Impressions of Merc's new 6.2L 350hp

[FastMarkA]

As many of you are probably aware, Mercruiser unveiled a few new engines last year, most likely in response to GM's sunsetting of its larger blocks in exchange for more economical offerings in its vehicles.

Of particular interest to me is the 6.2L 350hp: https://www.mercurymarine.com/en/us/engines/inboard-and-sterndrive/mercruiser/62l/

It almost seems like it has the potential to cannibalize the 8.2L 380hp -- there's a 350lb weight advantage to say nothing of its improved economics.

I've noticed Formula has started installing these, so I'm just curious if anybody has one and, if so, how they like them?

 

[toofast]

I bet they will be big winners, aren't these the same blocks used in Vettes for some time. I used to have a friend that swore this was the best platform for boats, and i'll be darned.

As long as they are tough enough, I can't wait to see over time how they perform! But no real world experience by me just yet.

 

[afratki]

Look like nice motors with good HP but I wonder how they'll feel in a heavy boat. I assume they don't have the torque of a 496.

 

[AllDodge]

In the old days we would take a 350, bore it out, install a 400 crank and wind up with a 383 stroker. The Merc 6.2 is a 5.7 with a virgin bore (4.00) and a 3.75 stroke, which equals 377 cu in or 6.17L. If the block is ever bored .030 over it turns into a 383 cu in or 6.27L.

The 6.2 motor is great for light to medium weight boats, and produces more torque then the 5.7, but not as much as the 8.2.

The old saying still holds true, there is no replacement for displacement

 

[FastMarkA]

Formula shared some data with me on the 350 CBR (both boats had hardtops; the 6.2L had about 50 fewer gallons of fuel during its test):

At least on paper, the numbers are impressive, especially the range that the 6.2s offer.

Speeds are averages of two passes, so it's a relatively trustworthy test.

 

[AllDodge]

Guess I'll have a bit of trouble with the numbers. Merc 6.2L at 862 pounds, 8.2L weight 1122 pounds for 520 pound difference. Did find that the Ilmor weight was at 813 pounds due to aluminum engine (613 pound difference).

http://www.ilmor.com/en/marine/recreational/MV8-62L-OPS.aspx

Boattest did a review of the boat and it had 6.2L 430 HP Ilmor engine and drives and did better then the what your showing for the 8.2L. So add 600 pounds to a 14300 boat, and use a 8.2 430 hp or 6.2 430 hp motor the side by side test should be close.

http://www.boattest.com/review/formula/3502_350-fx-cbr

RPM	MPH	Knots	GPH	MPG	NMPG	Stat. Mile	NM	dBa
650	3.7	3.2	1.5	2.4	2.1	372	323.2	59
1000	6.1	5.3	2.8	2.2	1.9	342	297.5	66
1500	8.1	7.0	5.3	1.5	1.3	237	206.4	72
2000	9.3	8.1	10.4	0.9	0.8	138	120.4	75
2500	13.4	11.7	15.4	0.9	0.8	135	117.1	80
3000	22.3	19.4	19.6	1.1	1.0	177	153.5	81
3500	30.8	26.7	24.5	1.3	1.1	195	169.3	82
4000	36.0	31.3	31.2	1.2	1.0	179	155.6	87
4500	42.0	36.5	38.5	1.1	0.9	169	146.7	85
5000	46.5	40.4	51.8	0.9	0.8	139	120.8	89
5500	50.6	44.0	64.7	0.8	0.7	121	105.3	91
5680	56.0	48.7	66.5	0.8	0.7	130	113.3	90

 

[toofast]

So it is not all pure weight vs. pure HP...If I remember my GM engineer ex friend used to spout the 6.2 had quite a large sweet spot, but hey this is all third party guessing....Formula rarely screws up the tests...we need real world numbers

Honestly the 350 numbers on the 8.2 seem low to me, meaning I've tested extensively my setup and I get a bit more MPG, around 1.1 vs the .8 as tested. I think the 350 design should be more efficient that my PC as well.

Oh well...only time will tell!

 

[FastMarkA]

Following up on this with a day or so of real world experience.

The delivery captain had to do a high speed test (WOT) as part of Formula's commissioning checklist, and the boat hit 51 mph with gear, one person, full canvas enclosure up, and about 3/4 full tanks.

I'm extremely happy with those results considering the 8.2L HO 430hp only gets 4-5mph more with WOT speeds of 56mph. The 380hp 8.2L option presumably falls somewhere in between.

I did a 41 mile journey and burned 35 gallons of fuel (although that was hardly representative of real world cruising as I was switching up the RPMs every few minutes per break-in recommendations, anywhere between 1500 RPM and 4000 RPM).

These 6.2s have a throaty deep sound, and when put into gear, there is almost a diesel-like "jerk" that lets you (and anybody standing up) know that the boat is now in motion. Even when at cruise and you want to throw on another 500 RPMs or so, the response is instant, detectible, and fast.

I'm looking forward to getting more acclimated with these engines throughout the summer, but as of right now, I'm extremely happy with my decision to get these versus the 380hp 8.2s given the fuel and weight savings, additional range, and negligible (if any at all) performance loss. (The 430hp HOs, while fun, were never really a consideration for me at a $30k premium.)

 

[HellRaZoR004]

Nice results. What boat? Can't seem to clearly determine this from the thread.

 

[FastMarkA]

It's the 350 CBR.

 

[Jshell]

Looking forward to seeing how these engines perform in my 330 CBR when I get it later this month.

 

[FastMarkA]

Looking forward to seeing how these engines perform in my 330 CBR when I get it later this month.

