Oil for Extreme Marine Endurance Application?

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We race Marathon Whitewater Jet boats, 366 ci SBC with larger than normal main and journal clearances (.029-.030 in.) because of the extreme and numerous shock loading the engines endure. We race for long periods of time at a steady WOT and the motor may see over 400-500 incidences of shock loading as the boat leaves and returns to the water per weekend. It is not unusual for guys to turn bearings or break the balancers of the front of their cranks if their not careful. We've been using Joe Gibbs XP3 (10w30) race oil and have noticed some unusual bearing wear as this oil is designed for clearances in around .027 or less, so we're thinking about changing to a heavier grade. We've also noticed much more corrosion in the engine at the end of the year than we would like to see as Joe Gibbs has no corrosion inhibitors in their Race oils. So, we're looking for a heavier Extreme duty oil and are considering Mobil 1 HP 15W50, Amsoil RD50 Race oil 15W50 or Joe Gibbs XP6 15W50 (and learn to live with the corrosion issues). We're hesitant to use Mobil 1 15W50 high performance as it seems like a generic high performance oil not a purpose designed Race oil and we have no first hand information on Amsoil at all. Our engines cost about $40,000 each so we like to get as much verifiable and objective information on what we need and use the best products we can.......within reason. I would like to hear your comments and recommendations. If you do recommend to use or not use a specific oil, please provide details to support your opinion. Thanks in advance.
 
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First person I'd talk to is my engine builder. What do they suggest and why? What is your competition running and why do they run it?
 
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Straight 40 or 50 wt with those clearances Depending on the oil temps and the pressure. What is the hot oil pressure? You also have to change the oil often!!! [.0029 to .003 clearances?] .030 bearing clearance needs to run straight STP.
 

Riverracer

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Competition is running all different types from Mobil 1 to Joe Gibbs XP6. Even though we do preheat the oil We need to run a multigrade to give us lubrication on cold start up as we coll with raw cold river water. A straight 50 wt would be like molasses and would not be suitable for our climate.
 

Riverracer

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 Originally Posted By: bretfraz
First person I'd talk to is my engine builder. What do they suggest and why? What is your competition running and why do they run it?
I don't have any faith in either of my (ex)engine builders. We've had far fewer problems when we do the work ourselves.........and these are the best engine builders in a 1000 mile radius.
 

PT1

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I would check the Brad Penn line of high performance oils. They will have a suitable weight for your application. Also, take a look at Redline 20w60 Vtwin Motorcycle oil. Amazon.com had it on sale $95/case of 12 qts.
 
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I'd reach out to some of the specialty blenders like Royal Purple, Brad Penn, Redline, maybe Amalie, NEO Synthetics and talk to some of their engineers who work with various race teams. I'm sure they would have some insight as to what has been successful for their clients. Note: I found this on Redline's website describing their 15W-50: 15W50 The ultimate high-temperature protection in Red Line engine oils recommended for street use. Good for engines that regularly run very high oil temperatures. Best for engines that run large clearances such as air-cooled engines or large-displacement, all-out racing engines that see occasional street use. Provides 25% more viscosity in bearings than petroleum 20W-50s. Not recommended for use in cold climates where temperatures are at or below 10°F or -12°C. Not recommended for street use in production engines that see sustained oil temperatures below 225°F (those engines should use Red Line 10W-30 or 10W-40)
 

Riverracer

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 Originally Posted By: tom slick
Are you really running .029-.030 clearance? that's huge! or did you mean .0029-.003?
Your right - .0029-.0030. I have contacted all of the top performance oil suppliers and of course they all say they have the best oil for my application.
 
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 Originally Posted By: tom slick
Are you really running .029-.030 clearance? that's huge! or did you mean .0029-.003?
I'm curious too!
 
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I'd like to know which main bearings are getting pounded. Just the center mains? just the PTO end? ...or all of them?
 
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if I remember right it's any of them. These guys hook a huge pump directly to the engine and then the pump is pulled out of the water during racing. The clearances are needed due to the shock loads. I would definitely try that Amsoil 15w-50 racing oil. That's the real deal.
 
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With no other info, I think this "shock loading" is causing an abnormally large amount of crank flex. V8 cranks are, after all, very flexible; it's just that, in normal racing situations, they usually get to flex and 'ring' at the frequency they desire (or rather, the frequency that we design them to). This sudden load/unload situation is, without doubt, twisting the crank, and no oil of any attainable viscosity/pressure is going to be able to keep that level of torture in-check. . The crank/bearing wear pattern (front-to-rear) would give more indication of what's really going on, but then there's the problem that HE has the crank, and WE are all HERE. This is about the best we can do long distance. Without being your engine builder, I have to wonder if, failing all else, thicker oil, along with even greater M/B clearances (and the accompanying greater rod bearing clearance) would be sufficient to allow the crank to bend WITHIN the (now broader) hydrodynamic wedge area, therefore minimizing these metal-to-metal incursions. If so (and I think, depending on degree of flex, it would work), it would be down to weighing HP lost to the thicker oil/higher pressure Vs. the lower-wear benefit gain. In fact, since no catastrophic failure is being seen (so far?), greater bearing clearances alone may "fix" your problem. Your call, but my vote's in.
 
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Riverracer

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As mentioned in my origional post, we are aware that our cranks do flex and some guys do occasionally break their balancers right off. We're confident that because we haven't seen any catastrophic failures and only bearing wear, that our clearances are just fine and just a little heavier oil will clear up the bearing wear issue. Should I be looking for high shear abilities or what qualities should an oil have that would help protect the main bearings? So, this brings me back to my origional question, which synthetic oil would best suit our needs?
 
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One of the things with shock loading is the behaviour of the "squeeze film" that occurs as the parts come together. When you increase clearances, all else being equal, the velocities that can be achieved, one part relative to another will be higher, and the two surfaces become less "parallel". You need something that will resist being pushed out of the clearances, under a suddenly applied heavy load. Look for something that is relatively thick has no Viscosity Index Improvers, and for your cold water application good low temp pumping/pour points etc.. Maybe M1 V-Twin, or Delvac 1 would be a good base. Try the Delvac first, as 20W-50 might be too thick for a super cooled engine. Given that you have low engine operating temps, maybe molakule or Bruce can give some advice on additives that work well at lower engine temps.
 

Riverracer

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 Originally Posted By: Shannow
One of the things with shock loading is the behaviour of the "squeeze film" that occurs as the parts come together. When you increase clearances, all else being equal, the velocities that can be achieved, one part relative to another will be higher, and the two surfaces become less "parallel". You need something that will resist being pushed out of the clearances, under a suddenly applied heavy load. Look for something that is relatively thick has no Viscosity Index Improvers, and for your cold water application good low temp pumping/pour points etc.. Maybe M1 V-Twin, or Delvac 1 would be a good base. Try the Delvac first, as 20W-50 might be too thick for a super cooled engine. Given that you have low engine operating temps, maybe molakule or Bruce can give some advice on additives that work well at lower engine temps.
I completely agree, however as I understand any oil that is reccommended for motorcycles have no friction modifiers because of their wet clutches and therefore they would produce less hp?
 

salesrep

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[quote=RiverracerI completely agree, however as I understand any oil that is reccommended for motorcycles have no friction modifiers because of their wet clutches and therefore they would produce less hp?[/quote] Some oils with friction modifiers will work and work well in motorcycles with wet clutches.
 
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