04-06 390/40 sundancer. DIESEL Question

Before I purchased my 390 last year I made an excel sheet with all the 04/05 390’s and 06-08 40’s in the whole country and listed every single option and their engines. For my $200k budget I quickly removed the 40’s... I started focusing on 390’s. It came down to two of them.

One was loaded with all the options, gas 8.1HO with 380 hours. It also had a lot of options added aftermarket.

The second was a diesel that was $15k more and had absolutely nothing on it, totally stripped.

For my budget and after weighing both of them for days I went with the gasser. Ideally, diesels would be more efficient, doesn’t take a rocket scientist to know that. However for our boating style we couldn’t justify it. Our longest trip is 3 hours one way. Most of the time we go 20 minutes to a bay, throw hook for the day and drink water.

The gassers have no problems with a jestski and a crew on board. Like I said before, it’s a gas hog but this isn’t the hobby to be involved in if you’re worried about that.

My point is, buy the most boat you can with the budget you have. We chose all the options over the one big option and I don’t regret it at all
 
My point is, buy the most boat you can with the budget you have. We chose all the options over the one big option and I don’t regret it at all

Hmm. I heard that your boat is a trawler that burns 58 gallons an hour. It was on the internet, so it must be true...
 
For the record, I love diesel. I just don’t have enough wealth to own own. Two hours ago at the boat show, I ran into friends that bought a 420 2 years ago. They told me about the $25,000 in repairs on their port 6CTA...

At least that’s not as bad as my dockmate. The rebuild on his Volvo last summer was a lot more than that.
 
I can't imagine owning a boat that size with gas engines.
Many moons ago I repowered a 31 Bertram from 454's to Cummins 6BTA diesels. Saying it was like a new boat would be an understatement. There was not one single downside from going to diesels.
 
I can't imagine owning a boat that size with gas engines.
Many moons ago I repowered a 31 Bertram from 454's to Cummins 6BTA diesels. Saying it was like a new boat would be an understatement. There was not one single downside from going to diesels.

I think Rollrcoastrs point is for someone without the financial means to cover a major diesel failure makes the decision more difficult.

We are going to be looking at 400/410's in the coming few years. We're great lakes boaters that do a few trips a year but mostly 2 mile runs to a cove. I do not have the financial situation to allow for a repower or rebuild of a diesel engine. I would agree they're more durable than gassers, but my anxiety level each and every time I turn the key on a diesel powered boat would be pretty high. If we were to blow a motor our season(s) would be over. Not saying gas maintenance is cheap, but a rebuilt of a BBC is more within our reach and I could do most of the work myself.

I'd love diesels, but boating is a luxury and we will take a long time to consider both power options
 
Let’s take a closer look at this. Spit the difference and say 23.5 sMPG, returning .5 sMPG. That means he’s burning FORTY SEVEN gallons per hour?!? Has no-one questioned that during your several hundred mile journeys???

On second thought, don’t encourage him to join CSR. He should get out of boating.
I'm not sure why you're getting upset but no we have not questioned it but we do all make fun of him. It's a 40 foot boat with gas engines and last I checked it was close to the rated mpg when fully loaded. If you're getting .75 mpg fully loaded (based on the feedback on here) good for you. Sounds like you like the gassers and there are lots of benefits to gas. Fuel economy just isn't one of them.
 
We will be in the same market in a few years.
 
I'm not sure why you're getting upset but no we have not questioned it but we do all make fun of him. It's a 40 foot boat with gas engines and last I checked it was close to the rated mpg when fully loaded. If you're getting .75 mpg fully loaded (based on the feedback on here) good for you. Sounds like you like the gassers and there are lots of benefits to gas. Fuel economy just isn't one of them.

I'm annoyed by ridiculous "data" that's being passed-off as reality.

.5 is a nightmare

.4 is nearly impossible

There is no such thing as "rated mpg", so what did you "check"!?

I never said fuel economy is a benefit to a big gasser

I didn't say I get .75 fully loaded. I said the opposite of that. My fuel meters provide me with enough accurate data that I can run lighter than I ever could based on factory fuel gauges. With light tanks, kind seas and a clean bottom, a 400 gasser can run reasonably fast and return close to .75 sMPG.

Now that I mentioned questioning the fuel burn your friend is experiencing, will you suggest he question it? It may be too late. He may gave stressed those engines (and perhaps the trans too if he's running around at 4,500 rpm) and already significantly shortened their life, all the while going slow and wasting huge amounts of fuel. That's sad.

