Gas vs Diesel

Argon6868 · Post by **Argon6868** » Mon Aug 17, 2009 10:31 am

Dear Forum Members

I know this question was raised many times but as the fuel prices are much higher in europe than where most of the Forum has their ships I am deeply think about change to Diesel enginees.
I am looking for any info from people which have done that I have a tri cabin with V drive 1973 with Merc 255 they run ok but in the french canals we have most of the time a speed limit and on the Rhine River you need a big sponsor to drive them to 4000 U/min

many thanks
Dani

jav · Post by **jav** » Mon Aug 17, 2009 11:43 am

Dani-

I have done the conversion. I found it very worth while but there are different opinions- usually from those who have chosen not to do it. I don't know of a single person that has made the conversion and regretted the decision.

If you have any specific questions- ask away.

prowlersfish · Post by **prowlersfish** » Mon Aug 17, 2009 12:02 pm

Diesels are the way to go IMO

TADTOOMUCH · Post by **TADTOOMUCH** » Mon Aug 17, 2009 1:49 pm

Diesel is better, safer, more power, more effecient. You will probably never recover the cost due to fuel cost or economy savings but, they are the better way to go if money is not an object.

k9th · Post by **k9th** » Mon Aug 17, 2009 2:16 pm

I have been contemplating doing the same thing with my Merc 255's. I have a question that I have wondered about. I am sure that not all diesels weigh the same but generally speaking, are the diesels a weight neutral exchange, and if not how much more or less displacement can I expect?

jav · Post by **jav** » Mon Aug 17, 2009 3:51 pm

as a general rule, diesels are a little heavier than gas engines for the same HP output. There are some newer extremely lightweight diesels that challenge the premise but they've not found wide spread acceptance in the marine field.

Generally- with newer pleasure duty marine diesels (170-375 hp)- 4 cylinder diesels with gears weigh around 1,000 pounds each- 6 cylinders with gears around 1200 pounds each- give or take 15% depending on mfg/technology/marinization.

ready123 · Post by **ready123** » Mon Aug 17, 2009 3:57 pm

I come from the school of sell a gas boat and buy a diesel boat rather than convert....
IMO the advantage of having a boat designed around diesel engines is a much better solution to shoe horning a diesel engine as a replacement for gas.
There are many old and new boats available designed around diesel plants, one of them should meet your needs.
I have seen too many negative compromises made when converting gas to diesel .

jav · Post by **jav** » Mon Aug 17, 2009 6:40 pm

ready123 wrote:I come from the school of sell a gas boat and buy a diesel boat rather than convert....
IMO the advantage of having a boat designed around diesel engines is a much better solution to shoe horning a diesel engine as a replacement for gas.
There are many old and new boats available designed around diesel plants, one of them should meet your needs.
I have seen too many negative compromises made when converting gas to diesel .

I generally agree with the "buy" versus convert premise. It makes much more sense financially. BUT- many Trojans were designed with diesels in mind (the F-32 & 36 were) so there really is no shoe horning in most cases.

Also- if you really like your boat, it can make sense to upgrade what you know and like versus buying an unknown.

MattSC · Post by **MattSC** » Mon Aug 17, 2009 8:01 pm

I had actually looked into a diesel for my F-26, a 240HP Yanmar. It could have been done, but the shaft log would have had to be redone to accommodate the 17" Prop which was recommended. It actually would have given me more room as it is a bit smaller size wise than my 5.7 Crusader, but I could completely re-power again "bobtail" and it would still cost a little less than the diesel conversion........though I was seriously tempted.

k9th · Post by **k9th** » Mon Aug 17, 2009 8:58 pm

My 36 Tri-cabin has plenty of room for diesels and I have a sound hull and love the boat so I am not about to try to sell the boat and try to find another boat as good as this one with diesels. That sounds like too much of a gamble.

I am not sure what kind of diesels I am going to look for, but generally speaking money is not the deciding factor. I want some engines that will last me a long time since I plan to keep this boat at least 10 years.

Are diesels similar to gas engines in that most of them are GM engines that are privately labeled?

MattSC · Post by **MattSC** » Mon Aug 17, 2009 9:31 pm

There are several different manufacturers of Diesel engines: Caterpillar, Cummins, Volvo Penta, and Yanmar to name a few. They are all different designs and in not affiliated with GM, though GM did produce several diesel marine engines.

