osd9
New Member
Looks like from a fuel efficiency standpoint that you are about the same over the range from ~3200-3800 RPMs
Mercruiser 8.1 370 HP versus 420 HP
- Thread starter Pseudomind
- Start date
ChuckW
Active Member
- Mar 6, 2009
- 1,487
- Boat Info
- 2007 RoadKing Tri-Axle Trailer towed by a 2013 Yukon XL K2500
- Engines
- 496 MAG Bravo III
Correct... as the GPH goes up, the Speed goes up in equal ratio. Look at the power band curve earlier in the post, the 3-4k RPM range is right in the sweet spot for torque on this engine as well. It's all connected...:thumbsup:
keokie
Well-Known Member
- Dec 27, 2006
- 1,486
- Boat Info
- 2002 310 Sundancer, Westerbeke 4.5 Genset
- Engines
- 496's, Bravo III's, 2.2:1 Gears
A lot of stuff flying around.
Unless Merc changed something, the original Bravo III's were rated at 450hp and shipped with both 502's and 496 HO's.
The 8.1's are in fact full of car parts.... OK truck parts. The internals are from GM and are the same as in a pickup. Previously Merc would switch to forged components in the 454 Mag (385hp) and 502 Mag (415hp). The 496's and standard 454's have the same components (crankshaft, connecting rods, and pistons) as a pickup. I have heard conflicting information regarding the heads (from Mercruiser), but suspect they are the same.
Performance guys are not big on the 496's because bumping output via supercharger has a high tendency to break them. The 454 Mags and 502's could take supercharging very well. In fact Merc's 525 SC was just a supercharged 454 Mag.
As far as fuel consumption, the 496's will take about 14 GPH at 3200, if propped to reach 4800 at WOT. They'll draw 32ish at 4800.
Reading what I wrote so far, it sounds as if I don't like the 496's. I do. That was the reason I bought my 310. they are good motors. Smooth, quiet, good power, (exceptional midrange in the standard 496 which is great for a cruiser). The roller cam, 8 coil ignition, and 8 channel fuel injection really has a lot to do with the smoothness and midrange of the 496. But I prefer the toughness and simplicity of the 454 Mags and 502's. And of all the motors, the 502 did a great job of being strong throughout the entire RPM range.
Unless Merc changed something, the original Bravo III's were rated at 450hp and shipped with both 502's and 496 HO's.
The 8.1's are in fact full of car parts.... OK truck parts. The internals are from GM and are the same as in a pickup. Previously Merc would switch to forged components in the 454 Mag (385hp) and 502 Mag (415hp). The 496's and standard 454's have the same components (crankshaft, connecting rods, and pistons) as a pickup. I have heard conflicting information regarding the heads (from Mercruiser), but suspect they are the same.
Performance guys are not big on the 496's because bumping output via supercharger has a high tendency to break them. The 454 Mags and 502's could take supercharging very well. In fact Merc's 525 SC was just a supercharged 454 Mag.
As far as fuel consumption, the 496's will take about 14 GPH at 3200, if propped to reach 4800 at WOT. They'll draw 32ish at 4800.
Reading what I wrote so far, it sounds as if I don't like the 496's. I do. That was the reason I bought my 310. they are good motors. Smooth, quiet, good power, (exceptional midrange in the standard 496 which is great for a cruiser). The roller cam, 8 coil ignition, and 8 channel fuel injection really has a lot to do with the smoothness and midrange of the 496. But I prefer the toughness and simplicity of the 454 Mags and 502's. And of all the motors, the 502 did a great job of being strong throughout the entire RPM range.
highslice
Well-Known Member
- Mar 28, 2008
- 6,108
- Boat Info
- 270 SLX
2013 Sea Doo 155 Wake
- Engines
- 496 Mag
Bravo III
Corsa
We cruise at 3,200 RPM, which makes for a tick over 30 MPH on the GPS. Fuel burn is about 12.5 GPH for us. If I drop the hammer I can go from 30 MPH to 45 MPH at the drop of a hat. Midrange is awesome with the 496.
I was concerned about fuel burn on the 496 vs. our 350. but it turns out that we actually use less gas, unless I decide to open her up. IIRC the fuel burn on the 350 at WOT was right around 20 GPH vs. 32 GPH for the 496.
I was concerned about fuel burn on the 496 vs. our 350. but it turns out that we actually use less gas, unless I decide to open her up. IIRC the fuel burn on the 350 at WOT was right around 20 GPH vs. 32 GPH for the 496.
Woody
Well-Known Member
When I purchased my '04 270SD the HO upgrade required the B3X because the B3 max hp was 400hp. I don't know how long it had been that way but it is still that way now. B3=400 hp max, B3X=450hp max
Is this the same 502 that replaces the 496? I wouldn't want the catalytic converters though. Risers are costly enough. Can't wait to hear the first story about replacing a pair of catalytic converters.
rondds
Well-Known Member
- Oct 3, 2006
- 8,859
- Boat Info
- 2001 380DA
- Engines
- Merc 8.1s (2008)...Hurth ZF 63 V-drives...WB 7.0 BCGD (2013), Garmin 8208 & 740 MFDs, GMR 24xHD dome
Skuza
What speed are you making cruising at 3200rpm? TeamSeaRay - same question to you. 17800lbs sounds high for a 2000 340DA. Not nitpicking but if your boat is truly that heavy (dry), you're pushing the limits for "all day."
What speed are you making cruising at 3200rpm? TeamSeaRay - same question to you. 17800lbs sounds high for a 2000 340DA. Not nitpicking but if your boat is truly that heavy (dry), you're pushing the limits for "all day."
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Roger that, but the 496 was replaced with a 502. I wonder if the new 502 is that same basic architecture as the old 502 with ergonomic tweaks, software, and catalytic converters. If so, definitely a worthy successor of the 496, sans the catalytic converters.
Woody
Well-Known Member
I think I would call it a new engine. Auminum heads, changes in pistons and rings(the 502s of the past had oil use issues). http://www.brunswick.com/news/newsstories/release/1/1324095.php
Skuza
Well-Known Member
It's been a long winter but if memory serves me correct I'm thinking 3,200 gets me 22-24 knots (~24-26mph). The 400 dancer was reported to be 22,500lbs but wonder if that was with diesels?
osd9
New Member
I'd say the winter got the best of your memory....:grin:
Those numbers sounds a little aggressive to me....my 2002 380DA, with twin 370HP 8.1s, similar hull and lighter weight, would run:
RPM-----SPEED knots---GPH -------sMPG
3200------19.9---------25.3----------0.835
3300------20.2---------28.1----------0.826
3400------21.5---------28.5----------0.867
3500------22.9---------30.5----------0.866
3600------23.8---------31.9----------0.859
3700------24.8---------33.6----------0.848
3800------25.4---------36.1----------0.809