Even more sad would be if he continues to question nothing and moves to diesel, where he'd likely be the guy who over-loads his engines for a few seasons before he hears the BANG my friends and neighbors did last summer. Maybe he's fortunate enough to have 30 grand sitting in a just-in-case-of-a-BANG account. Maybe he'll be fortunate enough to get insurance to cover it, and maybe it won't be underwritten by the same company I have so I won't have to help cover his loss by way of increased premiums...
 
I can see the argument by some for gassers in the 390. I never really looked at them as a prospective buyer, but they are closer in size to the earlier 380’s and I did look at a lot of 380’s and all but 3 in the country that were for sale over the year I was looking for a boat were gassers. I suspect that gas 390’s are probably more common than diesel versions too.
Having never owned one and knowing little to nothing about them it was a leap of faith for me to move to a diesel boat, but after a year of ownership I have absolutely no regrets at this time. I do have some concern about cost to repair a major failure, but on the other hand I’m pretty good with maintenance and don’t really beat them up so odds are tilted in my favor.
I shifted gears to a search for a 410 because diesel versions are far more common than gassers.
Several people I know with bigger boats kept telling me that I would regret getting a boat in that size class that wasn’t diesel. Knowing that the long term plan is to do longer trips where fuel burn and reliability were a concern a diesel made more sense for me.
A diesel 380 was out of the question. They were so rare that two of the three for sale were actually priced higher than 410’s and the third was priced about the same as a 410. I looked at that third 380 and describing it as a dog would be generous.
If a gas 390 is what the budget allows and it suits the buyers needs then he shouldn’t hesitate buying one. There are a lot of gas boats out there in that size class and I’m sure their owners are enjoying them.
Anything bigger though and I would be very hesitant to go with gassers unless the buyer planned on very low annual hours and wasn’t overly concerned with resale.
 
For the record, I love diesel. I just don’t have enough wealth to own own. Two hours ago at the boat show, I ran into friends that bought a 420 2 years ago. They told me about the $25,000 in repairs on their port 6CTA...

At least that’s not as bad as my dockmate. The rebuild on his Volvo last summer was a lot more than that.

A friend of mine with a beautiful 2005 420 heard that same bang last summer. It turned out to be a result of a faulty early head design on the Cummins motors. The only silver lining was that the Cummins guy he uses was aware of it and let him know that he could push Cummins for some restitution. I think they were negotiating to cover the cost of the parts and he paid for the labor.
It was a design issue, not a diesel issue.
Not sure what years the Cummins motors had the affected head design but the mechanic called it as soon as my friend contacted him to come and diagnose the problem.
That boat sure runs sweet though.
 
I wish I had some sales figures, but I'd guess that 60% and maybe more of 400DA's in the Great Lakes are gas. I've never personally seen a diesel 380DA in the Great Lakes.

410's seem to have been a higher proportion of diesels up here. Maybe 50/50?

By the time 420's were introduced, it seemed like at least 80% were diesel - maybe even higher. I know of a few gasser 420's, but I've never been on one.

I'm not sure why that was the case. It's not as if diesel is hard to come by, or that GL boaters don't like to travel long distances and anchor out...
 
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A friend of mine with a beautiful 2005 420 heard that same bang last summer. It turned out to be a result of a faulty early head design on the Cummins motors. The only silver lining was that the Cummins guy he uses was aware of it and let him know that he could push Cummins for some restitution. I think they were negotiating to cover the cost of the parts and he paid for the labor.
It was a design issue, not a diesel issue.
Not sure what years the Cummins motors had the affected head design but the mechanic called it as soon as my friend contacted him to come and diagnose the problem.
That boat sure runs sweet though.

The dreaded valve-seat issue? I thought that was widely believed be a design issue compounded by over-loading? A bummer for sure, but I too have heard that Cummins will help.
 
The dreaded valve-seat issue? I thought that was widely believed be a design issue compounded by over-loading? A bummer for sure, but I too have heard that Cummins will help.

I don’t know all the details but he was satisfied with what Cummins did for him and those motors run great and really move that boat along nicely.
It happened in the middle of the season and I think he was back up and running in about a week after the dreaded bang.
Mechanic said that anyone looking at a boat with those motors should check the casting numbers on the heads and factor in the cost of replacement to the price if it wasn’t already done. He estimated 7500 per motor for parts and labor if done before failure.
 
