Too much Seafoam in motor oil ?

[tpenfield]

OK, I went to change the oil on the Mercruiser 7.4's this weekend, and had some extra Seafoam. So, I added a can (16 oz) to each engine before the oil change and ran them through a 30 minute warmup, then pumped out the oil.

To my surprise the oil came out foamy. So, initial thought was "oh great freeze damage".

My engines are both full closed cooling running a 50% AF mix, so I was thinking that they should not have frozen ( lowest temp was around 10F this past winter)

The cooling systems both hold pressure, so I am thinking that a whole can of Seafoam, being about 50% more than recommended was way too much for a flush. . . Or . . . I had the oil level too high and it may have been up to the level of the crankshaft .

I completed the oil change and ran each engine for 10 mins and the new oil has stayed clear.

Thoughts?

 

[Bt Doctur]

If you ever want to add anything to a motor, just use Marvel Mystery Oil

 

[GA_Boater]

What was the name of the stuff you put in? SeaFOAM LOL

I'll guess half a quart thinned the oil causing the foaming. Did you check the oil level before adding?

 

[tpenfield]

What was the name of the stuff you put in? SeaFOAM LOL

I'll guess half a quart thinned the oil causing the foaming. Did you check the oil level before adding?

Yea the level was a bit high, so that it what I was wondering if I made it too high. Time will tell . . . if the new oil gets foamy/milky, then I know I have a problem. I am just hoping that the fact that both cooling systems held pressure for an extended amount of time (hour), it would be a positive sign.

I was worried that my antifreeze (green stuff) was too weak or something. . . I checked the core plugs and looked for any signs of cracks, etc . . . nada. Also no water coming from the bilge during my test runs, etc.

 

[tpenfield]

Quick update . . .

I have been doing a bit of detective work to figure out why/how the oil got to looking foamy/milky.

I heated some of the old oil and there was some water in it, as it boiled off . . . so probably more an issue of water than of the seafoam So, I was wondering where the water would have come from . . . oh yea, I did a water decarb in November right before winter layup.

So, my theory at this point is that the decarb with water resulted in some water getting into the oil. . . hard to say how much as the oil did not look as milky as some of the pictures that we typically see of water/oil mishaps. I had not read anything that talked about or warned about water getting into the oil while doing a decarb, but I guess it is possible. Also, as I recall the oil level, although a bit high did not look milky before adding the seafoam.

Of course, I did not change the oil until the spring prep :facepalm: so probably nothing good happened while it sat over the winter. I did do the MPI fogging of the engines before layup, so the top-end was good and soaked with oil.

Anyway, The engines seem to run fine . . . very smooth and good power (4400 RPM @ WOT) which is as good as they ever have run.

Wondering if I should do a mid-season oil change or something . . . maybe a compression test . . . or just see how things go this season and run a full battery of tests this coming Fall before layup (and change the oil) :noidea:

 

[alldodge]

Wondering if I should do a mid-season oil change or something . . . maybe a compression test . . . or just see how things go this season and run a full battery of tests this coming Fall before layup (and change the oil) :noidea:

Opinion: You running better then you have in some time, engines are telling me there are no issues. Run have fun and winterize in the fall. Leave the snake oil in the store

 

[tpenfield]

Opinion: You running better then you have in some time, engines are telling me there are no issues. Run have fun and winterize in the fall. Leave the snake oil in the store

Thanks, AD. I have run the engines for about 3 hours cruising so far . . . mostly around 3K RPM, with a WOT test yesterday that got up to spec and where it was when I bought the boat. The oil has stayed clear and temp & pressure are normal. So, I'll assume all is good until it decides otherwise.

840 hours on the engines now . . . so I have put 100 hours on in 2 seasons.