PCM H5 vs Excalibur 343?

[NautiqueJeff]

You do have to be registered there to view it. I had that issue too until I logged in there.

[scottb7]

Here is the pic. But what I would like to see is the comparable math. What is the ? number? (Don't back into it, provide number and backup from pcm)

ex343 = 430/1.23 = 350 crank ft lbs
H5 = ? / 2.0 = 405 crank ft lbs

[Wayward]

Here is the pic. But what I would like to see is the comparable math. What is the ? number? (Don't back into it, provide number and backup from pcm)



ex343 = 430/1.23 = 350 crank ft lbs
H5 = ? / 2.0 = 405 crank ft lbs

The ? Would equal 810lbft at the prop shaft. It is 405 x 2.0.....

The 343 numbers are derived from the 350lbft of crankshaft torque multiplied by the gear reduction of 1.23:1, which equals 430lbft of propshaft torque.

Neither figure set accounts for parasitic drivetrain losses, which would reduce both prop torque numbers slightly. Not really any need to have PCM back up the propshaft torque number if they give the engine torque, and the gear ratio. There is no need for backup. It is a mathematical certainty.....

[scottb7]

Wayward, Do you really believe the ex343 puts out "350 crank ft" lbs as compared to the h5 which YOU are stating is putting out 810?

I doubt if there would be that much variance between the 2 engines.

[Wayward]

No....... You asked somebody to solve for the "?", which is the PROPSHAFT torque in the equation. The "crank torque" is stated as 405lbft (which, yes, I believe it is likely that the H5 might actually produce 405lbft)

Now...... If it does, in fact, produce 405lbft, as advertised, and is then routed through a 2:1 gearbox.......... The propshaft torque will be 810lbft (minus a small amount for parasitic losses through the gearbox.

I don't have to believe anything. If the facts you gave are true, then my calculations are correct. I solved for "?", which was what you asked for.

[cedarcreek216]

I think he was asking for the manufacturer to provide the ? # and not ask us to back into it. Because backing into it would provide an unbelievable output number which is proven by the 810 lbft you got when you solved for the ?.


Sent from my iPhone using Tapatalk

[Wayward]

I think he was asking for the manufacturer to provide the ? # and not ask us to back into it. Because backing into it would provide an unbelievable output number which is proven by the 810 lbft you got when you solved for the ?.


Sent from my iPhone using Tapatalk

I guess I am at a loss here......... So, let me ask this- Is everyone in agreement that PCM advertises the H5 as having 405lbft of torque at the crank?? (Visiting their website confirms this)

It does not matter if PCM advertises the propshaft torque or not. There is but ONE SINGLE WAY to calculate output/prop shaft torque. If they advertised it as anything but 810lbft with a 2:1 transmission, they would look very stupid........

I didn't "back in to it".
810lbft is not at all unbelievable
There is only one answer to the question, no matter if I say so, or PCM does.

If you want to calculate output shaft torque, the only way to do so, is to take your input shaft torque and multiply by your gear ratio. That simple calculation gives you your output shaft torque.

For instance, if you swap around the engine or trans, this is what happens.....

H5 with 1.23:1 transmission would have 498lbft of propshaft torque.
Ex343 with a 2:1 transmission would have 700lbft of propshaft torque.

[Beach-TJ]

JC, one thing to note is the H5 (5.3) is going to be a different beast in the 210 than in a G. Looking at the Nautique site, the H5 gets the 2:1 reduction V-Drive in the G's, but only the 1.48:1 reduction V-Drive when in the 210. The 2:1 reduction is going to really help the H5 in the G's, and make it pull a lot harder than in the 210 with only 1.48:1. When you think about it a 2:1 reduction is just over twice the gearing as the 1.48:1.

When comparing engines for wakeboarding I prefer to look at the TQ curve and what power is delivered at the RPMs I will be using the engine. I find peek HP and TQ numbers are generally at RPMs that are so high they do me no good. The GM V8's generally have a max cruise around 3,800 to 4,000 rpms, and I normally operate my boat below these RPMs, thought the peek HP and TQ for most blocks are above these RPMs. You can find the TQ curve's for all the GM blocks here to do your own comparison.

[Catalac]

when looking at the gm marine torque chart specs, looks like H5 makes about 345lbs at 2000rpm, 370 at 3000, 380, 4000. (Not sure how pcm gets it up to 405) The old 5.7 aka 343 makes 360lbs, 365lbs and 360lbs at same rpms. My take away H5 will have a great torque curve. I'd never order a G boat with the H5 but I definatley would with the H6. As previous posts cite the H5 in a 210 will have a very similar feel to the old 6.0 409.

[cedarcreek216]

It's very interesting and informative to read about the mathematics behind the options, but from a real world experience on the water in this hull, I just don't see a need for anything more in the 210 than the 343. Would the extra power be nice, sure, worth the additional cost, guess that's for the purchaser to decide.

As I stated, we have had a lot of ballast and people weight in ours with little trouble. The hull likes bow weight regardless of surfing or boarding so that makes it much easier for the motor to function when heavily weighted.


Sent from my iPhone using Tapatalk

[jc]

Thanks for all the feedback! When it really comes down to it the 343 is enough for any boat once they are on plane and cruising at speed, surfing, skiing or wake boarding fully loaded. The difference comes when it's time to punch the throttle, I have ridden behind G's, 230's and 210's and no matter what motor it's always full throttle out of the hole if running full ballast and passengers...so thats where the torque comes in. Any loaded boat is full ''pin'' on take off until set speed is reached and it looks like the H5 is the better choice IMO.

[cedarcreek216]

And there you have it. Sounds like you knew the answer from the start. We never have ours at WOT at take off or cruising, no need for it.


Sent from my iPhone using Tapatalk

[jc]

Definitely wasn't sure about the H5's ability, but the feedback helps. Our experience fully loaded with more than 6 people is a need for max throttle or close it to get on plane, my friends G23 with the 450 barely gets on plane loaded to capacity. Only been in 210's with the 409 which was more than enough loaded, no experience with the 343 or H5. Never cruise at more than 3/4 throttle either way, too much fuel!