Picking up my new (to me) Sea Ray 390 EC today!

wileecoyote said:
I'm glad the 340EC made the list, but I have to say the 390 is one of the nicest boats I've seen out of the Sea Rays. I actually looked at that boat a few weeks back while scanning the market for 390 diesels. Dockmate has a 390 with 7.4s, but the diesels are the only way to go. Congrats, the beam on that boat makes it seem like a good sized condo. We often hang out in the cockpit of our dockmate.
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Wilee...

FYI..340EC's are getting a bit of a cult following here in South Florida...sort of the '55 Chevy of the cruiser crowd. They are relatively inexpensive and there seems to be quite a few of them around.

A friend that builds marine engines outfitted one with twin 600 HP/700 Ft.Lb.TQ 540 Big Block Chevy's turning 25" 4 blade props through ZF HD transmissions with 2" prop shafts. The 340EC reportedly cruises at 45 MPH and tops out at 57~58 MPH at 4800 RPM.:thumbsup: I'm going to try and run this down and get pictures...stay tuned.

There is also talk of a 390EC with a pair of 450 HP Yanmar Diesels that I am trying to catch up with also...would make a good "Awesome Mods" thread.
 
Congratulations on the new boat.

Better be prepared for "the magnet effect" of that big cockpit. You'll make lots of new friends during raft ups. They'll all be hanging out on your boat before you can say "where's all my beer?"

Sincerely though, enjoy!
 
Mastry Engines in So Fla also repowered a 340EC with 230hp 4 cyl Yanmars a year or so ago. Nice installation, really opened up the engine spaces. She would cruise in the high 20's (mph) and run all day on $10 worth of diesel........but a gas to diesel conversion isn't for the faint of pocketbook. That one was in the $60K area..........on a $40K boat at the time. For the total investment, the owner could find a very nice SR with diesels already in it.
 
Nice Boat! Congratulations, like was mentioned already, that boat is a party magnet (ah, hm, don't ask how i know), I'd like to see them diesel's
 
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How in the world did they get those big wheels under that thing? I bet that thing will fly!
sprink56 said:
Wilee...

FYI..340EC's are getting a bit of a cult following here in South Florida...sort of the '55 Chevy of the cruiser crowd. They are relatively inexpensive and there seems to be quite a few of them around.

A friend that builds marine engines outfitted one with twin 600 HP/700 Ft.Lb.TQ 540 Big Block Chevy's turning 25" 4 blade props through ZF HD transmissions with 2" prop shafts. The 340EC reportedly cruises at 45 MPH and tops out at 57~58 MPH at 4800 RPM.:thumbsup: I'm going to try and run this down and get pictures...stay tuned.

There is also talk of a 390EC with a pair of 450 HP Yanmar Diesels that I am trying to catch up with also...would make a good "Awesome Mods" thread.
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Rule of thumb for gas engines: 10% of max hp = max fuel burn. 60 gph per engine @ wot...120 gph combined.
The 45 mph cruise would be sweet...
The 60 gph fuel burn...not so much.

Hope for his sake he never decides to sell it!
 
dantheman said:
Nice Boat! Congratulations, like was mentioned already, that boat is a party magnet (ah, hm, don't ask how i know), I'd like to see them diesel's
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Nice looking magayacht you have there, but you had back that thing off to 59' or so. Don't you need your Captain's Licence for anything over 60'? :smt043
 
tobnpr said:
Rule of thumb for gas engines: 10% of max hp = max fuel burn. 60 gph per engine @ wot...120 gph combined.
The 45 mph cruise would be sweet...
The 60 gph fuel burn...not so much.

Hope for his sake he never decides to sell it!
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Yeah...I here you. The owners' other ride is Cigarette 39 Top Gun Unlimited with Merc 850 SCi's ...so he's into some fuel consumption mentality. The reason he did the 34 was to have a sleeper to surprise the unsuspecting.:thumbsup:

He bought the 34 w/sad engines for $10K and spent $50K bringing it back. He would do well to get half of that back selling it.

Mike...you know how these guys are that have the kind of money it takes to do this stuff....it's all about the ego. Like my engine friend said..."There's no recession in the go fast boat business". These are the guys that normally are developing property that guys like us get paid to build for them. There is no return from that now so they are making money investing overseas...and spending it on toys.:huh:

They don't think like we do.

