5.7 Mercruiser 350 Oil Leak

maxse

Member
Apr 16, 2017
108
New York, NY
Boat Info
260 Sundancer 2007
Engines
Single Mercury Stern Drive 300HP Bravo III
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Here is where it’s leaking right at the fitting. Any ideas? Is it probably just the connector or something bigger?
 
The picture is the oil pan drain plug/hose and when I feel around it seems like the threads are tight but the hose freely moves around and feels like there is some play slightly up and down. Is it normal for that drain hose to move around?
 
Drain the oil, or suck it out with a pump. Take that fitting out throw it away... Put a reg drain plug it in change the filter and fill it back up with fresh oil...
 
I don’t have to drain it because it drained itself, all over the Bilge unfortunately :)

I’ll replace that for sure no idea why it was even like that as I’m pretty sure the mechanics use an extractor. I’m just hoping the issue isn’t the pan itself with corrosion. If it is I’m sure it’s a big job.
 
I installed two new engines and they came with those hoses, I didn't use either one. They would not have worked in my boat for one thing, also, they look like a failure point to me. I kept it simple and left the plugs in and use an extractor pump. I'll bet yours is leaking at the swivel, the weak point of those hose connections.
Pull it and install a plug, change your oil and filter and clean your bilge and go boating.
 
Thanks Guys! I’ll update the thread here once everything is set.
 
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It was the pan...Shop says about 10 hours and they are starting right away will have it done in a few days hopefully.
 
I had the identical issue with our '06 260DA. OEM oil pan and gasket-$350, labor to pull the engine and replace-$900.

That was 3-4 years ago.

Bennett
 
I wonder if you can buy some time with a temporary repair so you won't have to loose time and money in the middle of boating season....

I have no experience with this stuff but their claims are impressive....maybe you can clean the oil off of the pan and install a plug the best you can and try a few coats of this tuff to see if it will work....

cliff

shopping
 
I think the flex seal and even jb weld have a good chance of stopping the leak. The question is for how long...

I would probably try it in a desperate situation where I would lose a week or more but since my shop was able to get it done in 2-3 days I’m willing to lose a few days to get it done right and not have to worry about it.

I was planning on trying something like this as I expected the shop to say 2-3 weeks.
 
So I guess this begs the question....why is the pan rusty? Have you had water sitting in the bilge?
 
So I guess this begs the question....why is the pan rusty? Have you had water sitting in the bilge?

Last summer we went 3 weeks without checking the bilge and of course the float switch broke. I check it religiously now but I’m guessing that didn’t help...Also it’s 10 years old.

I installed a new rule pump with a johnson float switch after researching different options. I would like to have one of the “automatic” pumps to keep the bilge as dry as possible but have heard they burn out easy.
 
In my situation, I initially noticed a very small amount of oil in the bilge water. Over about a month, it increased, but never had to add engine oil until one day, we were out, and I decided to get in the bilge and continue looking. When I opened the bilge, there was a quart or two of oil in the bilge. Checked, added, slowly but deliberately made our way to the nearest marina. Bought a couple gallons of oil and headed to the ramp with eyes glued to the oil pressure gauge. Made the run and put her on the trailer. Cleaned it all up and out and figured out that the oil pan had been patched in the past with something resembling marine Tex. Cleaned it off good, mixed up some more marine Tex and smeared it all over the bottom. Just could not stop all of the pinholes. Took it in and got it back 10 days later. My pan looked identical to the one pictured. Inside was as pretty as a new one, but there were a good number of holes, some the size of a ball point pen end and some true pin holes.

Bennett
 
Sorry I don't agree with the 10 year old statement. I have a 33 year-old boat with a 15 year-old motor. Still has the original oil pan. But I do understand about the float switch quitting. That happens so often that I quit using them. I now use these....
101series.jpg

This is a Water Witch. They are $40-$50 and available on line. https://waterwitchinc.com/product/model-101-bilge-switch/ They work via conductivity caused by bilge water making a connection between the tab on the bottom and the round disk higher on the body of the switch. there are no moving parts and no adjustments. There is a 6-9 second "On" delay and a 14-16 second "Off" delay. this prevents rapid cycling. I had 4 of these on my 52' Motoryacht and they did not fail. In fact this model has a 5-year warranty.
 
Sorry I don't agree with the 10 year old statement. I have a 33 year-old boat with a 15 year-old motor. Still has the original oil pan. But I do understand about the float switch quitting. That happens so often that I quit using them. I now use these....
View attachment 57461
This is a Water Witch. They are $40-$50 and available on line. https://waterwitchinc.com/product/model-101-bilge-switch/ They work via conductivity caused by bilge water making a connection between the tab on the bottom and the round disk higher on the body of the switch. there are no moving parts and no adjustments. There is a 6-9 second "On" delay and a 14-16 second "Off" delay. this prevents rapid cycling. I had 4 of these on my 52' Motoryacht and they did not fail. In fact this model has a 5-year warranty.


+1.....I replaced my bilge pump a couple years ago and used the 'water witch' switch instead of a standard float switch....

cliff
 
I'll definitely be getting one of these then. @CliffA How did you make out with the wiring since the water witch needs constant +12V? The way my helm switch is wired it's just on/off as an override with the off being "auto" I guess...

@NorCal Boater Maybe I am totally off here but maybe this is a more common problem in smaller boats since the engine room is so compact. My oil pan sits only a few inches from the bilge floor. I almost wonder if the float switch would kick on before the water makes it up to the first 1/2" of the oil pan which is exactly where mine is rusted...
 

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