04-08-2004 09:31 PM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Hi all, here's the latest update, and some more info.

I read some more in my Clymer's manual and it suggests doing basically what Ian suggested - draining a small amount of fluid from the drain plug and looking for water or "milky or foamy" fluid as the manual says. When I got home I did just water or anything at all unusual. In fact, the fluid still looks brand new. Bright, clean blue. The shop did replace the fluids on this engine before I bought it (about a month ago) so it is pretty new.

Engine has been in the down position (thanks for that clarification jim) for the last day. No fluid leak.

Also, I checked the lower unit fluid level and it's still full, so if it IS leaking, it is minor. I'm starting to wonder if it is some overspill or expansion issue.

Jim's idea that this may be a temperature related issue may hold some weight since both times I've noticed this have been on warmer days, but the boat was serviced in South FL, and it's only been up to the mid 70's here - it was much warmer there.

I don't know guys...guess I'm scratching my head. I called about getting a pressure test on it and can have it done pretty much any time for about $70 at the Honda dealer. I imagine I can get it done elsewhere cheaper as Bigshot said - it doesn't need to be done by a Honda shop.

Any ideas or suggestions? I was relived by the appearance of the fluid and am thinking this may not be all THAT bad - at least not yet. I'm thinking I may just keep an eye on the fluid and levels for the season, then pull it this winter and put the new water pump and all in then. Is this crazy?

Thanks all for the ideas and your patience with my learning curve. I hope to repay the favor someday.

Buckda posted 04-08-2004 10:10 PM ET (US)     Profile for Buckda  Send Email to Buckda     
"I'm thinking I may just keep an eye on the fluid and levels for the season, then pull it this winter and put the new water pump and all in then. Is this crazy?"

I think so. If oil is getting out, water will definitely get in, and in this case, water is the ultimate enemy. I'd solve the puzzle before running her in the drink.

Then again, I'm ultra sensitive after just having my motor rebuilt this fall/winter. Completely different problem, but anything out of the ordinary now warrants critical attention in my book.

Just my opinion...perhaps you should get a suggestion on potential problems from your mechanic as well before you decide to do it yourself, have them look at it or "let it ride" through the season.


captreils posted 04-08-2004 11:14 PM ET (US)     Profile for captreils  Send Email to captreils     
I don't think your shift shaft seal would cause your oil leak. The water pickup goes directly to the water pump and from the pump directly to the powerhead. It is a sealed passage. You can perform a pressure test fairly easily. Any kind of small hand pump will work. All it needs is a pressure gauge that reads 0-15 psi. You can pickup the proper drain plug adapter at a West Marine. You should remove the lower unit for the test and remove the water pump since the base seals are suspect. Remove gear lube and pressurize to 7 psi. Check for leaks by spraying soapy water on the seals and looking for bubbles. If no leaks go to 15 psi. Do not go past 15 psi. If no leaks it should hold at 15 psi. These are the generic steps I use when troubleshooting a lower unit. You can always refer to a service manual for specifics.
Legobusier posted 04-09-2004 06:46 AM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Are you saying perform the pressure test with the water pump & seals OFF or am I misunderstanding you? Aren't these the seals that are supposed to be watertight in the first place?
Legobusier posted 04-09-2004 07:56 AM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Pete, after looking at my Clymers manual a bit further and re-reading your post, I assume you mean remove the water pump body & impeller, but leave the base in place (which appears to hold the two seals in place). This will provide me with an unobstructed view of those seals. Am I correct here?
weekendwarrior posted 04-09-2004 03:15 PM ET (US)     Profile for weekendwarrior  Send Email to weekendwarrior     
If your Honda is like my 50HP Honda then you can remove the pump and the oil seals are still there.

Personally I would not run it at all until you have the leak fixed. Lower units are not cheap, a new seal is (relatively speaking). Your picture looks like a significant leak to me. Get it fixed now before water gets in and damages the lower unit.

LHG posted 04-09-2004 04:54 PM ET (US)     Profile for LHG    
First of all, the Honda 75 and 90's use Mercury 4 1/4" lower units. Honda buys them from Mercury, so if necessary, any Mercury dealer can easily service those lower units.

Since you've got gear oil leaking out of the WATER intakes, you've got a problem that needs immediate attention. Consider it somewhat akin to blood running out of your mouth (your water/beer intake!) Your engine needs to see a doctor!

captreils posted 04-09-2004 05:04 PM ET (US)     Profile for captreils  Send Email to captreils     
What I meant was to remove the water pump housing, the impeller, and the wear plate, so you can see the seals. The way yours is leaking you may be able to see the bad seal without a pressure test.
Legobusier posted 04-09-2004 09:07 PM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Thanks guys. I'm going to try to pull it this weekend if I have time & will let everyone know what I find.
Legobusier posted 04-10-2004 10:35 PM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Hey guys...time for an update:

I drained the lower unit tonight and pulled it. Lube looks good - nice and clean. I captured it and put it in a glass jar & will let it settle and inspect it again in the morning, but I don't expect to see anything unusual.

Pulled the lower unit. It was really easy. Took me about 20 minutes. Having never done it before, I was a bit worried, but everything came right off clean and without issue.

Pulled the water pump - also very easy - about 10 minutes. I was happy to see the condition of the water pump. It looks brand new & is still nice and soft with no cracks, etc. The wear plate shows very little wear as well. I suspect it was changed within the last few months.

I went to Home Depot and got everything I needed to build a pressure tester. I used a gas line test meter - has a gauge and "bicycle like" air fitting. A few brass fittings and some hose and I was all set. Cost about $20.

