gas vs diesel

R

remo1950

New Member
Aug 19, 2010
10
Chatanooga, TN
Boat Info
I al looking to buy a 1998 to 2001 Sea Ray 40 either gas or diesel
Engines
7.4 efi or Diesel
I am currently looking at two 1998 Sundancer 40s. One is gas with 950 hrs and the heads have been reworked lately. The other is Diesel with 1300 hours. On the average because conditions vary, but on the average how much life is left in the gas and how much life is left on the diesel. Both look to be in generally the same condition looks wise.
 
Welcome to the forum. Try the search function for gas v. diesel, it's been discussed many, many times...nonetheless, I'm sure this thread will go to ten pages....

But to give you a short answer on your specific question, "most" will consider gas engines to be mol on borrowed time- particularly on a 40 footer where they shouldn't be in the first place and live a very hard life- after around 1000 hours.

Twelve year old mechanical diesels, PROVIDED they've been well maintained, not overloaded, etc. will easily go another 1300 hours to 2000 hours before they should need any type of overhauls.

Of course, anything can happen- it's a boat. And there are many other things to consider besides engine life-that's why I suggested a search.

Good luck.
 
What usually "gets" gas engines is water intrusion from failed exhaust castings. If yours has had the heads reworked, I would not even consider the boat unless someone could show me receipts for new manifolds and risers. This is a $4-6000 bullet you will bite if the work has not been done. Not many gas boats see 1000 hours on original engines.

The 40 is either an EC or a DA so it will have cummins 6BTA's or Caterpillar 3116/3126 engines. Neither one is hardly broken in at 1000 hours if they have been maintained. My Cat engines are at 1300 hours and still don't even get the oil dirty before changes.

For me the biggest differences are going to be in handling, (the diesel boat is a dream to handle; gas boat takes some effort and throttle) maintenance (diesels are easier and my experience shows cheaper to maintain, but I do my own maintenance), economy (diesel burns 20-22 gph; gas will burn 32-36 gph), resale value (you will pay a little more for the diesel and you get virtually all of it back at resale, but selling a 15 year old gas boat north of 1000 hours means you take a huge depreciation hit on the value at resale.

If the over all condition of the 2 boats is comparable, this one isn't even a close call for me........buy the diesel boat.
 
Is more vibration normal with the diesel over the seemingly smoothness of the gas engines.
 
Frank- you were typing while I was responding to a pm from remo re; the vibration issue. Hope you don't mind- I suggested he pm you as the resident 3116 expert...

Ken,

Kids have grown (as they do!) over the past four years and no longer enjoy cruising. I'm a fisherman/diver, and no longer need all the amenities (and the headaches of maint.) of a 40 foot condo. I'm actually going to be looking for a center console this winter (that I can hit with a hose at the end of the day to wash the blood off the deck), but took the 30 DA in trade to make the deal work. I figure it's easier to sell a 30 foot gasser in this tight market than a 40 foot diesel- time will tell! In the meantime, I'm going to enjoy the 30 DA (at least I can still fish off her!) as I get ready to place her on the market. Northern Lake Superior boat until last year, in great shape and below market- shameless plug, Jim...

Anyway, Doc should have the 390 to Mobile, AL by now. They were in Destin on Fri. afternoon after crossing the Gulf of Mexico Thursday night.
 
remo1950 said:
Is more vibration normal with the diesel over the seemingly smoothness of the gas engines.
Click to expand...
This is in response to te question of smoothness between the diesel DA and the gasser Da. I own both a 1998 400 and a 2002 510. when I take the 400 out for excersise the first thing that hits me is the relative smooth and quiet on the 400. Now I don't know if this is a fair comparison because the 510 is much bigger and has twice the power. Maybe a better comparison would be between a 400 gasser and a diesel 400. The other thing as Frank has said the diesel is a dream to handle compared to the gasser. Docking on windy days with the gasser will truly test your skipper skills. The diesel on the other hand makes up for my lack of skill.
 
The engines in the 40 are inline 6 cylinder regular, not light weight, diesels. If they are Caterpillars, I think the engines will be smoother than 7.4 gas engines. Cummins seem to have a little more vibration than Cats, but it isn't hardly noticable.

If you find a pair of cats that vibrate, they are idled too slow or something is out of adjustment.
 
fwebster said:
The engines in the 40 are inline 6 cylinder regular, not light weight, diesels. If they are Caterpillars, I think the engines will be smoother than 7.4 gas engines. Cummins seem to have a little more vibration than Cats, but it isn't hardly noticable.

If you find a pair of cats that vibrate, they are idled too slow or something is out of adjustment.[/QUOTE Good point Frank, maybe I should say the 7.4s make less noise.
Click to expand...
 
I guess smoothness is relative to the guy driving the boat..........and the size of the boat or platform supporting the engines.

Obviously, I have more experience with my own boat that others, but in my case, I find that the sound deadening and distance from the engines make a lot of difference. While it is one of my favorite boats, the 370EC with the engines right under the bridge deck seems loud and I feel everything on them. The same engines is a 400DA or 450DA feel a lot smoother and quieter.

The truth of the matter is that the OP is going to find that the Westerbeke diesel generator vibrates more and makes more noise than his engines will..........
 
Indeed something that is discussed around our docks pretty much every week....

There are the basics; cost, fuel, etc etc....but we always seem to come back to this:

If you have a gasser going 25 knots, the engines are revving high and it feels like it. A diesel will churn along all day at 1900 RPMs at the same speed and it just doesn't feel like they are working as hard.
 
Uh...diesel if you want any performance...
 
to me, it depends on your driving style, I can drive for days at 6 knots, (more fun per gallon) what's the hurry, from what i've heard, diesel's don't like to go slow for days on end (although i could be wrong) and then try and buy a new diesel, 60 grand or so as opposed to 6 grand or so for a big block. if you want to cruise at a decent speed and have resale, diesels.. i have over 1500 hrs on mine and they run like champs!, hold em wide open and burn 55gallon per hour (which kind of s..ks) or go slow and get 1 mile per gallon..
 
Last edited:
dantheman said:
or go slow and get 1 mile per gallon..
Click to expand...

I'm looking into diesels right now, actually have a contract on one but from another manufacturer, and the diesels qsb5.9's get 1.2MPG at cruise, yes at 28MPH. Hell if you wanted to go slow in diesels they get something like 3 or 4mpg. I could be wrong but from the information I have one the boat we are trying to purchase, those are the numbers.
 
I drove my 400DA with Cat 3116 engines for 32 days at 500 - 600 rpm down through the French canals last summer, (speed restrictions all the way) and when we finally reached open water, the slightest puff of black smoke and all was fine.

In total we did about 230 hours at that speed, and the engines always started instantly hot or cold, never ever stalled and were not affected by the experience at all. Probably the biggest downside was the additional hours on the clock, but saved about US$20,000 from the cost of shipping UK to the Med, and had a stunning summer as a bonus.

To me the choice is a no-brainer, Diesel every time

Graham
 
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