How does Nautique do it?

[jhughes]

This is not a slam on any other manufacturers, there are things I love about all of the big 3 ski boats out there. This is purely, purely out of engineering curiosity and nothing else. Not hinting that any design is better or worse in this sense. What is Nautique doing differently in their engine clamshell or venting design that allows them to not have any vents or fans or anything and the engine continues to function just fine? And I'm not just talking about current boats, I mean for years and years. Malibu has had a rear vent for a while and MC had a fan and now a really clever vent on the 21. My 16 SN has a current engine (5.3DI) and no venting on the engine box whatsoever, I haven't taken a close look at the Polygon Nautique yet but I'm assuming no vents on that either. Anybody know?

[Horton]

@jhughes How do you know that the heat (lack of venting ) in that engine box is not negatively impacting performance?

[skimtb]

Polygon nautique. That’s funny.

[acmx]

Engine box on CC200 is vented to gunwales/ saddle bags. Kind of odd config but works great.

[BraceMaker]

Suppose if you own the engine mfg you can have it not power derate for the engine vent temps too ;)

 

All these boats have some form of way for air to come into the engine - a V8 pulls hundreds of cubic feet of air a minute depending on several factors but the point being so long as there is a pathway there will be airflow. The 200 closed bow has a vent under the window so I'd assume there are atleast a few air inlets in a similar location on the OB version - maybe just inside the window or in the walkway with a louver.

[DavidN]

I am always wondering the same.

Where does that big V8 gets all the air to breathe?

 

Interestingly the “vent” under the window of the 200 CB is just cosmetic and not functional. It’s basically a vent cover screwed on top of the gelcoat. No opening behind it!

 

 

[jhughes]

There are no vents on the front of the OB 200, decorative or functional. The saddle bag vents seem to vent the saddle bags (only) clearly and the saddle bags could in theory be filled with stuff so I don't see those being some big ventilation chamber or flow path. There are two rear facing transom vents that I suppose could feed down to the bilge.

[skimtb]

Bigger Flux capacitor?

[UWSkier]

Sounds like it'd be a good submarine.

[DW]

For reference, WOT air consumption is in the range of 600 cfm.

[BraceMaker]

@DW can reference carbs too where a 700 cam Holley is huge airflow.

 

It’s physics the engine is breathing something or else it’s Going to be manifold vacuum.

[WoodySkier]

There is a small chrome fitting on the drivers side up by the bow which I believe is air intake

[DavidN]

@WoodySkier

That would be the horn. ;)

[The_MS]

For 110k on a new CC they better do it right.

Even for 50k they better do it right.

 

[DW]

Its a 15 second math problem.

[skierjp]

Too my knowledge and experience Nautique has never had a air issue. You do see other brands with the motor box open and or cup holders missing. You can't go wrong with PCM.

[Jody_Seal]

Devine intervention!

[MISkier]

I heard they cool the air by lining the inside of the intake with a special coating made from the pulverized dreams of now defunct boat makers without the cozy relationship to the sport.

[Mancy]

If you spend that much money for a boat you just don't let anybody know if it overheats or has other mechanical issues. Has anybody ever heard of any issues with micro tuners or the hydro-gate on the new boat? Funny how nobody talks about it. Who knows maybe they do overheat.

[KRoundy]

My 200 OB runs cool and has plenty of oomph. Wherever the air comes from it is enough and I love how quiet my boat is too. I have yet to have any problems with my Nautique. Great boats designed by great engineers and skiers, built with great craftsmanship and innovation.

 

I personally think that this is an awesome time to be a slalom skier. So many options - 3 great new machines by the big three. If you don’t have or don’t want to spend that much, there are some GREAT used options available. I enjoy skiing behind my 200 OB and then the next day will enjoy skiing behind my friends 2003 Nautique just as much! Then the next day we will take some turns behind another friends MasterCraft. They all have their quirks or differences, but all are a blast to ski behind!

[Fast351]

If you look at the amount of air that flows through a Holley carbureter through basically 4 golfball sized holes you can imagine it doesn't take a big tunnel to flow enough air for intake. A 4" dryer duct somewhere would do it.

