tccombs

engine considerations.

58 posts in this topic

I just posted part of this as  a response in another thread and thought maybe this should also be its own topic as well. 

I've been learning a lot about boat engines  that i never knew before and thought I might share some of what i have learned. 

 

Okay, Here is a Reality check to help you choose your engine...   You really need to think about what engine is appropriate for your boat. 

We All tend to always want more power..   More power must be better right?  ... But please consider that a bigger more powerful engine is not always the "best" idea for what you are using it for...    

My boat is an 2006  response LXI   I got the upgraded Hammerhead 383 engine.. this engine spits out 400 HP.  and a ton of torque.   And i take great care of it. 780 Hours  ( a stroker 383 engine means you have taken a 350 base engine and put new crankshaft and other parts in it  that result in higher displacement of 383. this essentially is pushing the engine HP and torque higher that it was originally designed for. )  but they can be bought from GM and Indmar and Mercruiser like this.   I didn't touch mine. 

 

On the plus side...  400HP is fun! 

1. It sure it is fun to out run  every other inboard waterski boat around me  when i have it flat out at 50MPH.  

2. And it sounds awesome! 

3 More power than i ever really needed. 

 

On the minus side. 

 

1  more power than i ever really needed

2  It sounds awesome( but also loud and hard to hear others) 

3  I don't really need to run at 50 MPH for any real reason not even bare footing 

4 It requires premium fuel 

5 it burns through the 42 gallon tank  in a day and a half of  normal activity.   AND At full throttle it will Drain the whole tank in an just two hours.     back when the price of premium was high  5.25 a gallon..  that works out to $200.00 in gas for the weekend  and that didn't even include the gas for my truck to tow it. 

 6 It is a stoker motor  so it burns a bit of oil..  1 qt every 20 hours   (this is normal) 

7 that motor was about a $4000 extra over the standard 

8  the standard motor will get you to 45 MPH.  this  one gets you to 50   (that is a lot of money needed to get 60 extra HP  only to get  a 5MPH difference  which also clues you in to just how much resistance that water is giving you at those speeds) 

9 the engine redline turns at a higher RPM 5200  so you have to put a higher pitch prop on the boat  13x13   vs  standard 13x12  to keep it from hitting red line

10 since it is proped higher it puts more  torque strain on the prop shaft.. my prop shaft broke the year before last.  

11 That puts additional strain throughout the transmission and  t engine crankshaft  as well as all the parts.

12 In a car you may have a 400HP engine but 99% of the time You are not using all the HP and torque and your RPMS are below 2000 RPMS. Only 1% of the time are you using the engine to its full capability. When you  compare that to a boat it is the opposite.   Your boat  is running at nearly  full power and full torque . which is above 3000 RPMS  combined with (tremendous drag from the water   which is why we dont need brakes )its entiire life.    This puts tremendous strain on the entire driveline.

13 some of those driveline parts may not  all be up for that kind of abuse that comes with that combination  of   High torque, High Horsepower, AT High RPMS  for long durations . Which is exactly how we use these boats most of the time. 

14  how do i  know all this? Well my Crankshaft just broke.  I have been talking to a lot of people lately and am learning quite a few things.      and now  i need a whole new engine..  it is clearly a manufacturing defect in the crank  as it happened  not inside the engine but rather where the harmonic balancer attaches.  ( this is very rare) 

15 Can it be fixed?  yes, but it is more cost effective to simply get a whole new long block engine with a warrantee

16 How much does a new Indmar 383 cost?    About $8000. 

17  some mechanics dont want to even  work on them because the specs are so finicky.. 

18.   We drivers all tend to push our boats to their limits.. sacking them out  with ballast, Wedges,  People and stuff,  not to mention the massive 100lb beer cooler for everyone. Then try to run our boats hard on them. 

Well that engine of mine is based on a Vortec 350  small block.. that originally was meant originally for cars and pickups and produced about 250Hp   well now we are pushing that same platform to over 400HP..  and using every bit of that power frequently.. so no wonder things start breaking..