With a slightly skinnier beam and a few less pounds than the 350, I'm guessing you'll be well into the 52-53 mph range WOT.

I believe BoatTest.com got the 330 w/ 8.2 380hps to 54mph WOT. Of course, those engines add 500-600lbs of weight.

Congrats on your 330 -- I'm curious to hear the results as well!

 

[Jshell]

With a slightly skinnier beam and a few less pounds than the 350, I'm guessing you'll be well into the 52-53 mph range WOT.

I believe BoatTest.com got the 330 w/ 8.2 380hps to 54mph WOT. Of course, those engines add 500-600lbs of weight.

Congrats on your 330 -- I'm curious to hear the results as well!

You might be right. Time will tell. Glad to hear they are performing well for you.

 

[Jshell]

Here is the "book" on the 330 CBR.

 

[FastMarkA]

Here is the "book" on the 330 CBR.

Those are nice conservative ranges so Formula isn't held to anything. With my 350 weighing an extra 1,000 pounds while also carrying a generator and hitting 51, I think we've already disproven the quoted 47-50 for the 330. What little money I have left is on 53mph for you/the 330.

 

[FastMarkA]

Here's some data I've collected with these 6.2s on the 350CBR...mostly from a Lake Michigan crossing. (Pardon my perverse obsession with data.)

Fuel (gal)

Water (gal)

Gear/Pax Weight (lbs)

Est. Total Weight (lbs)

RPM

MPH

GPH

MPG

Range (155 gal)

Range (162 gal)

75	30	500	14,947	820	4.7	2.8	1.68	260.18	271.93
74	30	500	14,940	1820	9.4	7.48	1.26	194.79	203.58
71	30	500	14,922	3230	24	19.42	1.24	191.56	200.21
70	30	500	14,916	2880	18	16.64	1.08	167.67	175.24
70	30	500	14,916	3320	25	20.6	1.21	188.11	196.60
68	30	500	14,904	3940	32.8	27.6	1.19	184.20	192.52
65	30	500	14,886	3500	27.6	22.11	1.25	193.49	202.23
64	30	500	14,879	3670	29.8	24.28	1.23	190.24	198.83
172	30	500	15,538	1390	8.1	5.32	1.52	236.00	246.65
172	30	500	15,538	3790	31	25.35	1.22	189.55	198.11
172	30	500	15,538	3250	22.8	19.87	1.15	177.86	185.89
172	30	500	15,538	3050	20.1	18.26	1.10	170.62	178.32
172	30	500	15,538	3030	20.2	17.91	1.13	174.82	182.71
172	30	500	15,538	3640	28.9	24.04	1.20	186.34	194.75
172	30	500	15,538	3660	29	24.06	1.21	186.82	195.26
156	30	500	15,441	3200	22.7	18.98	1.20	185.38	193.75
141	30	500	15,349	3210	21.8	19.54	1.12	172.93	180.74
141	30	500	15,349	3560	27.7	22.57	1.23	190.23	198.82
141	30	500	15,349	3890	32.1	27.23	1.18	182.72	190.97
141	30	500	15,349	3870	31.7	27.27	1.16	180.18	188.32
134	30	500	15,306	3600	29	23.04	1.26	195.10	203.91
141	30	500	15,349	4290	35.5	36.56	0.97	150.51	157.30
141	30	500	15,349	4300	36.1	35.87	1.01	155.99	163.04
141	30	500	15,349	4280	35.9	34.89	1.03	159.49	166.69
141	30	500	15,349	3720	30.2	24.99	1.21	187.31	195.77
141	30	500	15,349	3900	31.5	27.32	1.15	178.72	186.79
132	30	500	15,294	3630	29.3	23.43	1.25	193.83	202.59

 

[FastMarkA]

Just another data point to add to this thread...

With about 90 gallons of fuel, 5 people with overnight bags, and 2 cases of wine, at 3580 RPM we had a speed of 29.6 mph and fuel burn of 23.24 gph/1.25 mpg.

 

[Jshell]

Due to bad weather and too much floating wood on the lake, we haven't been able to do a lot of running. However, on our sea trial day we did see 52 mph during a brief speed run. This past weekend we cruised mostly 28-30 mph when it was safe to do so. Vessel view showed about 19 gph & 1.4 mpg at those speeds. Very happy with the engines so far.

 

[toofast]

Yeah that's phenomenal for those injuns my 496 is were nowhere near as efficient...
Nor as fast

Sent from my SM-G920V using Tapatalk

 

[FastMarkA]

I've completed my first season with the 350CBR and its pair of "new" Merc 6.2L 350hps.

I'm a little obsessed with data, so for "fun" I have compiled a lengthy spreadsheet where I tracked rpm/speed/gph readings throughout the season. What I've attached here are averages based several data points collected within each RPM band.

Overall, I think these engines are more than adequate for the boat. I've never sea trialed a 350CBR with the 8.2/380hps (nor has any of the pleasure boating journalists based on my excessive scouring of the internet; they all seem to have reviewed the boat with the 8.2 HO/430hps), but it would be interesting to compare the differences. (The 430hps give a top end of 56mph, FWIW.)

If I were building the boat again, I don't know that I'd find value in the $30k premium for the 8.2HOs. I'd actually be more willing to shell out for a diesel engine, if the option were available.

There were several times where I loaded the boat up with 12-16 adults (including their adult beverages and food for the day), and there were never any challenges with getting on plane. On one particular instance, I recall being challenged to hit WOT with 13 people on board, and we managed to achieve 48 mph.

I noticed hull growth has a significant impact on performance at all RPMs. I have a diver clean it every 2 weeks, and by the end of the 2nd week, I lose a mph or two at most RPM bands.