Engine size debate again.

[Toaks]

Hello. I’ve found this topic all over the form but I wanted it to be specific to my situation. I live in Utah and will be boating at Willard Bay (elev. 4,220 ft) 85% of the time and at Pineview reservoir (elev. 5,000 ft) 15% of the time. I am looking at two almost identical 2019 Malibu LSV 25s. One has the M6i engine and the other has the 550 supercharged engine. I prefer the one with the M6i because of the deal I was able to work for it. About a 23k difference. I will be surfing and having at least 8-10 adults and 5-6 small kids in the boat usually. Is the M6i enough for this? Both have high altitude props. I don’t care about going fast just surfing and tubing. Will gas mileage be better with one over the other? Thanks for any input. 

[justgary]

A normally aspirated engine will lose about 15% of its power at 5,000 feet elevation.  For surfing, that should mean more throttle to get the job done.

A supercharged engine will not lose power at elevation.

[dizzygti]

I would want the SCed engine, but $23K is a song.  One thing is certain: you won't regret it if you can swing it.  I love my M6 but a crew that large at elevation is going to make it work.  

[Livinlogs]

1 hour ago, Toaks said:

Hello. I’ve found this topic all over the form but I wanted it to be specific to my situation. I live in Utah and will be boating at Willard Bay (elev. 4,220 ft) 85% of the time and at Pineview reservoir (elev. 5,000 ft) 15% of the time. I am looking at two almost identical 2019 Malibu LSV 25s. One has the M6i engine and the other has the 550 supercharged engine. I prefer the one with the M6i because of the deal I was able to work for it. About a 23k difference. I will be surfing and having at least 8-10 adults and 5-6 small kids in the boat usually. Is the M6i enough for this? Both have high altitude props. I don’t care about going fast just surfing and tubing. Will gas mileage be better with one over the other? Thanks for any input. 

I have the lt4 now and had the m6 before . I’m up in PC . The m6 just will require high rpm’s , you will be around 4000 regular side full weighted with people etc surfing. I love my lt4 but 23k it too much for the same boat . Buying new they are about 12k I believe over the m6 . What you might be seeing is resale values because 90% of what they order locally have the lt4 now in the 25 . Awesome boat no matter what . Play with props on the m6 . I never did . 

[dshack]

A buddy here in Utah had a 2021 25 LSV with the M6 and didn't complain, I think it's certainly doable with the right prop and wedge/RPM expectations. But, he went with the LT4 in his new 25 LSV due to the weight gain in the new hull.

For a $23k delta and not caring about top end I'd personally go M6. As mentioned above, the actual M6 -> LT4 upgrade cost for a new boat is about $16k MSRP (so maybe 12k with avg discounts). You'll probably have similar gas burn when you account for RPM differences.

Edited February 29 by dshack
Typo

[RyanB]

$23k is a ton of money.  But there isn’t much worse than spending 25 LSV money and feeling like it is under powered.  I know in Colorado pretty much every boat bigger than the 23LSV gets the LT4.

How long will it be before you could do a lake test?  It looks like our lakes will be opening in about two weeks.  For that kind of $, I’d want to try it on the water before settling.  Is there much risk in waiting?  Are boats in that price range actively selling right now?

[BlindSquirrel]

Has anyone ever supercharged the m6? If you find it underpowered, surely for less than $23k you could find someone that can?

[dizzygti]

37 minutes ago, BlindSquirrel said:

Has anyone ever supercharged the m6?

Does anyone tune these engines period?   

[Cole2001]

I would definitely proceed with caution. Marine engines run under load for much longer and more prone to overheats which can lead to cat failures. Not sure if they’re still around but there were a few companies making tunes for pcm but they had no real proof or reliability behind them. If something more reliable was out there it might be worth while. I’m 90% sure the difference between the 400 and 450 raptors is just a tune. 

[COOP]

2 hours ago, dizzygti said:

Does anyone tune these engines period?   

Not if they want any warranty.

[dizzygti]

44 minutes ago, COOP said:

Not if they want any warranty.

I'll be out of engine warranty after 2 years.   Care to explain in any more details?    I'm a powertrain engineer so understand elevated load and EGT's being affected by cam and ignition phasing, and that boats don't have multiple gear transmissions or grade/incline benefits here....but there is obviously power to be had on the table with adjustments.  Why is this so uncommon in the boating world?   

