Are marine engines getting more efficient

[oldgit]

All below at mainly pottering type speeds with odd whizzy spells.
Princess 25 (3 tons ?)single V6 petrol approx 5 gallons per hour/forums/images/icons/frown.gif
Princess 33 (8 tons) twin 6 cyl diesel approx 2 gallons per hour/forums/images/icons/smile.gif

Oooh look its still not dark and its nearly 5pm

 

[Guest]

That is some difference, is it reflected in the cost of a diesel engine in the secondhand market. e.g. do the diesel's still keep their pro rata price difference from initial purchase.

 

[spannerman]

Hi Brendan, I just read your profile to see what rig you had, and wondered what prop do you have? And you have Bravo drives, yes? Just curious as to why your trim is so sensitive.

 

[BrendanS]

Uhhm! can't remember off hand what the prop is, and it's an alpha leg
Trim is sensitive because of the hull. It's high performance, with multiple steps, laminar flow interrupters, and all sorts of clever tricks. Upshot is that the water under the hull has a huge amount of air introduced into it, which means it susceptible to ventilation if you don't get the trim right. Design of the hull means that you don't require all that much trim compared to most boats, and doesn't gain much either. Gain a knot or two in flat calm, flat out.

<A target="_blank" HREF=http://www.regalboats.com/>go here</A> and click on the fastrac box to see what it looks like. Lots of marketing hype, but people in my club will tell you it works great /forums/images/icons/smile.gif

 

[andrewa]

I think Old Git and Spannerman are better replying to that question.

1) If you want diesel power buy a diesel boat it works out cheaper in the long run unless boat is dirt cheap and then check to make sure it can take a sensible size diesel or diesels mine can't, the engine area is to small it was designed for petrol so not enough length for anything over 4 cylinders.

2) Repower is expensive full stop, i.e 240 yanmar all the bits fitted £19k now thats a hell of a lot of petrol even at marina prices. Boat would be worth around 10k more I reckon with it and the performance would suffer, servicing dearer though would be easier to sell come trade up time.

3) Repower with another petrol i.e 270hp 5.0L MPI from V^*_%, fresh water cooling, duo prop with props new controls, lifted tested fine tuned, should do around 2.5mpg at cruise approx £9k all in. Boat will be worth more in 3 years come resale time by about 2-3k I reckon should also sell bit easier with a newer power train. The mention of a 7.4L and people tend to run a mile. Servicing is cheaper to.

Now just to complicate things hours come into it if less than 100 hours a year I think petrol would probably win the day. Over that you need to do some sums and also work out how long you want to keep the boat for taking into account the above.

I got into this because my engine good but Bravo drive is on last legs. To have a new bottom end (just bottom not whole drive) and props for Bravo III is £4600.00 incl vat and fitting and a pre-season service. Bravo II around the same though save around £500.00 in props.

Now you see my dilema Grumpy. Welcome to the world of boating.

 

[spannerman]

Yes, if you check used boat prices a version with a diesel engine will always be higher priced than the same boat with a petrol engine, so you will recoup some of your investment. However if you are doing 100 hrs p.a. or less a petrol boat is cheaper than a diesel, when you consider initial purchase, fuel costs, loss of interest on the money spent and resale value after 5 years. We are talking new boats here, but the price differential carries across the board, so you pays your money and takes you pick.

 

[Guest]

Interesting, thanks,

 

[hlb]

We have been through this argument hundreds of times. Nowt wrong with petrol as long as. Go out from same place and back. As Long as it has petrol of course. And with small boats this is fine. Cos cant go any further. But with bigger boats it is just not an option. Dont matter how many pounds you have in pocket. No Petrol. Zilch. Where as with diesel you can buy borrow or beg some from any passing Fishy boat, Tanker or depo. They wont let you down/ drown. Just pull into any harbour. I dont mean poncy Solent type. Proper harbours, only found now round Ireland, Lancashire Or Scotland. Wales maybe. But their a law unto themselves!! If stuck. Ring the local heating oil co. He will fill you up. No problem. And give you a better deal.

<font color=blue> Haydn

 

[BrendanS]

Not as convenient I'll grant you, but you can actually go long distances in petrol boats. Just have to plan more, and be prepared to do several tedious trips to local petrol station with cans (which can often be borrowed from harbour master or marina)

I'm hoping to go quite a way afield this year, now I've lost the missus, and the lack of generally available petrol won't stop me. What would stop me is single handling a big boat.

Horses for courses and all that

 

[duncan]

trim....

please do not forget that you have to use engine trim in conjunction with hull weight distribution for a boat your size. This can have an significant impact on all of the performance attributes being highlighted in this post but has not had a mention!
On a good boat the fuel tank will be at the centre of gravity the designers want to achieve and you can work around that but beware boats offerred with both shaft and stern drive on the same hulls as only one position will be right!