 

I dont know about you...   But i am going to stay away from stroker motors in a boat..  instead if you need the HP move to a big block that will be better equipped to handle the stresses.. 

For me.. i think the best upgrade to my boat might just be a downgrade in the engine

I'm thinking  seriously about putting in a regular 350  because it will perform nearly as well  but without wanting to tear itself apart at just 780 hours..  

Edited by tccombs

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That is interesting to hear.  I am going on 2 years of a custom built 388 stroker, and have a different view point.  I'm not trying to create an argument, just offering a different opinion.  My engine was built not to any specs, but by a person on TMC that knows engines and boats, so his goal was to pair up that info into a good solution.

1. Mine dyno tested at 385hp running 89 octane gas, standard 10 degrees BTDC timing/34 full advance.  So it does not require expensive fuel

2. It has more power than I need, which means I rarely get on it WOT (ACME 425 13x13 prop 49mph GPS at 4,900rpm).  So the extra power has a great benefit of saved fuel and stress, because I simply don't need to push it hard to get what we need (footing, surfing, etc.).

3. I customized the exhaust, with ETX manifolds (I think you have those too), removed the guts out of a silent rider muffler and opened the rest back to 3.5" all the way to the STE's.  I think it is actually quieter than the stock 265hp engine was, and even one of my kids commented the same when we first got it going.  But I think it has more outside-of-the-cabin rumble.  To me it sounds fantastic, but quiet enough so my wife did not say anything about the noise level (and she's picky!).

4. The drive train for my Echelon was also used for the 454 option, same prop/shaft/strut/transmission.  So the stress would be the same as a big block.

5. I actually have 2 Echelons right now - an open bow with the 388 and a closed bow with the 454.  The 454 is much harder to work on.  I thought with it being a direct drive, that it wouldn't matter, but there is extra cooling for the fuel lines which basically wraps them around the engine, and getting to electrical connections and hoses is a PITA.  There is a lot jammed into that engine compartment - way more than with a SBC.

6. My initial thought when my original 265hp engine failed (due to impeller failure and overheat) was find a 454.  But none were available and a crew member on here offered to custom build an engine, so we went with that.  But I always wondered if I would have been better off finding a stock 454EFI instead.  Now that I have one, I am much, much happier with the SBC 388.

One more note - you are comparing horsepower, but not torque.  So going from 340hp to 400hp is about an 18% increase, but I'd be curious to see what your torque gains are, and those are typically reflected on the lower end of the RPM's where you really need it most.  I'm guessing with the longer stroke and different cam more like 30% increase.

So there ya go!  Just some other things to consider.

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I know torque is also considerably higher than a 350...    however I have never been able to locate the exact number from Indmar.   let me know if you find it. 

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The only time the driveline sees no more stress from a more powerful engine than a less powerful one except under acceleration.  When maintaining speed, the resistance force is the exact same no matter if a four cylinder or LSA is in the boat.  

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Just to reply to your downsides:

1.  So what.  Doesn't hurt to have it.  How is this a downside?
2.  I'm sure a 350 would be about as loud in your boat.  Get some STE's (I happen to have a pair for sale).  That will cut the sound down a lot. 
3.  Again, not really a downside
4.  That can be a downside, but premium is only $0.20 - 0.40/gallon more, so the cost isn't that significant
5.  The question is would a standard 350 burn the same?  I think it would, especially if both were propped for similar performance
6.  That's because of the design of these motors, not because it is a stroker.  Other engine upgrades don't have this issue - this is a complaint about your engine model and shouldn't be part of the list of downsides to a motor upgrade
7.  That's is a real downside.  Should also be considered that if buying used, depending on the boat, this price difference may either be totally or mostly lost in resale (so non-factor for used buyers) or nearly 100% made up in resale (bad for used buyers, perfect sense to upgrade for new buyers).  Bit of a case-by-case basis here.  So this may/may not be a downside.
8.  Not sure how this is an up or downside
9.  This is an upside, not a downside.  You have more RPM to play with.  You can go with a less aggressive prop if you want to keep RPM's down even further
10.  Your prop shaft failing has NOTHING to do with your motor making more power.  There are guys running much higher HP motors than you with the same propshafts without issue.  Most likely either something damaged the propshaft or a defect in it
11.  Additional strain yes...strain it is designed for.  Even a budget 350 crank can take more HP than your motor makes with ease.  Transmissions in these things (and V-drives for those of us that have those) can easily handle the power and more.  Non-factor IMO
12.  Though I disagree with your percentages, the bottom line is this factor has nothing to do with a pro/con of having an upgraded motor
13.  Disagree.  The LS3 guys have been abusing these with tons of weight, high speed runs, etc. for years.  Same parts, more power, heavier boats than yours.  
14.  Again, nothing to do with a motor upgrade but rather the motor upgrade you have.  It is know as one of the least reliable of the Malibu motor options
15 / 16.  Not sure how $8000 is cheaper than a simple rebuild, unless you trashed the block & heads.  The GEN-I SBC is one of the most commonly rebuilt engines in the world and has the largest aftermarket part selection of any motor...simply put, if you are going to rebuild a motor, that is the one to rebuild.  Warranty is a different discussion of course and really depends on who is doing the work and what warranty they provide.  
17.  What engine tech doesn't want to work on a common GEN-I SBC?
18.  Again, not sure where this is a downside of a motor upgrade

The issues you are having, very simply, are from bad luck on one of the least reliable motors Malibu has used in the past couple of decades (and it really isn't all that unreliable).  I think you may have a jaded viewpoint because your motor has had issues but I 100% disagree that people should avoid motor upgrades based on your experience.  I am VERY glad I have the upgraded motor in mine.  

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@tccombs in my 2014 24MXZ i ordered the LS3, it worked fairly well, but i had to push it so hard to push the weight.  I propped down to a 15x12 (2419) and fully weighted she would only hit 43-4400 RPM at WOT.  It would run there at 11.4, depending on crew i would have to drain water to get to 11.4.

So my 2015 I ordered the LSA, I was able to prop up to 15x15.5, and still hit rev limiter, fully loaded.  Even running more weight than the 2014.    However i saw an increase in fuel efficiency, due to running ~3500RPM vs. WOT on LS3.    

So there are some benefits to bigger engine.

I do absolutely agree that as surfing becomes more and more popular and folks are adding more and more weight.  The drive train takes a BEATING!   I too experienced a few drive train issues, likely due to the workload of heavy surfing.  However the solution is not a smaller engine, its beefier driveline, tranny, etc.  Most newer big boats are using 1 1/4 driveshafts now, PCM is claiming tbey reinforced tranny to account for greater torque, and 16-17" props are becoming the norm.

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@tccombs:  You will find the hp and torque specs for that engine on the GM Powertrain website:  http://www.gmpowertrain.com/MarineEnginesControllers/Introduction.aspx

The data will be very close to the output from the marinizer, they will differ a bit due to some specific calibration differences.

As for the concerns / comments noted above I will add some random notes:

  1. we all like extra power, sometimes at least until we have it.  For barefooting it is mostly beneficial other than a less than delicate driver on acceleration.  For slalom and specifically the course the additional power can be a significant detriment to achieving best scores if the boat simply overpowers the skier.  ZO speed control and some experiments underway now are clearly highlighting that.
  2. Stress on the drivetrain are not necessarily be engine speed related, it will be more a function of where in the torque curve one is operating and probably more importantly how well the drive train is aligned.  Resistance due to boat loading will also have a significant impact.  One hears very few incidents from the barefoot crowd and they (we) spin the drivetrain faster than other uses so engine speed is not necessarily the major culprit.
  3. Just for some humor, 85 barefoot comments relative to the power source v stress, correct as for the resistive force is the key and the new CNC high grip props actually increase stress compared to older versions, but my comment would be that a 4 cylinder engine would actually create more stress on drivetrain due to fewer, thus less smooth input firing loads compared to an 8 cylinder.
  4. the stroker engine oil consumption should only be slightly higher than a non stroker due to piston speeds, the choice or ring package and bore finish are more of an issue than piston stroke if oil consumption is drastically different.  As for fuel consumption, with a longer stroke the power curve should allow the boat to be propped taller thus reducing engine speed at a given boat speed to reduce fuel consumption.  Hull resistance should be the major driver on fuel economy.

