End of the Volvo big block motors......

[Scott Danforth]

Re: End of the Volvo big block motors......

Mercruiser and volvo (along with PCM and many others) bought a crap load of 8.1's (496 cu in) in 2008 and has been working on inventory since then. Since Mercruiser sells over 10 times the engines that anyone else does they ran out first.

GM discontinued the 8.1 for industrial use in 2009 and cam out with marinized versions of the LSX's (both the 6.0 and 6.2sc). the 6.2sc is used in the Seven Marine 557's.

Mercruiser took their 525 8.2 liter (502 cu in) and de-tuned it for the 425 duty because it was less expensive to do than buy the 6.0 LS motor from GM.

if you have a new boat with a 8.1, look at the casting date of the block, its actually old inventory. The good news is that the warranty starts at date of service and not date of manufacture.

 

[FormulaFanMN]

Re: End of the Volvo big block motors......

Merc didn't buy up supply of the 8.1. Volvo did. Volvo ran out and their only option was the 6.0.

Time will tell how this all shakes out, but have a very strong feeling Merc is going to do fantastic.

This engine is not a big block replacement.

All the videos, press releases, etc can make this new engine look good on paper. The 2.14 gear ratio isn't special to this. The 5.7 uses it. The exhaust manifolds are closed cooled....great, but they're all closed cooled on ocean x products.

Granted, some features are nice, but certain boats need low end torque and this engine doesn't have it. Granted, it produces 6000 rpm and 380 horsepower, but so does the Merc at 4800 rpm.

Why choose an engine that you cruising at 4000 RPMs or higher vs an engine that you can cruise at 3500 rpm.

Ask a Volvo rep at a boat show how volvo is dealing with an engine that produces over 100 lb-ft less of torque vs the Merc? You can talk about weight savings, etc , but torque is what get a heavy boat on plane not horsepower.

This new engine produces the same torque at 3200 rpm vs the 5.7 and only produces 30 lb-ft more than the 5.7 at a whopping 4400 rpm.

 

[QC]

Re: End of the Volvo big block motors......

Then I guess the only answer for you is don't buy it. I will repeat though, unless the throttles are 100% mashed you aren't using peak torque anyway, but all good

 

[QC]

Re: End of the Volvo big block motors......

And you know . . . if you run the gear ratio down (higher numeric) that propshaft torque goes up and may in fact match the 8.1 and even it's propshaft speed. And then once wound up could be very close to the same output shaft speed. Yes, RPM means that stuff may be wearing faster, but if the wearing stuff is higher quality then . . . Point is we don't have longevity data, so hard to comment. This may be only an ear issue (high rev sound) and nothing else. Checking the numbers now.

 

[bruceb58]

Re: End of the Volvo big block motors......

Seems to me the only way that we are going to be able to use these engines that have peak torque at higher RPMs is to go with multi speed transmissions.

 

[QC]

Re: End of the Volvo big block motors......

Let's make this simple. Let's say we have an engine with 450 lb. ft. at 4000 RPM, and one with 600 lb ft. at 3000 RPM. The first setup is run through a 2:1 ratio, and the second a 1.5:1. Which one has more torque at the propshaft? And at what propshaft RPM is this peak torque developed? What horsepower do they develop at this peak torque RPM? And with the same propset what theoretical speed would both theoretical boats be running if all else was equal? What if one of them was lighter, and now not equal?

 

[bruceb58]

Re: End of the Volvo big block motors......

I will play.

The peak torque will be developed at the same propshaft RPM. Both would have identical HP and both would be running the same speed at that particular propshaft RPM.

 

[QC]

Re: End of the Volvo big block motors......

Right. 900 lb/ft torque at the propshaft at 2000 RPM, which is 342 HP at that same 2000 RPM and with the same propset (DP) they would be going the exact same speed because both would support exactly the same load at the same RPM and power. Annnnnd . . . theoretically the lighter example would be slightly faster as it's load would be slightly less.