John F
 
I'll bet somebody named Brandon is crawling all over a 390EC today...polishing, cleaning and smiling.:thumbsup:
 
Thanks for all the comments and replies. Yes, it was a very long weekend of cleaning, organizing, and creating a to-do list about a mile long.

One question for those that own the same boat, what is your top speed? At 2800 rpm (I believe CAT's recommended max), my throttles are only 3/4 of the way to the stops and the boat is running at about 25 mph. Is this right? This is with 1/4 tank gas, full water, and 4 people aboard with the trim tabs nearly completely down.

Thanks again.
 
Seems kind of slow... Last time I checked speed with clean hull, flat sea, mine did 29.5 kts (33, mph) with full tank and 2 people. Now without all the water I was carrying under the cabin floor I'm expecting more :smt001

Was your hull clean??? My 390 is very sensitive to fouling...

BTW ...I have 21"x24" 4 blade props :wink:
 
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bw219 said:
Thanks for all the comments and replies. Yes, it was a very long weekend of cleaning, organizing, and creating a to-do list about a mile long.

One question for those that own the same boat, what is your top speed? At 2800 rpm (I believe CAT's recommended max), my throttles are only 3/4 of the way to the stops and the boat is running at about 25 mph. Is this right? This is with 1/4 tank gas, full water, and 4 people aboard with the trim tabs nearly completely down.

Thanks again.
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Sounds like you might be a bit under propped. For comparison, my 390 with MPI 7.4 gassers would run 28 kts (about 33 mph) with a clean bottom and 3/4 tank with 4 on board. I think yours will top at about 32 kts (36 mph) with everything right....and use a lot less fuel:thumbsup:

Are you sure your GPS was reading MPH and not KTs? Most Garmins default to kts/hr. Worth a look.
 
Thanks for the replies. Yep, I've got a mph readout on the GPS and a knots readout on the depth sounder. I thought 26 seemed way too slow.

I've got three bladed props and the bottom is perfectly clean. I figured it was under propped. Unfortunately, no idea what size props are on the boat now.

Can anyone with diesels suggest sizes? Thanks!
 
I am thinking you should be stock 3 blade at 25" pitch and 21" diameter. I have a chart some where I'll dig up and confirm.

Maybe Frank W. or Tobnpr will chime in on this...they are more familiar with the diesel side than I am.

John F.
 
You say your throttles are only "3/4 of the way to the stops" at 2800; what do you mean? With the throttles to the wall, was 2800 "it"?

22 kts @ 2800 rpm isn't right. I get 20-23 knots depending on load and conditions @ 2400, turning 20 x 25 props (3-blade).

First, you need to verify your dash tachs. Confirm your numbers with a photo tach, or better yet, invest in a set of Aetna digital tachs... best $500 you'll ever spend on your boat. I tore out the engine sync after installing them...

Something ain't right. Your speed at 2800 rpms is too slow- indicating your prop size is too small. But if your props were too small, you should be turning well over 2800 rpm at wide open throttle- more like 3000...

I had an issue with my port engine where it wasn't turning up- and it was a cable adjustment. Check to be sure that the throttle lever is pinned all the way to the stop on the fuel rack when your throttle is at WOT position. I found that mine wasn't- that I still had travel left, even though the throttle handle was all the way forward.

I assume you had a hull survey, but no engine surveys?
 
Here is a Prop Chart I found cleaning out a Boat Warehouse a few years ago. The title that is cut off says

"1989 Sea Ray Prop & Speed Chart"

SCAN0061.jpg




I re-typed this into XL. If anyone would like a copy, send me a PM and I will email the XL file to you.

Anyway,accordingly a 390EC w/3208s runs a 20" x 25"(pitch) at a max RPM of 2900 with a top speed of 32~36 MPH.

Hope this helps.

John F.
 
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I'll start with the tachs. I did have an engine survey done, everything appears fine. The physical throttles are only 3/4 of the way to WOT when the tachs are reading 2800 rpm.... Went out tonight with a full tank of fuel and 4 people and we were barely hitting 22 mph..... :( And struggling to stay on plane.
 
Forgot to mention...
Did you have tabs full down? Esp with the extra iron of the diesels- you need to run full tabs all the time to keep the bow down.
 
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