What’s not to like about Diesels!

[1stSeaRay]

Well, one thing not to like about diesels is that my boat doesn't have one!

 

[Bel_Mar_Pointe]

Diesels suck!......less fuel. :grin:

I'm with the group here. I want two things on my next boat.....inboards and diesels.

 

[stephane]

you could plane at lower speed cause a gasser need hight RPM to have enough torque and HP to keep the boat on plane. when you lower the RPM a gasser dont produce enought HP and you loose plane. Diesel are different they have more HP at low RPM so even if you lower your speed the engine still have tone of torque and will not loose the plane. The minimum I was able to cruise with my 454 was 23 MPH now I could go as low as 18 and will never loose the plane

 

[stephane]

On balance, diesel doesn't really make sense where we boat for the following reasons:

1. In a good season, we may put 50 hours a year on the boat. Even boating in May and October can be iffy, weatherwise.

im in tousans island and will do at least 80 hour this year for shure it is not a lot but I will save at least 5000$ in gas

2. The regular mechanics in this area aren't terribly knowledgeable working on them. To get a "good" diesel mechanic here, you have to send for someone 100 miles away and often are waiting a long time for service.

yes but they are a way more reliable and dont broke plus they are realy simple and easy to fix

4. Only about 50% of the marinas around here stock diesel fuel. Those that do don't seem to sell a ton of it, which makes me wonder how fresh the fuel is.

diesel stay fresh longer than gas so it is less an issue

If you own a model that can be pushed around adequately with gas motors, the "economics of diesel" argument doesn't really hold up as well here as a location with a 12-month boating season where you can rack up many more hours. If I were operating a boat much larger/heavier than this, I would prefer the torque of diesel motors, of course...

If you Follow me for a week in holiday you will understand the real difference, anyone do boating with me at first dont get it but after a couple of ride together they all want diesel

 

[terminaldegree]

I appreciate the diversity of opinions, stephane... I'll also keep an eye out for your boat when I'm up there in a week (for privacy's sake, you're welcome to PM the info if you prefer).

I still don't think the math adds up. In the case of our boat, let's assume the diesel takes 17 gph total for cruising speed while the gas engine needs 30 gph to do roughly the same speed.

diesel boat @ 50 hours: 850 gallons
gas boat @ 50 hours: 1500 gallons

(this is, of course, already overestimating fuel usage because 100% of running time is not at cruising rpm)

Last time I was there, gas was $3.20 and diesel was roughly 25 cents more, if I recall correctly. That figure could be off slightly as I don't watch the diesel prices as closely.

Diesel boat @ 50 hrs: $2932.50
Gas boat @ 50 hrs: $4800

Given how little we run, it doesn't make a lot of sense unless the boat really needed diesel power to run well. If we ran more, or had a heavier boat, or had ready access to a qualified diesel mechanic, then diesel would be a good way to go.

 

[magster65]

You're right about the Hull being the limiting factor....you won't get a 410DA to plane at 10 knots....not gonna happen.

But, start by understanding that motors don't move boats, Props move boats.

Motors, of course, are what turns the trans that turns the props that moves the boat.

In all planing hull boats, designing the props/motors/trans to work together is a compromise. You have to be able to spin the prop fast enough to get the boat on plane and then once on plane, be able keep the boat there and move it at a reasonable speed.

That said, with gas motors, there is less torque to start with, so in order to spin the props fast enough to get on plane, you can either cut out pitch (which will kill your cruise speed) or increase gear ratios in the trans.....like putting your ten speed bike in first gear....more teeth, higher gear ratio....again...designers have to find the happy compromise.

With Torquey diesel motors, you spin a higher ptiched prop through lower gear ratios to get the boat on plane.....like starting off ten speed bike in 5th gear or so....so the boat actually gets on plane at lower RPMs and will cruise faster at planning RPMs.

Again, the Hull will determine the lowest speed it can hold plane, but the motor has to be able to spin the prop to keep it there.

I hope I explained that right.....:smt101

You did... well said.
I'm extremely happy with my 290 but my next boat will be bigger and have diesel power.
I'm lovin' the fast trawler idea at the moment but it'll be a few years before I can make a move like that...

 

[320Bob]

Another reason to hate diesels - a carbon tax. Diesel fuel has 50-80% more carbon per gallon over gasoline. Use less but pollute more. If the libs fail on this initiative then maybe my next large yacht might have a pair!:smt001

 

[FireIsland1]

not too long ago you could buy a gas boat, keep 50 ro 60 k in the bank. then pay for all the gas for the season just off the interest. Well that changed. Now you are lucky to get 1%. That's not going to get you too far on the water.
So i agree with everyone else. you pay up front more and when you sell you get more back.
if your going to move a heavy weight 22k+ lb , I don't thing you have much of a choice.
but I do question this idea that diesels get all these hours and low cost of maintenence.
I often wonder why there are so many deisel boats for sale with new engines.
I am seeking a new boat now probably will be a diesel. More then 25% of the boats i looked at had either one of both engines replaced or have a maintenance record as long as my arm. turbos, heads, valves, injectors, intercoolers, oil pumps, heat exchangers, transmissions are all some of the heavy items that i have seen replaced. oil leaks seem to be a major problem. Most of these repairs need a highly trained mechanic not just a parts replacer.
The boats I am looking at will need diesel power to run properly, and that's where I heading. But boy is it nice being able to buy Merc parts any where you travel. So don't sell these gas engines short. Hell when the "s" hits the fan and you pop a gasser just pull out a credit card, drop in a new engine and go boating. The seasons never over if you own Mercs. It's just an unplaned expense.

