I recently bought this boat a few weeks ago — it’s a Pantera 28 Factory 1, formerly known as the “TravelNow” Pantera.

It’s powered by a 509 cui big block with a BDS 8-71 supercharger, and according to the dyno sheet, it makes 853 hp at 6000 rpm with 8.6 psi of boost.

This is a new boat and engine for me, and I ran it for the first time this past weekend.

At the rear of the cylinder heads, facing the transom, there are two crankcase ventilation hoses—one on each side—running straight up with filters mounted near the scoop.

After running a powerboat event out at sea, we cruised at around 4500 rpm for an extended stretch with 2–3 offshore stops. It was fairly rough out there, and the boat often stayed stern-heavy while getting on plane, with some occasional jumping in the waves.

When we came to a stop, we noticed that the cap on the port-side crankcase breather filter had blown off, and there was quite a bit of oil mist throughout the engine bay.

After letting the engine sit for a while, the oil level checked out fine—no major loss. However, the same thing happened again on the way back.

According to the previous owner, this issue started after the engine was rebuilt. He told me that “they” blamed the supercharger, though it’s unclear exactly who that referred to.

So now I’m trying to understand—what could actually be causing this?

Is this a common issue on forced induction engines (supercharged or turbocharged), where boost pressure leaks past the piston rings and pressurizes the crankcase? Could it be due to worn or improperly sealed rings?

The engine seems to run fine otherwise, showing 60–80 psi of oil pressure while underway.

Or is this just a typical side effect of running a supercharged engine, and the real solution is to install a proper catch can or breather tank to collect the oil mist from the crankcase ventilation?

Could it also be related to the rough sea conditions—with several hard accelerations and bow-high running when getting on plane? I’m thinking oil may have been pushed toward the rear of the valve covers, where the breather filters are mounted, causing it to blow out?

Are the breathers just poorly positioned, and would relocating them toward the front of the valve covers help reduce the oil mist escaping?

Im gonna do both compression test and leak down test to see the results.

Any thoughts or experience with similar setups would be greatly appreciated!

Thanks!

Nice boat! I had an 871 blower on my previous boat and it would also mist oil through the breathers. It wasn't bad enough to influence oil levels or pressure but it sure did make a mess of things. I just ran the boat like that for five years and wiped down the motor a lot. The person who bought the boat from me immediately installed a catch can to solve the problem. I'm not an expert but I think you're on the right track with this thought: "Is this a common issue on forced induction engines (supercharged or turbocharged), where boost pressure leaks past the piston rings and pressurizes the crankcase?"

this is common. crank case pressure builds in bottom end, leaks past the ring pack, into the heads and out of the breathers. Motion raceworks sells a nice catch can/breather, along with many others.

we use them in situations where ethanol based fuels are used to catch the excessive amount of moisture

Thanks a lot, both of you — I feel a bit more at ease now. I was already thinking about installing a proper catch tank and running both breather lines into it, with a drain plug at the bottom and a filter or vent on top.Right now, it’s set up with two large silicone hoses running from the rear of the valve covers up to a pair of breather filters mounted near the scoop.

When I noticed the oil had blown out, the cap on the port-side breather was gone — so oil must’ve sprayed out all over the engine bay. Not exactly a fun cleanup…

My initial idea was to relocate the breather hoses to the front ports on the valve covers — where the oil fill caps are currently — and then move the oil fill to the rear ports instead. I’m thinking that when running in waves, with lots of bow-up motion during acceleration and stops, the oil might be sloshing toward the back of the engine and into the breather lines. Combine that with high crankcase pressure, and things can get messy fast.

So the current plan is to ditch the silicone hoses altogether and replace them with proper AN lines and fittings. I’d mount them to the front of the valve covers and route both lines back to a catch tank, as described — just to clean up the setup and avoid more oily surprises.

Let me know if that sounds like a solid approach or if there’s a better way to do it on a blown setup in a boat.

I would install a vacuum pump.

I had Stainless Marine add pan vacs to my tailpipes. Eliminated any residue from blowby.
468's made 595hp @ 6800

You need a catch can.

Do you want to show me what you mean and where you would install the vacuum pump?

Do you mean routing the ventilation down to the exhaust tips? If so, I have a friend who has that setup, but then I maybe don’t know how much oil it throws out.


I was considering the Moroso 85393, but I prefer the ones with a glass tube on the side so you can see the oil level.
Moroso 85393
Like this one with a glass tube I mean
Catch tank with glass tube

https://www.gzmotorsports.com/VP104-vacuum-pump.html

A fresh engine with properly seated rings should have MINIMAL blowby. But, YES, a supercharged motor will always have MORE blowby than a NA motor.
1) are your valve covers baffled ? Proper splash guards are helpful. If you have provisions for adding brass wool/mesh to the baffles, that's even better.
2) catch cans are a useful bandaid. Be sure to place it where it is easy to drain. Drain regularly/frequently so you can notice any "increase" in oil collection.
3) a leakdown test is ALWAYS good on a motor to establish a set of baseline values that you can compare later to know when things are deteriorating more quickly. You want to see cylinder to cylinder values less than 13% and variations of no more than 5% cylinder to cylinder.

Good luck