@tccombs:  If my boat, I would look at drivetrain alignment both static and perhaps in your typical or highly loaded condition.  Good luck sorting out the component issues.

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nitrous...

I agree with some of what you are saying...    I agree the hammerhead is not the best example..       But i think you may have mis-interpreted my point.      

 I am not trying to discourage people from upgrading engines across the board.  That is not the message i am trying to send. 

I am trying to explain some of the factors that they should be considering when deciding what engine to use.  Many people simply think  more horsepower MUST be better in just about every way.  nd think no further than that  they stop there.  But dont consider some of the other factors  that can show up years later

At the time I bought my boat I had not considered many of those factors..   Years later  this is what happened.    

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39 minutes ago, Woodski said:

@tccombs:  You will find the hp and torque specs for that engine on the GM Powertrain website:  http://www.gmpowertrain.com/MarineEnginesControllers/Introduction.aspx

The data will be very close to the output from the marinizer, they will differ a bit due to some specific calibration differences.

Very interesting.  I had heard that the torque was not so different but had no idea how close they were (excepting the super charges LSA):

L83 5.3L - [email protected]100

5.7L Vortec - [email protected]

6.0L Vortec [email protected]

LS3 6.2L [email protected]

LSA 6.2L [email protected]

L86 6.2L [email protected]

What this tells me is that for surfing in the 3000 to 4000 rpm area there is really not a big difference in the engines (excepting LSA), especially at the lower end (e.g. 3300 rpm).

What would also be interesting would be fuel consumption comparison at a given power output.  The engines would have different throttle settings of course.

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What is interesting to me is that the 5.7L makes its best torque in a usable RPM range, where the other engines are really having to scream to get into their max torque

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16 hours ago, oldjeep said:

What is interesting to me is that the 5.7L makes its best torque in a usable RPM range, where the other engines are really having to scream to get into their max torque

If you believe those numbers...

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I like when the engine loafs along at 36 MPH instead of screams at you when pulling good slalom skiers.  I also like having a 50 MPH boat just because.   

Edited by jjackkrash
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On ‎12‎/‎14‎/‎2016 at 1:57 PM, tccombs said:

14  how do i  know all this? Well my Crankshaft just broke.  I have been talking to a lot of people lately and am learning quite a few things.      and now  i need a whole new engine..  it is clearly a manufacturing defect in the crank  as it happened  not inside the engine but rather where the harmonic balancer attaches.  ( this is very rare) 

Couple of thoughts:

A 383 stroker can built either internally or externally balanced, or a combination (front external, rear internal).  With an externally balanced engine, an unbalanced flywheel and/or harmonic damper is used to balance the unbalanced engine.  The unbalanced damper will put extra stress on the crank snout as it spins.  GM/Indmar 383's are externally balanced. 

Another thing that can cause extra stress on the front of the crank is the way Indmar started mount the raw water pump, cantilevered off the front.  With that thing sticking out there, any out of balanced is sent straight back the front of the crankshaft.

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yep  that is all correct Madman..  

 

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On 12/14/2016 at 2:57 PM, tccombs said:

For me.. i think the best upgrade to my boat might just be a downgrade in the engine

I'm thinking  seriously about putting in a regular 350  because it will perform nearly as well  but without wanting to tear itself apart at just 780 hours..  

So are you still thinking of doing the straight 350?  Will your intake and ECM work with it or will you have to change that stuff too?

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If I go that route.. I  believe the Intake will still work.. but I know I will need to replace the ECM

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15 hours ago, tccombs said:

If I go that route.. I  believe the Intake will still work.. but I know I will need to replace the ECM

Did the crank failure ruin the block?  Can you just replace the crank?