 

[fwebster]

You will find that most, not all but most, serious issues with diesel engines are directly caused by the owner not understanding the importance of proper maintenance and loading. In pleasure boats, nearly every replaced head, blown head gasket, etc. is the result of overheating or overloading. With a gas engine, you can run one hot, let it cool off and try again, but diesels with their higher compression and closer tolerances are not nearly as forgiving.

If you think you can run them forever and not worry about maintenance, then stick with gas motors, a paddle or a sail.

 

[OldSkool]

You will find that most, not all but most, serious issues with diesel engines are directly caused by the owner not understanding the importance of proper maintenance and loading. In pleasure boats, nearly every replaced head, blown head gasket, etc. is the result of overheating or overloading. With a gas engine, you can run one hot, let it cool off and try again, but diesels with their higher compression and closer tolerances are not nearly as forgiving.

If you think you can run them forever and not worry about maintenance, then stick with gas motors, a paddle or a sail.

Frank, you are spot on. Diesels are great engines and will last for a long time when maintained properly. You won't see a gasser go 8000-10000 hours with minor repairs and service like a diesel will go.
Truth be told, I have larger engines with 15,000-18,000 hours still running on heavy equipment.
One thing that will kill a diesel is prolonged idling. Their like a mule. The need to pull to stay fit. Take them out, get them warmed up and throw the throttle open from time to time.

 

[SeaNile]

I can't imagine how a 340 Dancer with Yanmars or 6bta Cummins would not be the ultimate boat. I'm shopping for a 340 and the only thing that scares me is the gas engines. Coming from a diesel boat I said I would never return to a gas boat.

Once you have diesel you'll never go back. Simple, but necessary, maintenance and you are good to go.

 

[HUMPH]

Another reason to hate diesels - a carbon tax. Diesel fuel has 50-80% more carbon per gallon over gasoline. Use less but pollute more. If the libs fail on this initiative then maybe my next large yacht might have a pair!:smt001

But with the new tier 4 diesel engines.....very clean!

 

[Lord Farringdon]

There is something missing in the discussion here so far. Larger 34 foot plus boats need to be powered by torque emitting diesels otherwise they just wont work. In contrast, 26 foot boats really don't have any room for a diesel and even if they did, the economics of selling a small boat with an expensive engine just wouldn't work either. It is only really in the 28-32 foot range that the choice of diesel vs gas exists as two viable options. Given that size range, the economics of a diesel are directly related to how often you use it. After all, would you really pay a 10, 20 or even 30 percent premium on the capital purchase price of the boat if you were only going to use it 20 hours a year? But, if your considering long term ownership with reasonable running hours per year, then a diesel is a good option since you won't have to replace the motor for some 5000 hours (assuming you have maintained it properly) and operating costs are far less when you take into account the lower fuel consumption of diesels.

Of course in New Zealand we have the added bonus of diesel costing less than gas and of not having to pay road tax if it is used for marine purposes. I note this does not always seem to be the case in the US. The price of gas at the pumps in NZ is $NZ1.76/$US1.24 per litre whereas for diesel it is $NZ1.19/$US0.84 per litre. Given the significant price advantage of diesel, the lower fuel consumption of a diesel engine, that fact that I purchased the boat at a favourable price, the fact that I intend to use the boat moderately all year round and that I intend to keep the boat for 7-10 years (unless I win lotto), a diesel is really the only choice. The boat is arguably safer both in terms of fuel vapour issues and in general reliability at sea (once again assuming good maintenance is carried out).

Finally, I don't subscribe to the idea that diesels are more difficult to maintain. Having said that I am new to diesels but apart from injector and fuel pump disassmbly, (I'll remove but will not disassemble) I am more than happy to carry out other work on the engine including removing/disassembling turbos' and superchargers. But let's be honest, if the engine is properly maintained (turbochargers go bad because oil is not changed or the engine is shutdown with allowing the engine to idle cool first), then this kind of work is not required very often. In contrast, regularly checking the Racor for water, changing oil, impellors, drive belts, primary/secondary fuel filters, oil filters, air filters etc is childs play and if you can't do it yourself then any old truck mechanic will do. There are no sparking systems to worry about.

So there you go. If you own (or aspire to own) a boat in the 28 to 32 foot size, you are blessed with quite viable options of gas or diesel. For some, the economics of a diesel engine will not stack up, while for others it will make perfect sense. Personally, I can't imagine owning a gas Sea Ray. Fact is, I couldn't afford to!.:grin:


Terry