Something you also might consider in your decision, is how many hours you put on the boat each year. If you only put 100hrs a year on your boat, I'd look at some of the fuel injected gas engines as an option, possibly a 6.2 or an 8.1. Mercruiser or Crusader. You'd be surprised at the performance they give, and they are alot more cost effective. I replaced my raw water cooled LM318 when it was 27yrs old and had over 1800hrs on it. With care, a gas engine will last, especially if you are in fresh water. Though if price isn't a factor diesels are great too.

prowlersfish · Post by **prowlersfish** » Mon Aug 17, 2009 10:01 pm

ready123 wrote:I come from the school of sell a gas boat and buy a diesel boat rather than convert....
IMO the advantage of having a boat designed around diesel engines is a much better solution to shoe horning a diesel engine as a replacement for gas.
There are many old and new boats available designed around diesel plants, one of them should meet your needs.
I have seen too many negative compromises made when converting gas to diesel .

? negative compromises? Like what ? I would think the pros out weght the cons by far

LandVF36 · Post by **LandVF36** » Mon Aug 17, 2009 11:00 pm

So, those of you that have converted, what did you spend again? I sent a note to Mercruiser last week after seeing and add for their new marine diesels somewhere. Thle add claimed to have new options for dimensionally equiv models to replace my GM 454s. The new engine was a common rail 6 cyl model, gears and guages ..... $79K.

I love my boat, a but I can buy a lot of gas and parts for the old blocks before I'm going to burn through that kind of fuel.

Is this price what others have spent on a new swap to Diesel?

prowlersfish · Post by **prowlersfish** » Tue Aug 18, 2009 6:52 am

You can do it a lot cheaper get a set of running take outs or cummins remans and do the work your self . What size mercs were you qouted on ?

RWS · Post by **RWS** » Tue Aug 18, 2009 7:01 am

You better LOVE your boat and plan on keeping her for some time if you choose to do the conversion.

The genset is an additional consideration.

In an older boat like ours, it really does not make sense if your gassers are working fine.

If you are faced with low compression, and worn out engines it's at least worth a look.

My 454's had over 2600 (that's right) hours on them and the bolt on components were tired. Things like the leaking heat exchangers needed to be replaced.

Rebuilding the 454's would have been the least expensive thing until I figured in the replacement cost of the bolt on components combined with the zero increase in value that would be derived from this repair. one, three, five or ten years after the 454 rebuild, the boat is worth no more than any other similar model.

New 8.1 Crusaders made more sense, increasing the effeciency and range, but they would have required larger raw water intakes and new Aquamet shafts to be well within the safety zone.

The boat would have been a bit more valuable 1, 2 or 5 years later.

The DIFFERENCE in cost between the 8.1's and th Yanmars was what made the choice a bit easier. She'll be much more valuable 1, 2 or 10 years from now.

More importantly, the increased range higher, more efficient cruising
speed, safety factors, reliability and decreased operating costs are a big plus.

Maintenance is a bit more intense than on the 454's, and when replacement parts are needed, they will be more costly, however with th eproper maintenance, there is less repairs to be done.

No ignition components, computers or sensors to fail.

Less chance of explosion/fire.

Cruising efficiency with the 454's was .65 - .78 NMPG at 15 kts

With the Yamars it's 1.3 - 1.55 NMPG at 20-22 kts

Diesel fuel is generally 15-20% cheaper than gasoline.

My Yanmars are smaller and lighter than the 454's they replaced. There was no shoehorning necessary. 1/2" aluminum engine beds were throughbolted to the stringers to reinforce for the additional torque

The 10 Meter International had 8.2 Detroit Diesels as an option.

I had a new survey done priorto pulling the 454's to insure the integrity of the vessel and the survey was completed after the installation to certify the refit and the value for insurance purposes.

I also replaced the HVAC, water heater, various 25 year hoses, etc and rebuilt the sanitation system.

The design and engineering of the 10 meter International made her a worthy candidate for this refit. Doing this to a 33' Maxum. Wellcraft or Sea Ray would not be a good choice.

This boat is now totally reliable and functions as new at a much lower cost.

With some new upholstery, corian countertops, sink & fittings along with some new LED lighting in the forward cabin, the result will be a new boat.

Her timeless, contemporary styling is an additional plus.

RWS