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TOPIC: Source of oil and water in combustion chamber

Source of oil and water in combustion chamber 2 years 3 months ago #123678

  • dspeck
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I need some help in diagnosing a problem with my 1961 Evinrude Starflite III 75 HP which I bought along with with my 1960 center deck G3. This post will be a little long, but I want to share what has happened and what I did before I ask my question. I am not a mechanic, but I do love tinkering. So, please bear with me.

The motor was running fine a week ago until the gas supply line broke just below the carburator intake nipple at the top of the carb. I also had a shifting problem that required replacing the "exhaust housing shaft and arm." So, I decided to fix both problems at the same time. Prior to this event, I had removed the lower unit only once and that was to paint it. After the paint job reassembly, the engine ran well with no apparent problems.

Replacing the shaft and arm assembly required separating the exhaust tube from the power head which was easy to do. This, in turn, required replacing both the "adapter to outer exhaust tube gasket" and the "adapter to power head gasket." I made these replacements without any problems I could see. And, since I had it apart, I also replaced the "inner to outer exhaust tube gasket." Following these repairs, I reassembled the exhaust tube to the power head, remounted the head/exhaust tube to the swivel bracket and exhaust covers, and remounted the lower unit with a new gasket between the lower unit and the exhaust tube. Maneuvering the cooling tubes and aligning the shift linkage was tricky as usual, but, with patience, accomplished.

My problem began when I tried to restart the engine. I had trouble getting it to fire and when I did it ran very roughly for a short period. Then, the the fuel level began to drop in the sediment bowl and the engine would starve and die. I got it to restart several times, but it became increasingly difficult to crank. I pulled the plugs and tried to crank it by hand and could barely get it to move. Since I was was using a contemporary 2 cycle oil at a 16:1 ratio, I feared it may not be getting sufficient lube. I shot fogging oil into the cylinders and cranked it by hand until it loosened up and would spin easily. I reinstalled the plugs and tried it again and it started right up but still was rough and again starved out (several times.) I then pulled the carb and broke it down to make sure it was clean and replaced the float because I happened to have a new one that was noticeably lighter than the existing one. I reinstalled the carb and tried again with the same result only this time, I started to get an oily, scummy, whipped cream like discharge from the lower unit water discharge vent. And, it was getting hard to crank again. I pulled the plugs again and this time the threads and the tips showed the same scummy stuff and little droplets of water. I checked the lower unit lube and it was full but creamy in color. I pulled the lower unit and found it and the exhaust tube coated in the same creamy substance that was discharging from the the lower unit exhaust vent.

That's the background. Now the question/s.

I concluded that the lower unit lube and cooling water barrier had been breached and that gunk had made its way into the power head. But, I can't figure out how. I did discover that the hot water discharge tube grommet was missing but I don't know if it was ever there or not. So, here's my questions.

1. Is the hot water discharge tube grommet integral to holding the lower unit lube in the gear housing?

2. The only "seal" the parts diagram shows between the gear housing and the rest of the lower unit is an "O-ring." Is that what keeps the lube out of the exhaust tube?

3. How can cooling water and lube get into the power head? I know a blown head gasket could account for the water, but not for the water being mixed with lube. The only explanation I can come up with is that it was somehow forced back up through the inner exhaust tube because that's the only open pathway from the the main exhaust tube to the power head.

I realize this is a lot of text, but I hope it helps those out there who know way more than I do to offer some insight. It will be MUCH appreciated.

Doug

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Re:Source of oil and water in combustion chamber 2 years 3 months ago #123693

The gearcase is a sealed unit, its lube isn't going up top.

I believe your motor has the t-stat outlet that recirculates water until the t-stat opens. Do you have 2 water tubes going to the top of your water pump? If so, I suspect you have them reversed & the water is flowing backwards thru he power head thus getting into the cylinders thru the exhaust cover.

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Re:Source of oil and water in combustion chamber 2 years 3 months ago #123735

  • dspeck
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That certainly explains the symptoms. I thought I had reassembled it the same way I did the other time I removed the lower unit, but the fact is I didn't see the position of the pipes as I withdrew the lower from the exhaust tube. I read the parts diagram more closely and can see that I have the intake tube in the exhaust port. Thanks for such a quick response, Jim.

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