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A few thoughts.  First, it is my opinion that the reported engines in marine use bear little to no similarity to the ones in automotive (and I like to think my opinion is educated since I used to do engine development for a living).  For example, the 350 iron block, iron head engine in my boat makes "350 horsepower" yet only made about 225 horsepower in its highest output application in the auto world.  It may be a gross/net thing, noting that the way the auto world rated cars prior to the early 70's was drastically different (and it was tightened up again in 2006).  So, don't compare the two, they are not the same.  It can be difficult comparing even auto to auto, as different vehicles have different requirements for NVH, and the weights/loads will affect how aggressively they can be tuned (e.g. a Mustang with a 5.0L can be tuned much more aggressively than an F-150 since it won't spend prolonged periods of time (several seconds to much more) under heavy load which lets things heat up.

Second, the stroke increase is not out of nowhere, nor is it exclusively aftermarket.  Chevy made a small block 400 based on the same architecture.  It has a 3.75" stroke (which I believe is what the 383 uses), but with more bore.  I think that MadMan pretty much nailed all of it above, so I can't add much.  But just wanted to give you a little more background given the comparison to the auto world.

Also for those commenting on torque, where it is, etc.  The single largest factor in the value of that number is the displacement.  A 383 will produce roughly 10% more torque then a 350.  Where it makes it will tweak it a little, but the value of it should fall roughly in that realm.  That's within an architecture, as stuff like OHC or DI will improve torque across the board.  As for where in the RPM range that falls, that will be tuning of the airflow controlling components of teh engine (NOT "tuning" as in PCM calibration).  Intake runner length is the primary contributor there, but cam profiles and exhaust runners can tweak it a little.

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On 12/15/2016 at 1:02 PM, oldjeep said:

What is interesting to me is that the 5.7L makes its best torque in a usable RPM range, where the other engines are really having to scream to get into their max torque

You need to see the entire torque curve to make a judgement on that. The RPM where the peak occurs is useless. A engine that peaks at 440 ft lbs at 4600 rpm but still makes 400 ftlbs at 2200 RPM is far better then a engine that makes 440 ft lbs at 3600 but only 300 at 2200. A flat torque curve with a large RPM range generating good torque is what you want.

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Status update.. 

 

JT  at Indmar was great!   Despite this engine being 10 years old and well out of warantee,   They realized  the break in this crankshaft   should never have happened.    So He went to bat for me..  and got approval to offer my mechanic a  special deal on a new engine at 15% off.  which  hopefully would be passed along to me.  since they cannot sell dircect.     But since indmar no longer makes this engine  it would be  a 350  and not the 383 stroker motor..   this would mean that we would also have to get a new ECU..which would add an additional 1000..  

 

as a result it would still be more than just rebuilding my  383 

 

So i made the decision  not to get the new motor and instead do a full rebuild. 

 

I removed the engine.   

My mechnic  knew about  a common g problem  with the aluminum ETX  cat exhaust manifolds..  and caught a problem the second he saw it...   apparently  these are prone to corrosion at some of the  weld points  that can result in  water leakage.    My exhaust was no exception..  so they rewelded those points on the exhaust..

after the engine was pulled and sent to the machine shot...  

The good news was there does not seem to be any internal damage from the crank..

But the bad news was that  they found that some water got into two of the cylendars. from the exhaust   So they had to bore it out .20 over to clean up the block.    

The crank  is very rare and turned out to be a special order from SCAT.   $700  it was supposed to be a 3 week wait.. but we got it in 1 week...  Nice job  SCAT! 

So we are now trying to replace the pistons.   Now it turns out those seem to be hard to find too.. we may have to special order those as well.        

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On 12/14/2016 at 1:24 PM, tccombs said:

I know torque is also considerably higher than a 350...    however I have never been able to locate the exact number from Indmar.   let me know if you find it. 

i have the HP/TQ curves for the HH.  Let me see if I can find it.

Lots of HH's had problems.  from the infamous dip stick to  other problems.  the engine was not balanced well and vibrated a lot.  and was not the best engine for marine use, as it got it TQ at a higher rpm than the 350.

And the LSA will deliver more TQ to the drivetrain than the 4 cyl.  When you accelerate,  the LSA will get you to say 40 mph faster that the 4cyl.. So the LSA creates/generates more TQ in a shorter time frame that your 4cyl.  Which put more stress on the drivetrain.

