1989 39' SEA RAY EXPRESS CRUISER

J

JOHN RAY

New Member
Jun 9, 2006
1
Hello Folks:
I just found this site and registered. I hope to find an answer to a problem.
I have owned the above boat for approx. 3 years and previously only cruised around on short trips. Now I am wanting to get well offshore with it. It has twin mercruiser 454's which give me about 3 Gal./mile. What can I do to improve on that. I am considering Crusader 8.1 L engines, or is diesel the only answer.
Thanks, John
john@raysnursery.net
 
John,

The standard rule of thumb for offshore fishing is 2/3 of a tank going out, fishing and getting back, leaving the remaining 1/3 for reserve due to weather, emergency, etc... So how far you can go offshore is determined by gph burned & your tank size(s).

A fuel management system will help you to optimize your consumption-if you don't already have one.

The 8.1's are supposed to be great motors and may provide some improvement because they are fuel injected IE 5-10% maybe, but probably sized good quality diesels will likely get you 25%-50% better fuel consumption. So as you can see the diesels are going to get you the best results, if you can justify the costs of the diesels for your boat.

Please let us know what you find out and what you decide to do?

Kevin Smith, Richmond VA
1991 250/270 Weekender, 454 CI, 330 HP, Bravo II
 
39 EC

You may want to consider bigger wheels or go to 4 blade instead of the standered 3 blade props. My 39 came with 21/19. standered were I think 17s.
the bigger whells also gives me better response to helm which is great when docking. At 2900 RPM I'm burning approx 17GPH doing 13.5 to 15.5 K (Tide/wind).

Paul
 
John,

3 gallons per mile sounds Waaaaaaaaaaay high to me. How many gallons per hour are you burning? Should be around 30-34 at 3200rpm. Check out you WOT rpm and let us know what it is..... your props may be undersized or you need a serious tuneup.

BTW, 3Gallons per mile is .33 mpg. These boats typically do twice that with gas.
 
I agree...something is not right. the 454's should yield somewhere around 32- 36 gph........our 3 90EC with gas engines cruising at about 2800 rpms got right at 1.0 mile per gal.

Check bottom condition, check prop pitch against OEM whells supplied with the boat,check engine condition (compression, plugs, oil consumption, timing, spark intensity) look at the plug wires with the engine running on a dark night. The ignition wires are very bad to break down and arc.
 
fwebster said:
I the 454's should yield somewhere around 32- 36 gph........our 3 90EC with gas engines cruising at about 2800 rpms got right at 1.0 mile per gal.
Click to expand...

Frank:
You sure about the....1.0 MPG.....that would mean you were traveling between 32-36 MPH while burning 32-36 GPH...or are you referring to each engine....
 
Actually, I'm not sure. We sold the 390EC 10 years ago and a lot of water has gone under the keel since then.

However, notice the rpm's I mentioned. Our boat was efficient for twin 7.4 power, but anytime you got near the secondary opening point, the flowmeter began to hum. We ran the boat a good bit slower at more like 2800 rpm's, and paid for the efficiency gain with a cruise speed sacrifice. As best I remember, getting the rpm's down to about 2800, got the fuel burn under 20 gph and the speed was near 19 kt.

If you cruise at rated cruise rpm's of 3200, fuel burn will be 32-36 gph with speeds in the low 20's mph, and your calculations would be correct.

Sorry if I misled you..........
 
Guys I moved this from the Cruiser section to the Yacht section to help out with the search feature in the future.

Wesley
 
I just purchased a 1985 390 in September.
After a LOT of research- including discussions with my surveyor- I bought a 390 with CATS. The consensus seemed to be not to buy this boat with gassers- period- as it would be way underpowered. Because thousands of these boats were sold with big blocks I'm sure there are those that would disagree, but anyone who's claiming a cruise in the 20's with 454'w is full of :smt018

With the CATS, I cruise 21-22 kts burning 20-22 gph, right at 1 nmpg. I can't imagine trying to push that hull with gas motors. I don't know what percentage of these were manufactured with the diesels, but when I began shopping Yacht World had dozens of the gassers listed but only a handful of diesels. Some owners seemed to be willing to practically give the gas boats away- 40 grand or less. I'm also spinning 26" wheels, which makes her very responsive in tight quarters.

I'd try to get projected performance numbers from the engine manufacturer based upon your current numbers. If you need to repower because your motors are tired it's one thing, but if you're doing it for speed better make sure you're going to get what you expect before you write that check. Verify that your trannys and shaft size will accomodate the larger motors. If the performance numbers don't work with the gas motors, your options are to sell as-is (and buy a diesel boat) or do a diesel conversion. On that boat you're probably looking at $80-$100K...
 
My 1990 350 burns around 34-35 gph cruising at about 21-22mph. That is around 3300-3400 rpm. I average about .64 mpg. (not nautical) These figures are based on Floscan and GPS, and verified at each fill up. This floscan is amazingly accurate.

I can't imagine a much bigger, older boat like a 390 would get very close to my numbers. His .33 mpg would seem right to me. I am very calm freshwater so not sure if saltwater would help much?

Before I would repower that boat I would have to think long and hard about upgrading boats. Just my 2 cents.
 
My 92 370EC burns 15-16 Gal per engine at 3000 - 3100 RPMs w/ 454's. This cruising speed is where I normally run the boat in all conditions and for 3 years know that has never changed. And I'm usually cruising at 20-23 MPH.

The gas engines are fine on this boat and agree, before I would repower to deisel I would upgrade.
 
Repowering a 39 with diesels and new genny will cost more than the boat is worth. Even 8.1s at 35-40k is a question. It really depends on the structural condition of the boat. If that is good, you would really have to love this boat to spend that kind of money.
 
Late answer in UK gas prices are 12$ per gallon now
I fitted two hammer head 300hp supercharged motors alloy headers stainless risers weight less than 454 s used 12 ltrs per hour each engine at 2.5 rpm so in your measurements less than 5 gall per hour for 22 knots both motors they make over 509 lbs torque @ 1.5 rpm these are a no brainer in the UK as we can use marine red diesel at £1.03 per ltr
 
goblue said:
Repowering a 39 with diesels and new genny will cost more than the boat is worth. Even 8.1s at 35-40k is a question. It really depends on the structural condition of the boat. If that is good, you would really have to love this boat to spend that kind of money.
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