Ok so move to the 6.0. Why can't a higher revving engine do the same work then? Yes all theoretical, and all paper, but unless someone is writing the numbers down wrong (torque, RPM, gear ratio) or someone is not testing the examples properly (dynos) or someone is lying, then why don't the paper examples translate to real world? They actually do if the data is right. So for me, this comes down to three variables (probably more when I think about it). Durability (yet to be known), the sound of higher RPM (maybe sweet), and fuel efficiency (may be the same or could favor either example, need field data). Everything else is emotional. Oh yeah, and the new example is lighter.

Yes, I know the real numbers are not the same as my example, but I used those to make the point. We can't simply sit hear and say that the smaller displacement example won't do the job. My 6.2 320 will outrun a 7.4 310. Period. And a 260 MPI 5.0 will spank an old "260" (it was only around 230 at propshaft). And an OB outruns an I/O of the same HP, lighter and higher RPM. Hey wait, why isn't that example validation?

 

[bruceb58]

Re: End of the Volvo big block motors......

Except that you are now close to the max engine RPM of the smaller engine and the bigger displaceemt engine has another 1000 RPM to go so your max speed is going to be a lot lower with the lower displacement engine. This of course assumes that the max engine RPM is about the same for the two engines which is probably true in real life.

 

[QC]

Re: End of the Volvo big block motors......

No, they are way apart and why I mention that durability becomes one of the issues. The 6.0's peak at 5600 RPM.

http://gmpowertrain.com/MarineEnginesControllers/ProductPortfolio.aspx

 

[bruceb58]

Re: End of the Volvo big block motors......

Yeah you are right. Didn't know that about the 6.0.

So let's say the bigger block has a peak RPM of 4800 which is what the 5.7 currently has, the big block will have an extra 1200 prop RPM left before hitting its max at 4800 engine RPM. The smaller engine has an additional 2600 engine RPM so additional 1300 Prop RPM.

I do see your point.

 

[QC]

Re: End of the Volvo big block motors......

Yeah, and other than climbing the bow wave (big deal), prop load curves are linear, so the belief that marine requires a big torque peak down low, is sort of false. Not completely, and it is variable by hull design, weight etc. But the fact is, say in a full displacement hull (no climbing out), peak torque doesn't even come into play. These are all simple statements, and many other factors usually come into play. As some like to say "your mileage may vary". But the numbers pencil OK when you take out the initial emotional reactions.

 

[FormulaFanMN]

Re: End of the Volvo big block motors......

The WOT on the new Volvo is 6000 rpm. Not 5600.

Torque is what planes a boat not horsepower. Use a Volvo Penta D4-300 diesel for example. It's only 300 hp at 3500 rpm, but produces 518 lb-ft of torque at 2500 rpm. It also weighs over 200 lbs more for each engine and drive over an 8.2. Now for cruise, the diesel will cruise at the same speed as the gas 8.2 at 3000 rpm.

Engine torque is engine torque. If the new engine is only capable of producing 400 lb-ft at 4400 rpm.

Use an example of twin 6.2 Mercs in a Formula 350ss and compare it to the same boat with twin 8.2. The 6.2 package will need to cruise over 600 Rpm higher to achieve the same mph and burn 1.5 gph less. Which one would a person want? I would rather cruise at 3500 rpm compared to 4100.

My biggest complaint with Volvo on all the Press release literate is they never mention cruise rpm when showing the numbers.

In the old Volvo 8.1, they used a 1.78 ratio and Merc uses a 2.0 with the current 8.2. The 2.14 is spinning fast and time will tell how much more strain it's placing on the drive??

 

[FormulaFanMN]

Re: End of the Volvo big block motors......

Peak torque also comes in play every single time you plane your boat. That's why diesels are so phenomenal with the low end torque they produce.

 

[QC]

Re: End of the Volvo big block motors......

The WOT on the new Volvo is 6000 rpm. Not 5600.

Actually 5800.

Torque is what planes a boat not horsepower.

