Hi guys,

I am currently on the hunt for a new boat and an intriguing deal has come up. The boat's starboard 502 had water in the oil and the gentleman's mechanic told him it was due to a bad oil cooler. Knowing that water in oil is usually due to intake leaks, blown head gaskets, cracked blocks, and exhaust leaks, I am wondering how likely is it that the cooler is the issue?

some notes about the boat:
its a '93 formula with 502s and HP 500 intakes. It also has EMI thunder exhaust manifolds that are freshly powder coated (maybe covering up signs of corrosion)
the heads are stock but had a valve job approximately 100 hours ago
It was used occasionally in salt but was at a fresh water port so it should have been flushed.

My current thoughts are that it is more likely that the intake or exhaust is leaking (since both are aluminum) due to the increased corrosion from salt use, but I would be elated if it was just the cooler. I am just thinking that it would be far more likely that oil would be going into the cooling water and out the exhaust if the cooler was bad, not the other way around as his mechanic claims.

He also claims that all cylinders have good compression (I'll be sure to check) so that should rule out the head gasket.

Let me know what your thoughts are on this and if you think I should take a chance on this one.

Thanks,
Jake

An oil cooler is an easy fix, so the seller should just fix it unless he's giving the boat away or close to it. If it's been sitting awhile that water in the oil is very corrosive to the internals. If you're bent on getting the boat you can get some 1-1/4" copper pipe at a Home Depot to bypass the cooler and flush the oil a few times. My thought though is if it was really just the cooler and he took care of the boat he would've replaced it by now. It's relatively cheap and easy compared to cutting the value of the boat in half.

Ya that seems like an easy thing to say and if was checked for leak you'd think it woulda been replaced at the time. They obviously can spring a leak but just don't hear of that happening as much as the others you mentioned including reversion. Was it milk shake looking or more condensation look. Like above post mentioned it water in internals can really get ugly and rather quickly. To pressurize an oil cooler would be very easy to ck. In some cases if the cooler is bad the oil can leak into the water. Can depend on which has more pressure. Regardless I'd move forward with caution and for sure rule out the cooler. You can disconnect the hoses on other end and blow through oil into a bucket and if it's a bad enough leak you can literally hold your thumb over one end and blow through the other for a quick check and or pressurize it and let sit for a few.

IMO the oil pressure will be higher than the water pressure at any given time. The water shouldn't leak into the oil, the oil will leak into the water. That is what happened to me 2 years ago. Oil residue on the transome. No water in the oil.

That is correct most of the time what I have seen and the boat owner most of the time would state - my oil level keeps going down thinking possible ring seal or other areas of oil consumption.

Easy to pressure test oil coolers.

Keep in mind ---- water in the oil overtime is not good for bearing life.

this happened to me a couple years back, in my case more oil going out than water coming in but did have both happening. exhaust was very oily and when I pulled the engine did have some water in the oil pan but not enough that it showed on the dipstick.
if the price is right and you are really interested in the boat then even if you have to pay for it id have the cooler pressure tested.

The biggest red flag I see is that the previous owner wasn’t willing to fix something so simple. I would guess that he maintained the rest of the boat the same way, and a model of that long ago would likely need a full restoration, and I believe those Formulas were susceptible to rot.

Call the mechanic. Id bet good $$$ he said it “could” be the oil cooler.

Yup, never believe what the seller's mechanic says, get your own independent opinion.

That would NOT be the case if it was a customer of mine selling his boat. I can promise you that 110 %.