Edited February 29 by dizzygti

[DRB10SEVEN]

It would depend on how much power is actually left on the table with modern marine engines with factory tuning. Sure, adding a supercharger to a naturally aspirated engine would add a substantial amount of power, and a tune would be needed obviously, but if we are just talking about tuning alone I don't see how there would be much to gain over stock. Naturally aspirated gas engines are not easily improved from tuning alone. What would be changed exactly? Air fuel ratios on factory tuning are extremely close to ideal, and leaning them out at all would make slightly more peak power perhaps, as would more aggressive ignition timing, but then you would need to use a higher octane fuel to keep some safety from detonation or preignition, and even then you would be accepting the risks associated with a more aggressive tune. And I really think we would only be talking about a 5%ish gain at the absolute most with tuning alone. 20 extra horsepower at 5600rpm is not really helpful in a boat. The extra 140ft-lbs of torque at 3800rpm the LT4 gives over the M6? Completely different story.

 

[dizzygti]

14 minutes ago, DRB10SEVEN said:

It would depend on how much power is actually left on the table with modern marine engines with factory tuning. Sure, adding a supercharger to a naturally aspirated engine would add a substantial amount of power, and a tune would be needed obviously, but if we are just talking about tuning alone I don't see how there would be much to gain over stock. Naturally aspirated gas engines are not easily improved from tuning alone. What would be changed exactly? Air fuel ratios on factory tuning are extremely close to ideal, and leaning them out at all would make slightly more peak power perhaps, as would more aggressive ignition timing, but then you would need to use a higher octane fuel to keep some safety from detonation or preignition, and even then you would be accepting the risks associated with a more aggressive tune. And I really think we would only be talking about a 5%ish gain at the absolute most with tuning alone. 20 extra horsepower at 5600rpm is not really helpful in a boat. The extra 140ft-lbs of torque at 3800rpm the LT4 gives over the M6? Completely different story.

 

And all that applies whether it's a car or boat engine.   I would wager there was some cam phasing adjustments that could increase low end torque, which would be the main benefit possible.   Would it be a mind blowing change?  No.   Is a change with benefit still a change?  Yes.   OEM tuning in cars leaves a lot of compromises, I'm sure these engines are no different.   Cars also don't run water cooled exhausts which should offer some safety margin over an ambient cooled exhaust shoved in a transmission tunnel.  I run 93 in my M6 so octane is there for gains over the standard 87 R+M/2 programming.   

Edited February 29 by dizzygti

[DRB10SEVEN]

9 minutes ago, dizzygti said:

And all that applies whether it's a car or boat engine.   I would wager there was some cam phasing adjustments that could increase low end torque, which would be the main benefit possible.   Would it be a mind blowing change?  No.   Is a change with benefit still a change?  Yes.   OEM tuning in cars leaves a lot of compromises, I'm sure these engines are no different.   Cars also don't run water cooled exhausts which should offer some safety margin over an ambient cooled exhaust shoved in a transmission tunnel.  I run 93 in my M6 so octane is there for gains over the standard 87 R+M/2 programming.   

Hey, if you can squeeze a little more power out of an M6 with custom tuning for 93 octane fuel, that would be sweet. I was just giving the argument why most people would think it is not worth the effort for a minor improvement, which is also why I don't think there is a market for custom boat tuning.

[shawndoggy]

My experience with Md6i between 1900' and 5900' in a 21 A24 (which should be a reasonable albeit somewhat lighter proxy for 25er):

Prop: 17x15.5 / crew 3-5 adults in the boat / 400 lead in walkway or bow

2000': power for days / no issues / kinda wish for a 17x17 prop for a bit more top end.

4000' (where we do 90% of our boating): never wanted for power, never hit the wall.  Revs are definitely high (4k) if running a lot of wedge (4+).  Big change from my last boat, which was always at the limit here.

5500': can definitely feel the boat is "extended," but with a light crew still no problem hitting surf speeds.

5900': definitely hit the wall here last year and had to dump a little rear ballast to make it to surf speed.  I have a 17x14 prop as my spare and will definitely change it out the next time we go here.

Would I like the LT4? Sure!  But the Md6i + 2:1 trans + 17" prop has a ton of holeshot and does a great job for wake activities.  The downside of the drivetrain geared this way is that top speed bouncing off the rev limiter is probably 33-34 and cruising below 4k rpms is 26ish.  If you have to cover a lot of open water quickly, the LT4's higher trans ratio and ability to push a taller prop would really shine.  I know others have mentioned 50mph plus top speeds with the LT4.

For you with a heavier boat and bigger crew at slightly higher altitudes, I think I'd forego the 17x15.5 and run the 17x14 all the time. Which is gonna make the boat even slower, surf at higher rpms, and cruise slower.  But it should still be able to pull down a house.

