may i ask ?
 

i am sorry about all that i ask but somehow i get to learn
and such a questions only experience can answer
you dont find theme out there...so.
whats the difference between Gas and Diesel engines besides
fuel:cool:
Performance is affected? do i have to get more horse power
if i get diesel
Please enlight me

In very basic terms: Diesels are simpler, more reliable, have better fuel economy, generate more torque, and have greater life expectancy than equivalent gasoline engines. However, diesels will be heavier and probably be more expensive than their gas counterparts.

gas engines rely on a spark to ignite the air fuel mixture. diesel engines use compression/heat to ignite the mixture. Gas engines need a certain octane to avoid detonation....diesel motors pretty much run on detonation, thus you can use all types of oils as fuel. Diesel fules have a much greater energy output than gasoline. Diesel motors are very strong and heavy and can make lots of torque at low RPMs and are well suited to forced induction like turbos b/c their top ends are bullet proof....but heavy. Unfortunately diesels dont turn high rpms so they must spin special props, usually through two speed gear boxes. In every concieveable manner diesels are better than gas. but they remain heavily built, and dont turn high rpms so they cannot be run with such precision w/o technology and multiple gears.

if i was to buy a 30 ft boat with
2 inboards mercruisers a200 turbo diesel
or
2 mercruisers 4,3 L 205hp
which should i choose?

If money didn't matter? The diesels. 1500-2000 hours later with regular maintenance they will STILL be going strong.

Not that this is a good comparison, but around where I'm from Gasser trucks are just about disposable after 5 years or so. If you aren't running an oil burner, you're wasting your time and money in the long run.

Boats need torque to push them through the water. Diesels make lots of torque, diesels are preferred. A 200 hp diesel is rated 200 at about 2500 rpms, a 200 hp gas motor is rated at 4500 rpms or so. If we know that horsepower is basically torqueX rpms then we see that a 200 hp diesel has almost twice the "power" of a 200 hp gas engine. A 200hp diesel would be faster and get better fuel economy in the same boat.

The diesel being havier doent mean that i have to get
biger angine with more horsepower
And
Isnt gas more dengerous on a boat then diesel?

By the time you get to 30 foot and twin engines, the weight is not as much of a factor. Yes gas is much more dangerous.

You have to consider torque, as in Ft. Lbs., it's not all about raw HP.


Diesel is MUCH cheaper than Gas (on the water that is) In most cases over a dollar a gallon around here. You will get much further on a gallon of diesel than you will on that same gallon of gasoline too.

Diesel is not combustible like gas, throw a match in a 5 gallon bucket of diesel and it will go out. Throw a match anywhere NEAR a pint of gasoline and you are in trouble.

The only problem is the diesel motor will need something between it and the prop to make it a performance boat motor. Wont you give up something by having a prop so steep that will turn you respectable MPH's at a WOT of only 3200 rpms? Thus the need for multi speed gear boxes? I would think the massive torque of a diesel motor would allow this without a sweat.