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Author Topic:   Evinrude 225 lower unit joint
kingfish posted 08-28-2001 09:30 PM ET (US)   Profile for kingfish   Send Email to kingfish  
I have been noticing for a while, and with just having run a dose of de-carbon tune-up juice through the priming circuit today I have noticed a lot more, that the joint in the lower unit that separates to access the impellor, leaks. The signs that have been apparent for a while are minor traces of oil or exhaust residue showing up on the white paint right along parts of the joint.

Today, after giving the motor a dose of de-carboning spray through the priming circuit (similar to fogging in the fall, only different stuff)and letting it "soak" over night as per instructions, I started the motor back up and ran it at fast idle for 15 or 20 minutes with earmuffs and exhaust muffler in the driveway, to blow out any loosened crud. I climbed out of the boat while the engine was running and went back to look at the joint in question, and could clearly see water actively running out of the joint on both sides, and dramatic black staining below the joint from the de-carboning or exhaust or both.

I didn't put a torque wrench to the bolts, but I did put a wrench to them and took a good strain. I don't think a torque wrench would show much if any tightening was indicated, judging by the little bit I could get the bolts to turn.

Is there a gasket at this joint that goes bad from time to time? Is it simply a pressed joint? Should I be particularly concerned about what I have described?



Kelly posted 08-28-2001 09:39 PM ET (US)     Profile for Kelly  Send Email to Kelly     
I am anxious to see the responses cause I am experienecing the same condition. Kelly
DIVE 1 posted 08-28-2001 10:01 PM ET (US)     Profile for DIVE 1    
Look at the parts diagram for your motors and see if they have inner exhaust housings. There are rubber seals at the joints of the inner exhaust housings. If they are bad, this may be causing your problem.
lhg posted 08-28-2001 10:46 PM ET (US)     Profile for lhg    
JCF: Just to be sure, have checked the gearcase oil for presence of water? If none, I would at least guess that the problem couldn't be too serious, and is a lower unit seal gasket of some kind.

I think there is previous forum discussion on
pulling the lower unit to replace impeller, so there may be notes on the accompanying gaskets also. I would imagine most brands of engines are similar in this regard. I'll take a look at my Mercury repair manual and see how Merc does it. Never have done an impeller replacement myself, but I have seen the new gasket kits that seem to go along with the job.

Tom W Clark posted 08-29-2001 01:10 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
I don't think there is any gasket at that joint. It is a metal to metal joint on the other (non 225 hp) Johnson outboards I've owned. Exhaust leakage at the joint is not uncommon nor indicative of anything bad, it just makes a mess.

I have put Permatex on this joint on a couple of my motors and this will solve the problem, at least until the aluminum corrodes a little more and opens up a new avenue for the exhaust to escape.

Airborne posted 08-29-2001 04:49 AM ET (US)     Profile for Airborne  Send Email to Airborne     
Yes, there are two gaskets on your exhaust housing. Pull off your lower unit and you will see one of the gaskets inside the mid section. you can pull out this exhaust extention and inspect the upper gasket. Just give it a good yank. It may just be kinked. The exhaust residue is not bad for you motor but it looks bad and is a pain to clean.
sorcerer posted 08-29-2001 07:33 AM ET (US)     Profile for sorcerer    

Might add to Airborne commitment, which is correct, if you pull the lower unit you might want to:

1. do your water pump
2. clean up the edges where the upper and lower mate, use zinc chromate and then OMC Tempo paint to match.
3. then maybe you should pull a pressure and vacuum test on the lower unit to check the seals.

kingfish posted 08-29-2001 03:34 PM ET (US)     Profile for kingfish  Send Email to kingfish     
Thanks, all - and as usual, I can't help but be impressed with the expertise and willingness to share opinion and experience around here.

I am not going to have time before a mini-rendezvous over the Labor Day weekend to get into the research and tear-down, but I have been planning to change out lower gear case oil. I'll do that tonight and if there is anything seriously amiss, it should obviate itself there.


kingfish posted 06-18-2002 08:53 AM ET (US)     Profile for kingfish  Send Email to kingfish     

I bought a water pump rebuild kit over the winter and at the recommendation of a local marina, the *lower* exhaust tube gasket. Finally got around to seperating the lower unit a couple of weeks ago and found out what everything looks like in there. Lots of carbon, so I cleaned everything up well before I started. Water pump rebuild went well; old impeller, o-rings and gaskets looked OK, but went through the drill anyway. The "base plate" for the impeller (not sure of the correct terminology) showed some evidence of wear and scoring from grit of some nature that had come in with the cooling water, so I felt good about replacing it.

The *lower* exhaust tube gasket looked fine, just compressed as you would expect. The *upper* exhaust tube gasket however looked like it had been chewed by mice! It was intact, that is it was still in one piece, but it had pieces missing on two adjacent sides that gave it an appearance that I can only best describe as if a rodent had worked its way along it and chewed hunks out of it.

So I ordered an upper gasket, put everything back together (learned how to thread the shift rod into its linkage bracket), dressed up the case mating surfaces, ran a thin bead of permatex along these surfaces, bolted her up and tested the fix last weekend.

Voila!! No stains at all, and I got the impeller and its retaining key on right, because I had cooling and good pressure.

I am surmising that I was the cause of the chewed up upper gasket. I have used a propeller hub muffler I bought through Overtons when I have had the motor running on earmuffs in the back yard, so the neighbors wouldn't get into high dudgeon over the racket. I am suspecting that I ran the spring loaded screws on the muffler plate in too far and caused such back pressure that the path of least resistance was the edges of the upper gasket rather than the muffler. Only a guess, but I'm not going to use the muffler any more. And my motor isn't as loud or as frequent as the neighbors dog, anyway...

So the nest step will be taking Sorcerers advice about the paint touch-up (and will repaint thr raw metal on the lower gear case hub and skeg where somebody got into shallow water at the same time).

kingfish reporting-

David Ratusnik posted 06-20-2002 09:01 AM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
Kingfish- Your theory about the muffler causing back pressure and possibly contributing to gasket failure might be worth another post (by itself). I've outsmarted myself on a regular basis in boating and was going to invest in that muffler- now, nope. Maybe others have had similar experiences- the device was probably not reviewed by FDA or NIH before going to market. .03 David
bigz posted 06-20-2002 09:19 AM ET (US)     Profile for bigz    
Hmm JF, shallow water running is it well a sure cure for the next time that 'someone' decides to try it take Clark Roberts advice. Put a hydraulic jack plate on her!

Heck you've got everything else under the sun on that beautiful Outré might as well ad one more accessory (toy) chuckle ---


kingfish posted 06-20-2002 09:41 AM ET (US)     Profile for kingfish  Send Email to kingfish     

Thanks - I'm with you; I sometimes think that outsmarting myself is my primary self-educational agenda. I'll think about a way to develop a new thread.


It must have been my evil twin brother...

You know, with a hydraulic jack-plate, I could fill in the transom and develop the closed storage back there you and I talked about in NC...Hmmm...

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