Pressure tested the unit to 14.5# per my manual (using a bicycle pump) and guess passed. I let it sit for over an hour under pressure, turned the shafts, etc. with no loss of pressure. Being the skeptic that I am (and given that I seem to have an issue here), I submerged it while under pressure - it sat in the tank for an hour or so.....still no leaks.

Soooooooo, I'm not sure where this leave me. I guess the mystery continues. In one sense I'm certainly happy I don't appear to have a serious problem, but on the other hand I sure would feel better if I knew where the supposed leak was coming from.

Anybody have any suggestions as to what to do now? Iím thinking Iím just gonna put it back together and keep a close eye on it. Please speak up if you guys think of something else for me to look at.

Thanks again,

Chuck Tribolet posted 04-10-2004 11:03 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Try testing it at lower pressure, say 3 psi.

A common problem is underwater photography is that the
camera housing leaks at one or two feet, but not deeper,
because the greater pressure crams the o-rings into place.


jimh posted 04-10-2004 11:45 PM ET (US)     Profile for jimh  Send Email to jimh     
Chris--I would love to hear more details of your pressure testing unit assembled from commonly available parts. This could be very useful on a boat in a number of situations, including the one you just described and perhaps testing of fuel tanks.

Please give consideration to starting a new thread with a topic of something like "Home Brew Pressure Tester". I think it would be a great source of information!

Legobusier posted 04-11-2004 10:44 AM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Per Chuck's suggestion, I attempted a low pressure test this am and (drumroll please) it failed. I could hear air escaping around the seals at the base of the water pump. If I wiggled the drive shaft slightly, I could get it to seal, but I obviously found the souce of the problem. Sounds like these seals are not easily replaced by the DIY'er according to Bigshot - also the manual makes it look pretty involved, so I guess I'll take it to the shop unless I hear from one of you that it's not that bad.

Jim, I will follow up tonight on the pressure tester post.

Thanks again,

Legobusier posted 04-11-2004 08:58 PM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Perhaps it the countless number of hours I spent with my dad tearing up engines and stuff while I was growing up, or it may be that I'm impatient, but I decided not to take the lower unit to the shop.

I read the manual a bit more closely and there are some engines (remem this book is pretty much for EVERY Honda engine) that requires you to completely disassemble the lower end to pull the seals, so that's where my apprehension came from; however this is not one of those models. On this model, the seals are just underneath the water pump base and seemed to be easily accessible, so I decided to try it myself.

I pulled the base off (6 bolts) and pried it off and could immediately see the problem. The top seal has a spring like washer that is held in place by a rubber bushing. The spring thingie had a little "kink" in it - obviously not making a good seal. It popped out of the base easily enough with a small screwdriver. The bottom seal looked like it was fine - no apparent signs of wear. Popped it out and cleaned up the base plate.

I went to install the new seals and discovered that the new bottom seal is the wrong size. I think they just gave me the wrong one (it's not even close), so I'll go get the correct one tomorrow and see where things go, but I really don't anticipate any problems. I may have to "press" the seals very slightly with a pipe to install them, but it should be pretty easy.

Looks like Jim was right on with his prediction.
I'll keep you guys posted.


Legobusier posted 04-15-2004 10:32 PM ET (US)     Profile for Legobusier  Send Email to Legobusier     
Hi all,

Just wanted to give everyone the final update (I hope) on this procedure. I FINALLY got the correct seals today. I spent an at my Honda dealer Monday with the seals and base plate in hand with him trying to figure out what was up. He pulled up the number on the computer 15 different ways - same number. Seal OBVIOUSLY doesn't fit - it's about a 1/4" larger diameter. He called his Honda parts rep & that guy looked at it 16 different ways with the same result. Everyone scratching their heads. He pulled out a new base plate (with seals intact) and it had basically the same seals I had - but with some additional collars. Finally, he said he would get to the bottom of it and I left. The only thing they could figure was that Honda had packaged the wrong seals in the envelopes (or tagged them wrong), so they had new parts FedEx'ed to them.

Just came in today and they are correct, so apparently they discovered a problem in their system somewhere. To complicate things further, Honda did a mid-year change - guess what model year...'98.

Anyhow, got home and popped them in. They go in pretty easy. I followed up with a low pressure (thanks Chuck) pressure test and it held just fine. After dinner I went out and put on the new water pump and re-installed the lower unit. Lubed it up and I think I'm back in business.

Thanks for all the suggestions and support on this project. I've learned a lot about the boat, and even a little about myself. I've also learned the Clymer's manuals are worthless if you're a novice. I have done enough of this type of work to realize pretty quick to just use it as a guideline, but certainly NOT a step-by-step guide.


Phil Washburn posted 09-17-2009 04:16 PM ET (US)     Profile for Phil Washburn  Send Email to Phil Washburn     
Someone here in this string mentioned lower units on some Hondas are mercury!!!is that correct? this is very good info if correct. I have a '99 30 hp (BF30A I believe) and need a replacement lower unit (my case is cracked) and I can't find a used one anywhere. Could anyone comment on this, and is there anyone who might know where one is? Is a midsize Merc lower unit the same (30-50hp)????
Just a side note on these Hondas. This 30hp is my first outboard Honda I've owned, and I initially thought Honda was the best there is, but to find parts, new or used or to find a mechanic who works on one in my area is a real pain. It's like looking for foreign car parts in the '70s, people look at you like you have two heads.

thx a bunch

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