 

Engine cooling is a far more interesting issue, although with raw water cooling I can't imagine that the engine generates much external heat that would create problems.

 

 

[JuanJ]

Our 200 OB Nautique works better with the blower on at altitude. (7000 feet above sea level).

 

[lakeaustinskier]

As far as heat - does anyone prop open their engine cover after they run the engine to vent the heat and moisture? I'm just talking about using a small piece of wood to slightly crack the cover open. A boat mechanic told me one time to do this since it helps extend the longevity of the rubber and keep moisture out of electrical parts......my ski partner thinks I'm nuts. Opinion?

[DavidN]

@lakeaustinskier

In fact I do. A 5 Inch long piece of 3/4” PVC pipe fits perfectly over the locking pin of the Nautique box, sits pretty secure in the lock and keeps the engine box cracked enough so the heat can dissipate.

[BraceMaker]

@Fast351 people get suckered into the whole open water cooling being efficient. There is a huge problem with open circulated cooling and that is the amount of energy water can store at atmospheric pressure in order to remove it from the head/block with out boiling. Fun physics exists.

[Fast351]

@BraceMaker hadn't even thought about that. No pressure, not nearly the thermal transfer. Of course there is nearly an infinite supply of it :smile:

[BraceMaker]

Ya supply could be upped - there is a practical limit due to the coolant passages on engines which were ultimately designed to be pressurized in cars, and contamination due to sediment and minerals in lake water that cause deposits that create point boiling.

 

People see 160/70/80 on the gauge and think the engine is running cooler than their truck at 210+ degrees and think the engine is doing great, but that's water temp in the thermostat housing with a mixture of incoming raw water and outgoing water from the block - it can be much hotter in the heads. LT-1 Mastercraft were famous for boiling off water in their reverse coolant heads - once it started boiling the pressure the water gave off with boiling would blow the coolant out of the heads and no matter how cold the incoming raw water was.

 

With a pressurized cooling system and ph/mineral balanced coolant with no deposits you can ramp up the temps - get a more efficient engine and have fewer hot spots.

 

This is some of the issue with boats - you can actually have localized heat issues that won't show up on gauges or sensors but will create things like vapor lock or heat related power reduction.

 

 

[UWSkier]

It'd be interesting to compare the IAT sensor readings on a 200 with the IAT sensor readings on a 2017-2019 Malibu TXi on the same day if they both have the 6.0L. I can't imagine the SN motor box without any venting retains less heat than the Malibu design with obvious ingress and egress points.

 

IAT sensor reading is visible on the diagnostics menu on the TXi. Does the SN have a similar screen capability?

[DW]

Block and cylinder head pressure will be 'controlled' (ie: loosely) based on raw water output v volume of water passing through the t-stat (-the bypass circuit effect). I have not seen or heard any test data numbers on what that ends up being. Can't be much, and as pointed out, pressurized systems increase boiling point (high pressure systems can run very high temps w/o boiling).

[Fast351]

@BraceMaker Sounds like the closed loop cooling systems are superior for more than just keeping minerals and sediment out of the engine.

 

Am I right in assuming that closed loop systems are pressurized like cars? (I've never owned one)...

 

[Jody_Seal]

Our ski partner has a 17, 200 CB 6.2 that keeps putting up IAT codes. But only on 95 plus temp days... once we start a multi skier cycle the error goes away.

[UWSkier]

@Jody_Seal that sounds like the Malibu reports too. If it's pumping enough air, IAT warnings go away. If it's idling at course end for a while on a hot day, IAT warning comes back as the hot air settles up by the intake.

[BraceMaker]

@Fast351 exactly - and that pressure keeps the coolant in a liquid stage to a much higher temperature than an open atmospheric system. But its not without issues, you add complexity by having the heat exchanger and extra plumbing for the closed loop - plus you still have lake water going through the heat exchanger and then into your exhaust manifolds. But then again you can get the engine block to real "warmed up" temps which could make the IAT higher.