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So I don't think the stroked engine is the issue. Can you get a picture of the crank end at the brake? Close up but clear. I am willing to guess its going to tell a story. The crank is not modified  at the harmonic balance  end for stroking. It will be easy to tell how long this has been coming apart.  Tell us more about your drive line breakage.  It could be related.  I have run stroker engines for many years at 8,500 / 9,200 rpm for years We also ran many desroked engines. As said stroking in itself will not increase oil consumption  but depending on the build you could see more oil consumption. Just so much more then you are thinking.  Oh I have the 07 R lxi with LCR ( standard engine ) it tops out with just me in it at 49 MPH  stock prop. Give or take one MPH on water and wind conditions not extreme.  The more HP is more often for getting the skier out of the water and up to speed in A shorter time and distance.  Course skiing its a big benefit.  

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Posted (edited)

On 12/15/2016 at 7:02 PM, oldjeep said:

What is interesting to me is that the 5.7L makes its best torque in a usable RPM range, where the other engines are really having to scream to get into their max torque

It doe not exactly work that way. Torque is what accelerates the boat. HP keeps it there at speed. Most newer BU's when accelerating are over 4000 RPM. That is where you want your peak torque. As I posted before you also want a broad flat torque curve. A engine making 85% of peak torque from 2000 RPM up to the peak at 4400 rpm is more useful then a engine making peak torque at 3500 but not seeing 85% until 3000. The new Fords don't look that impressive on pure numbers but have shown in actual use they can swing a lot more prop then a 5.7 Chevy. 

On the earlier post about the prop shaft breaking I think how much weight you run in the boat is more critical to the shaft then the engine HP. When the G23 first came out in 2013 they broke a lot of shafts. I don't think it mattered which engine was in the boat.  They went to a 1 ¼" shaft which seems to have solved the problem until this year. There are some broken shafts showing up again. It may be that when pushing 10,000 plus lbs of boat and water a 1 ⅜, or even a 1 ½  really is needed. 

Edited by Sailvi767

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24 minutes ago, Sailvi767 said:

It doe not exactly work that way. Torque is what accelerates the boat. HP keeps it there at speed. Most newer BU's when accelerating are over 4000 RPM. That is where you want your peak torque. As I posted before you also want a broad flat torque curve. A engine making 85% of peak torque from 2000 RPM up to the peak at 4400 rpm is more useful then a engine making peak torque at 3500 but not seeing 85% until 3000. The new Fords don't look that impressive on pure numbers but have shown in actual use they can swing a lot more prop then a 5.7 Chevy. 

On the earlier post about the prop shaft breaking I think how much weight you run in the boat is more critical to the shaft then the engine HP. When the G23 first came out in 2013 they broke a lot of shafts. I don't think it mattered which engine was in the boat.  They went to a 1 ¼" shaft which seems to have solved the problem until this year. There are some broken shafts showing up again. It may be that when pushing 10,000 plus lbs of boat and water a 1 ⅜, or even a 1 ½  really is needed. 

Malibu and to a degree Indmar should be installing truck engines in these boats, rather than a a corvette engine or cadallic engine.  Many have talked about these boat being tractors or tug boats.  SO these boats need a truck engine.  Generating more low end torque.

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Posted (edited)

23 minutes ago, WAwinegrapes said:

Malibu and to a degree Indmar should be installing truck engines in these boats, rather than a a corvette engine or cadallic engine.  Many have talked about these boat being tractors or tug boats.  SO these boats need a truck engine.  Generating more low end torque.

67 (being an engine designer/development) should be able to better  explain the difference between a LS3 corvette engine in Malibu boat and a truck engine.  both the heat generated and dissipated and other low end TQ requirements/needs.

 

http://gmmarinepower.com/products.html

 

https://www.corvetteforum.com/forums/c6-corvette-zr1/2721776-ls9-vs-ls7-vs-ls3-power-and-torque-curves.html

Edited by WAwinegrapes

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