[COOP]

20 hours ago, dizzygti said:

I'll be out of engine warranty after 2 years.   Care to explain in any more details?    I'm a powertrain engineer so understand elevated load and EGT's being affected by cam and ignition phasing, and that boats don't have multiple gear transmissions or grade/incline benefits here....but there is obviously power to be had on the table with adjustments.  Why is this so uncommon in the boating world?   

Its uncommon in MOST of the marine world.

There are some places that build "hot rod" engines and stuff, but very few. And most focus on go fast boats.

Im not an engineer, but I think alot of it has to do with the fact that many of the modern ECMs are locked by the manufacture, Indmar, PCM, Mercury, ect. Many of the Merc outboards are the same block with different tunes to give more horsepower. But Mercury will not give out the software to allow anyone to change them. Its kinda like phones, early smart phones were easy to jailbreak, root, but the newest phones are difficult if not impossible to do this to.

 

But I could be completely wrong, Im just a peeon.

[rennis]

On 2/29/2024 at 6:14 AM, dizzygti said:

Does anyone tune these engines period?   

A junkyard 5.3 with a coupl'a chinese whirly boys would make that LT4 look anemic.  

okay that's a joke but if it wasn't for the heat issue it turbos would be awesome for making power in a wake boat. One that would also overcome the altitude problem. 

[dizzygti]

9 minutes ago, rennis said:

 if it wasn't for the heat issue 

Just need to vent that bay and install some AWIC's!   

[DRB10SEVEN]

20 minutes ago, rennis said:

A junkyard 5.3 with a coupl'a chinese whirly boys would make that LT4 look anemic.  

okay that's a joke but if it wasn't for the heat issue it turbos would be awesome for making power in a wake boat. One that would also overcome the altitude problem. 

5.3? Jeez put those spoolies on a REAL engine like the new 6.6 L8T engine. Or are you afraid to make REAL power?? (jokes obvi)

[RyanB]

2 hours ago, DRB10SEVEN said:

5.3? Jeez put those spoolies on a REAL engine like the new 6.6 L8T engine. Or are you afraid to make REAL power?? (jokes obvi)

Good lord. If you’re going to do something at least do it right. 
 

[DRB10SEVEN]

33 minutes ago, RyanB said:

Good lord. If you’re going to do something at least do it right. 
 

O

Ok all kidding aside, Whipple's new blowers look KILLER. That massive dual pass intercooler is sweet. My wife and I have been saving to put one on our Suburban. 

[rennis]

3 hours ago, DRB10SEVEN said:

5.3? Jeez put those spoolies on a REAL engine 

kind of a joke, kind of not.  junkyard 5.3s are legendary in drag racing.  they make unbelievable power for dirt cheap money (relatively speaking) when you stuff them with boost. 

[DRB10SEVEN]

8 minutes ago, rennis said:

kind of a joke, kind of not.  junkyard 5.3s are legendary in drag racing.  they make unbelievable power for dirt cheap money (relatively speaking) when you stuff them with boost. 

Oh for sure. I love iron block LS stuff! I put heads/cam/intake on a junkyard 6.0 LQ4 for my 04 Sierra after my 5.3 needed replaced.

[Woodski]

On 2/29/2024 at 9:14 AM, dizzygti said:

Does anyone tune these engines period?   

Short answer, no.  There is not enough of a market for engine tuning in the towed watersports market, people simply plunk down some $ for the vessel they want.  It's basically a handful of forum gearheads that have any interest in building / tuning etc.  Along with the fact the ECU's are all locked so difficult to pry open.  Add the fact the risk is higher to tune closer to ideal peak power with more potential failure modes (raw water pump, marina gas, etc.) particularly in the heavily loaded boats.  I classify the go fast boats a totally different market and customer although that supplier base does offer stuff to boost power levels.

[theloungelife]

I'll chime in as I sometimes ride Willard.  Mostly hit the mountain lakes (Rockport, Jordanelle, Echo etc).  My 22' A22 has the M6 and it is solid heavily ballasted at mountain elevation (6000').  I have the acme 3065 prop on too, which helps.  I can feel the extra power when I'm at Willard though.  Your boat's dry weight is 1100lbs heavier than mine.  But...  you can run a 17" prop.  I feel like for Willard you could get away with the m6 no problem.  Even Pineview isn't as high up as Jordanelle etc.  Worst case when the boat is loaded with people, you drop some ballast.  I've had similar debates as I have thought about going up to the A24.  Now if money is not a matter, LT4 all day.  If you're taking out a loan though, I think I would want to save the money.  The M engines are pretty solid.  I demo'd a 2021 A22 with the M5 at Deer Creek when I was looking.  Actually was able to get on plane decent with full PNP ballast and a 400lb bag in the nose.  I was impressed but decided to go M6 anyway.