Performance of 390EC, 460EC, 350/370EC

J

JAndrewG

Member
Jul 23, 2007
158
Brownsville Washington (Seattle area)
Boat Info
340EC
Engines
330 HP Mercruiser inboards
For years I've talked to different owners of the above model Sea Rays from the mid 80's to mid 90's, and got varying and sometimes conflicting info on their performance. Some of this might be due to one person's 'cruise' RPM of 3600, where another would consider 3100-3200 a better engine speed at 'cruise' (I'm in this group) for 7.4 gas motors.

So those of you who have had or still own one of the above models, can you give us some real numbers, including speed at a given RPM and fuel burn? I'd love to know the real difference between a 390EC with gas or diesel, the difference in the 460EC with the smaller 3208TA's and the 450/550 hp Detroits, and how the 350/370DA or EC compares.

It would also be interesting to know how many RPM is needed for any of these to stay on plane. Does a 390 need to run 3500-3600, or can it be pulled back to 3000 RPM and stay up with a little trim tab?

Frank W, I saw you post recently that you once owned a gas '88 390EC...any input?

Thanks guys, I'll look forward to hearing from you.
 
My 370 had 7.4s and I cruised at 3550 rpms. With full fuel and water the boat did 22-23 knots until the boat lighten up due to fuel burn. I began to pull the throttles back as she lightened up and would do 24-26 knots at 3500. NMG was .5 to .65 depending on sea conditions. I cruise with a 390 owner and he does about 19 miles per hour at 3500. Not sure what his fuel burn is although he has a pretty short range and is buying gas every 125 miles.
 
I had a 1989 460EC witht the 3208TA's and it ran about 22/23knts at 2400rpm
btw, that was a great boat! I am pretty sure it was slower than the detroit boats but it didn't feel slow at all. It accellerated and handled very well since there were no V-drives.
I would reccomend that boat to anyone. I loved mine.
 
sbw1 said:
My 370 had 7.4s and I cruised at 3550 rpms. With full fuel and water the boat did 22-23 knots until the boat lighten up due to fuel burn. I began to pull the throttles back as she lightened up and would do 24-26 knots at 3500. NMG was .5 to .65 depending on sea conditions. I cruise with a 390 owner and he does about 19 miles per hour at 3500. Not sure what his fuel burn is although he has a pretty short range and is buying gas every 125 miles.
Click to expand...

sbw1, your 370 was a Sundancer? Did it take 3500 RPM to stay on plane, or was that more an optimum speed for mileage? 22kts / 25 mph is a good speed.
 
geriksen said:
I had a 1989 460EC witht the 3208TA's and it ran about 22/23knts at 2400rpm
btw, that was a great boat! I am pretty sure it was slower than the detroit boats but it didn't feel slow at all. It accellerated and handled very well since there were no V-drives.
I would reccomend that boat to anyone. I loved mine.
Click to expand...

geriksen, that's faster than I would've thought. Thanks for the info. What is the recommended WOT for the 3208TA's? Would it plane slower?

I've never ridden in a 460EC, but 'raced' one once with my 300WE. As I approached him I saw him looking my way and I motioned to firewall the throttles. He did, then I did, and I barely was able to pass him. My 300WE did maybe 33kts or slightly better. I was really impressed, and found out later that his had the 550 Detroits.
 
JAndrewG said:
sbw1, your 370 was a Sundancer? Did it take 3500 RPM to stay on plane, or was that more an optimum speed for mileage? 22kts / 25 mph is a good speed.
Click to expand...

Nope, the boat was an express. It's been a while but she would stay on plane down to around 2600-2700 rpms if memory serves. That was not effecient, but in sloppy seas was about the best you could do and make reasonable time. 3500 felt pretty good and was the most effecient for cruising. The 37 is a pretty fast boat.
 
sbw1 said:
Nope, the boat was an express. It's been a while but she would stay on plane down to around 2600-2700 rpms if memory serves. That was not effecient, but in sloppy seas was about the best you could do and make reasonable time. 3500 felt pretty good and was the most effecient for cruising. The 37 is a pretty fast boat.
Click to expand...

That's just the kind of first hand info I'm looking for. It's a very good thing to be able to pull back when the water bucks up, and not have the bow so far in the air that you can't see anything. I have always liked the early 370EC. It sounds like it handles pretty well, and you're right- fast too.

Thanks.
 
John-
My 390 has the 355 hp 3208 CATS; to my knowledge they were available up to 425 hp (others can correct if I'm wrong here) which will make a difference in performance. I'm happy with the performance at that level, the "hopped-up" versions don't last as long between overhauls I'm told. At 2400 rpm my cruise is 21-22 kts depending on fuel load, haven't actually checked speed at WOT (2800). I don't have Flo-Scans, but I'm told that 12 gph or so per engine should be about right at that rpm for right around 1 nmpg.

Remember too, that the CATS are very heavy. Sea Ray did not list the weight for the boat with them, but I'm sure the diesel version must weigh at least a ton more (1000 lbs/side)than the gas.

I'm returning from a ski vaca tomorrow and will post the pics of the 390 I promised...
 
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