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I have a B28 with Mercruiser 260's. They have about 1700 hours on them. Run fine with no problems other than leaving a small oil slick on the water at idle. Both engines have the problem. I have read about Oil Stop Leak. Has anybody had experience with these products. I guess they are designed to help swell old seals. Haven't tried the stuff. Just curious if they work.

could be wear...rings..try some thicker oil..
Wayne

It could be your engine oil coolers or gear oil coolers (if you have them). I'm not sure how worn rings get you a slick, or really bad seals. Worn rings should get you blue smoke, and if they're that bad, you may not get max. rpms. Leaking seals should get you oil in the bilge under the motors. Do a compression test if you think the motors are worn, and put white oil-absorb diapers under the motors if you think they're leaking. Maybe raw fuel from a bad carb?

Oh they're perfect, except they leak oil in the water? Are you serious? Get the damn thing out of our water! Better yet give me your Reg# and I'll have the EPA and CG help you out.

Ridiculous!

Thank you for suggesting I quantify the problem. Its about the same as an old 2 stroke outboard. Thanks

There's no oil slick behind my 1980 Johnson. Is that old enough to qualify?

Seriously, there is nothing wrong with your engines, you just need to add a dishwashing soap dispenser to your stern. Everybody knows that dish soap will make that oil "disappear".

CamB25 wrote:Everybody knows that dish soap will make that oil "disappear".

Everybody except those idiots who 'cleaned' up the Gulf after BP........

How do you know for sure it is oil? Is raw oil or a sheen/slick like when the fuel tank vent overflows.

If you have some bad valve seals, when you first start the engine it would likely smoke blue quite a bit. I do not know if it would leave a slick in the water per say.

Have you checked the plugs? Are they black from running rich? It might be excess fuel not getting burnt in the combustion process.

If you have raw oil coming out the exhaust and have to add oil to the engines frequently the aforementioned oil coolers would be suspect.

I am not a mechanic though. Just trying to help isolate the issue.

I also run a B28 with 260's. Occasionally, I'll notice a little at idle in the slip but I am quite certain mine is fuel. I don't burn any oil per se. Do you notice that you go through any oil? Do you have to top it off during the season? Wondering if unburnt fuel....

I have had very little oil consumption. The description of a sheen like the overflow of gas fill is a good description. sounds like I better have a good carb mechanic take a look.

Thanks for all the feedback.

jrwolfe wrote:I have had very little oil consumption. The description of a sheen like the overflow of gas fill is a good description. sounds like I better have a good carb mechanic take a look.

I'm not much of a gas mechanic (my forte is diesels) but a rainbow colored shine behind you could only stem from two possible engine related sources:

1) Fuel
2) Oil (either engine or gear oil)

Under certain conditions with certain steering system (which aren't applicable to your boat) power steering could be another source.

Indeed, if you have hydraulic tabs they could also be the source.

Regardless, the sooner you fix this the better for the environment!

Probably oil or fuel coolers if you have them installed. Depending how old they are, you might just want to change them out. You can also get them pressure tested, but that requires you to remove them, and since that is pretty labor intensive depending on accessibility, you might as well replace them since you have them out anyway. Hopefully you don't have a Mercruiser 3 in 1 heat exchanger/oil cooler/transmission cooler like in my 1995 Mercruiser 7.4 EFI MPs. One of my oil coolers failed and I had to re-engineer my whole cooling system with custom made heat exchangers and off the shelf oil and transmission coolers. My personal experience with a transmission cooler failure on a Borg Warner transmission that uses Dexron Mercon automatic transmission fluid is that if the transmission cooler fails, your tranny fluid will look like Pepto Bismol. The oil and transmission coolers are just over $100 each. If you can't buy them locally, check online with "Mr. Cool" for a wide selection.

I have a set of 260's in my 28 with 1300 hours. I get a little bit of sheen, mainly after start-up. Mine is just fuel from the old - tech Rochester carbs. Never use any oil or trans fluid, so i think my coolers are fine.