'79 9.9HP Exhaust Relief ports holding water

Engine is a 1979 Evinrude 9.9HP Model# 10924B.

I've noticed the relief ports in the midsection seem to be holding water. If I let the engine set vertical after running it seems to drain all the water out, but if I take the engine off the boat and set it on the ground with the prop and back of the engine facing down there will be a good bit of water drain out the exhaust relief ports.

The engine runs just fine and when the thermostat opens I get a mixture of exhaust and water coming out the relief ports. By all accounts everything seems to be working properly.

This engine should be completely self draining so I didn't think any water would be held in the mid section. My guess is there is some kind of blockage but I'm not sure where to look. I would appreciate any suggestions of where to look so I can get the engine completely draining of all water after use.

Thanks.

As I understand your post, you could be using your 9.9 for a days outing and encounter no problems, return home and park your rig in the driveway for example... and let it sit there with the engine in a normal upright running position for at least a half hour or so, in which time the water within should drain out completely but for whatever amount usually left to evaporate.

Then, after a hour or so... you remove the 9.9 from the boat and lay it down as one would normally do... the prop and rear portion of the hood touching the ground... and water, as I understand it, pours out of the two exhaust relief holes?

How much water?.... A few small puddles resulting from dripping wouldn't worry me... BUT, say a pint of water suddenly flowing out certainly would. Personally, in my 30+ years in the field, I've never encountered that problem. If indeed a pint of water, that amount could lead to big problems if in a area that encounters freezing weather.

At the moment, I can only suggest that you check all of the small drain holes in the lower unit as should even one be clogged... that could trap a considerable amount of water that could back up to that area when horizontal.

The long exhaust housing, between the powerhead and the lower unit contains a inner exhaust tube... between that tube and the outer housing, it fills with water, needed to prevent all the paint burning off of the outer housing, I don't recall just how that water drains out but I'm sure another member here will advise you on that... another area to check but unfortunately removing the lower unit would be necessary.

My guess is one or more drain holes in lower unit are blocked.

That is the exact situation Joe. Maybe not a pint but maybe a cup or so worth of water and you're exactly right, my concern is in freezing weather and potential damage to the housing.

Which drain holes should I be looking to find? Are the drain holes circled in this picture the ones that I should be looking to clear? Do you guys think I need to pull the lower unit to probe drain holes or should I be able to do this with the LU attached? I'm good either way since it's only about 15 minutes of work to remove the LU.

I apologize for my ignorance, but I guess I've never really paid attention to the cooling passages in the LU to really know what's happening. I fought cooling issues on this engine when I first got it a few years ago (power head grommet at water tube inlet) and those have all been solved. Maybe the draining issue has always been there too and I didn't notice it before, but last fall when I winterized the engine I laid it down off the stand and saw the water run out the relief holes and I started wondering what was happening.

Thanks for the help.

Kevin.... No, those holes are actually a thermostat outlet. Normally no water would be seen coming out there until the thermostat opens... seen only while running on a flushette of course. If you manage to ever clog those holes, I'd want somebody to tell me about it!

The drain holes are scattered around the lower unit, guessing a size of about 1/8", possibly a little smaller in diameter... such as you can see pictured above in the forward portion of the gearcase just above the inner workings case bulge, looks like a small dot in the graphic. There should be several so look closely.

This picture From Leeroys ramblings show a drain hole from a lower unit cavity



Look also for drain holes along the joint between the LU and the exhaust housing like the one ringed below. ( Ignore what the pencil is pointing to. This is a Yachtwin and that's the exhaust outlet)

Thanks guys. I know which holes you're talking about, I just didn't associate those with draining of the mid-section and lower unit. I'm on board with you now. Come to think of it, when I pull the boat out of the water I don't recall see much water (if any) come out of those holes so I bet there's some trash in those passages causing my problem.

This engine had a very unknown history when I bought it so who knows how it was ran (or through what) before it came into my possession. When i was chasing down my cooling problems I did find bits of rubber wedged on the thermostat so it's entirely possible a previous owner shredded a water pump impeller. I'm guessing I'll find rubber and mud packed into those drain passages. It should be quite an interesting adventure.

kevinj said:

It should be quite an interesting adventure.

Click to expand...

And an easier one than what you already went through with the water tube grommet, since it should (fingers crossed) be contained in the L.U.
Good luck, looking forward to the updates!

kevinj said:

Thanks guys. I know which holes you're talking about, I just didn't associate those with draining of the mid-section and lower unit. I'm on board with you now. Come to think of it, when I pull the boat out of the water I don't recall see much water (if any) come out of those holes so I bet there's some trash in those passages causing my problem.

Click to expand...

When I purchased my '76 15hp a couple of years ago, I got it home after barrel testing it at the sellers and I dropped the LU about a day or so later to change the impeller. The cavity that, that hole is draining was 3/4 full of water, it was draining VERY slowly. Mine was a fresh water motor and it was an easy clean. Hopefully the same will go for yours.

Mine is fresh water too so it should be easy. I’m betting I’ll find bits of impeller. I’m hoping I get time this evening to work on it.

I see those cavities / drain holes packed with sand and silt.-----Have used a drill with wire to clean them out.

kevinj said:

Are the drain holes circled in this picture the ones that I should be looking to clear?

View attachment 19775

Click to expand...

Funny you brought this up. When putting mine away in the fall, I noticed a circular piece of rubber in there.
As soon as the weather gets warmer here I'll be dropping the LU to checkout what it is...

racerone said:

I see those cavities / drain holes packed with sand and silt.-----Have used a drill with wire to clean them out.

Click to expand...

Exactly... IIRC I used a piece of copper wire and the hose to clear mine out.

racerone said:

I see those cavities / drain holes packed with sand and silt.-----Have used a drill with wire to clean them out.

Click to expand...

Good to know. My plan was a piece of wire and compressed air. Chucking the wire into a drill sounds like a great idea....at least at low speed.

I got the LU removed this evening and did find a little gunk down in the shift linkage area that might have been blocking the drain hole on the front of the LU. That's all cleaned out but I didn't find anything on the exhaust relief side that was blocked. I did find the o-ring on top of the water pump was badly deformed. I don't know what I could have done when I installed the pump but the o-ring was definitely not seated properly. I'm not sure if that has anything to do with the issue but I don't see anything else that could be the problem. I measured the o-ring and it should be 1 1/8" ID and a thickness of 3/16". I'm going to get a replacement o-ring at my local hardware store and put it back together tomorrow.

That "O" Ring is designed to keep water from shooting up the driveshaft tube... keep it away from the lower main bearing area... just a coincidence, nothing to do with your original post. Let us know if you have a repeat of the problem.

joereeves said:

That "O" Ring is designed to keep water from shooting up the driveshaft tube... keep it away from the lower main bearing area... just a coincidence, nothing to do with your original post. Let us know if you have a repeat of the problem.

Click to expand...

I thought that might be the function of the o-ring and therefore nothing to do with my issue. I plan to reassemble everything tonight and hopefully give it another run sometime next week.