Hi thanks for all the Input ! This boat was brought to my attention ,and the price is actually way lower then the asking prices of the gas motors on today's market , it has 500 hrs on the qsb380,s . I spoke to the mechanic that services this boat and he tells/has records , that the boat was serviced 3 times a year, and really hardly moved , the PO ,had the boat washed weekly and waxed every other week.The PO. Is a corporate BUISNESS owner ,in an exclusive yacht club, so he serviced the boat with open check book, and owned the boat 8 yrs , he's moving up to a 580 ,
I am scared , of the diesels , a little , as I've never owned them. But the gas boats in my area are 15 to 20k more then this, boat has all except bow/stearin thrusters k, and hydro platform , thrusters I like platform don't need , I'm getting a survey and having the cumming expert survey the motors ,
Blue white ,hardtop ,cockpit air, track vision , I'll see you on the water roller coaster, I'm at sunrise ,
 
Ask the Cummins expert if he is familiar with the valve seat issue, if the motors in the boat you’re having surveyed are effected by it (hopefully not), and if so, if the casting numbers on the heads indicate if they’ve been replaced (hopefully they have).
If they are effected but have not been replaced, ask him for an estimate of replacement costs and factor that in to your decision.
If you proactively replace effected heads (smart move)before there is a problem you will probably have many trouble free years. I know the 420’s of that era cruise beautifully with those motors so the 390/400 should be even better.
If you don’t do it you risk a catastrophic failure when chunks of the valve seat score a cylinders walls, chew up a piston or do further damage when particles circulate through the oil system.
If you really want the bow thruster you can get one installed soup to nuts for about 10-11k.
My boat didn’t have one, I really wanted one, the purchase price left room for one, so I had a Vetus 9524 installed as soon as I closed. Considering the set up at my dock property, it was well worth it to me. Getting in to the bulkhead would otherwise be a challenge in certain conditions for better boat handlers than me.
 
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i dont know how a 400 with gassers is doing 23mph and 0.75 mpg..

my 340 with light loads, 496 mags, is doing .8-.9 and 24-25mph.
 
I will ask about the valves and heads ,it's less expensive to ask,THE DUMB QUESTION IS THE ONE YOU NEVER ASKED ! Lol,
I'm thinking to use the same thruster, I WAS GOING TO USE EAST COAST THRUSTERS !! They want 11k for the 9524, They will be in my area 2nd week April,
Did your installer install a battery charger for the thruster battery ,
thanks again
 
I'm annoyed by ridiculous "data" that's being passed-off as reality.

.5 is a nightmare

.4 is nearly impossible

There is no such thing as "rated mpg", so what did you "check"!?

I never said fuel economy is a benefit to a big gasser

I didn't say I get .75 fully loaded. I said the opposite of that. My fuel meters provide me with enough accurate data that I can run lighter than I ever could based on factory fuel gauges. With light tanks, kind seas and a clean bottom, a 400 gasser can run reasonably fast and return close to .75 sMPG.

Now that I mentioned questioning the fuel burn your friend is experiencing, will you suggest he question it? It may be too late. He may gave stressed those engines (and perhaps the trans too if he's running around at 4,500 rpm) and already significantly shortened their life, all the while going slow and wasting huge amounts of fuel. That's sad.

Even more sad would be if he continues to question nothing and moves to diesel, where he'd likely be the guy who over-loads his engines for a few seasons before he hears the BANG my friends and neighbors did last summer. Maybe he's fortunate enough to have 30 grand sitting in a just-in-case-of-a-BANG account. Maybe he'll be fortunate enough to get insurance to cover it, and maybe it won't be underwritten by the same company I have so I won't have to help cover his loss by way of increased premiums...

Ok but I'm not using "ridiculous data" for his numbers. We are literally dockmates so we fill up at the same time before we leave on big trips and fill back up at our destination or when we return. He gets in range of 0.5mpg around 3500 rpm and I get 1.0mpg. Both are fully loaded with fuel, water, dinghy's etc. We use our actual gallons used vs miles traveled so we know the math is correct.

I assume he would get better economy with little fuel or water and no gear but reality is that most people don't travel like that. I can load whatever I want and see no difference in speed or economy. I'm not against gas at all, and some day I would likely go back to it with a smaller boat, but for long distances fuel economy just doesn't compare.

If you're strictly talking about major repair costs on a failure, then no question gas engines are FAR less to repair.
 
I will ask about the valves and heads ,it's less expensive to ask,THE DUMB QUESTION IS THE ONE YOU NEVER ASKED ! Lol,
I'm thinking to use the same thruster, I WAS GOING TO USE EAST COAST THRUSTERS !! They want 11k for the 9524, They will be in my area 2nd week April,
Did your installer install a battery charger for the thruster battery ,
thanks again

We had a Side Power installed 10+ years. They put 2 AGM 27's in the floor next to the thruster and ran O1 cable to a battery combiner next to the house batteries and tied into them. I have never run out of thrust.
 

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