I can absolutely guarantee you that what torque does is make horsepower if you have even 1 RPM. You need to trust me on this. You are repeating stuff that the Auto and Truck market have ruined for the world of truth. Good high peak torque values, whether from a diesel, turbine, steam engine, whatever, makes horsepower. And horsepower does the work at a rate that is acceptable, time matters, whether it is planing the boat or cruising or running WOT. Yes, an engine with more torque at the same RPM will plane a boat better, but it is because it produces more horsepower at that point. Your diesel example is perfect if you carry it out to the rated power. The 6.0 will be faster. Period. It makes more power (horsepower by developing some torque at WOT).

Engine torque is engine torque.

Without RPM it is a worthless number. With RPM it makes horsepower. Bears repeating

I would rather cruise at 3500 rpm compared to 4100.

OK.

My biggest complaint with Volvo on all the Press release literate is they never mention cruise rpm when showing the numbers.

Why would they? They would like to sell engines

In the old Volvo 8.1, they used a 1.78 ratio and Merc uses a 2.0 with the current 8.2. The 2.14 is spinning fast and time will tell how much more strain it's placing on the drive??

The 2.14 will equalize input torque, so it should be fine.

Peak torque also comes in play every single time you plane your boat. That's why diesels are so phenomenal with the low end torque they produce.

Not true. Peak torque only comes into play if the throttles are mashed 100%. This is a fact unless you are climbing a hill in a wheeled vehicle with a full range governor, then the engine will apply full fuel on it's own. In marine, only with throttles jammed to the wall.

I am still not sure what you want? Maybe you want Volvo to design an entirely new big block V8 gasoline engine for marine pleasure-craft. That would be incredibly stupid as their unit volume would never pay it back . . .

I fight this fight a lot, and some here I am sure would prefer I just button my lip, but the fact is I have done nothing but sell high torque rise diesel and natural gas engines for the last 34 years. Nothing. I spec trucks for a living. I guarantee I know what torque does, and what it doesn't

 

[FormulaFanMN]

Re: End of the Volvo big block motors......

Per Volvo product data sheet I received from Volvo itself, WOT is 6000

Obviously we see differently on this. I will report back when I get a chance to test these engines on a formula 34pc from volvo penta and compare it to the boat i owned with the twin 8.1.

 

[QC]

Re: End of the Volvo big block motors......

Which 8.1s?

 

[FormulaFanMN]

Re: End of the Volvo big block motors......

Twin Merc 496 Mag (375hp) with DTS.

 

[QC]

Re: End of the Volvo big block motors......

What gear ratio are those?

 

[QC]

Re: End of the Volvo big block motors......

For FFM:

If I assume (bear with me here), a 1.68 ratio for the 8.1 and a 2.14 for the 6.0, here are the propshaft torque, horsepower and RPM for the both. I understand your drive longevity concerns, and I understand your RPM concerns, but lets just talk about performance potential on paper for right now. Need that one out of the way.

8.1) 503 lb.ft x 1.68 ratio equals 845 lb ft. at 1904 RPM (1904 is 3200/1.68) The horsepower at that point is 845 x 1904/5252 = 306 shp (shaft horsepower) It still makes it's 380 hp at the top but the shaft is turning 2738 RPM.

6.0) 400 lb ft. x 2.14 ratio equals 856 lb ft. at 2056 RPM (2056 is 4400/2.14) The horsepower at that point is 856 x 2056/5252 = 335 shp It still makes it's 380 hp at the top but the shaft is turning 2803 RPM.

These are your numbers on the 6000 RPM, 4600 RPM, and peak torque of 400 at 4400 RPM, and 503 at 3200 respectively for the 6.0 and 8.1. Your boat only cares what is happening at the shaft. Your ear, and maybe wear care differently, but neither may be "worse". And of course, all of this only matters in use. I get that. But the numbers alone do not crucify the 6.0, and that has been my point from the beginning.

Edit: Ooops, I should've used your Merc numbers. I used Volvo for both . . . point is the same. If I get bored later I'll recrunch.