boatchris

hi u all in 1987 thur 1989 i install two diesel engines in two 46'
scarab 3208's 450 hp did 68 mph and 3116 310 hp cats in a 38' did 56 mph

HabanaJoe

We've run both stern-drive and Arneson. I found you run the Arneson boat just like a big boat, steer until your going to dock and then the engines to steer, it was quite responsive - no problem. For slow speed use trolling valves or 2 speeds.

You know that has to do with how close the engines are, if they're close it won't spin so easy with the engines.

The sterndrives are more complex, which is faster???

Back in 1989 there was a Don Shead UIM 2 boat (can't remember the name, Shell oil sponsored) that ran the number 4 drives 1:1 with overdrive gear boxes, it was a very cumbersome set-up. But, that boat could fly and could beat the EBEL speed wise and she had Buzzi drives. So which is faster, too many variables to say?

What kind of speed, is a function of having enough HP to spin a prop fast enough to go as fast as you want to go. Our pleasure boats could run 75-80 and race baots went over 100 in 1990 with diesels.

I'm not trying to be smart here but fuel consumption is a factor of HP being used to travel at a given speed.

I'm sorry it's taken so long to respond, I needed to find the dyno sheet that is attached here. In the old days when we did not have computers on the diesel engines in the boats, we took reading on paper and came back to the dyno and tried to mimick those to see how much power was really being used.

The sheet shows very clearly how much power was actually being used in the boat. These were 380hp Cummins B's on the dyno, not 1 hp less. The boat used no more that 325 hp at WOT and that is at around .31lbs/hr or 14 gal/hr. So, a 40' 17,000 lb boat cruising at 50 mph burned maybe 28 gal hr worse case.

The boat was a 40' Super Hero (Midnight Express lengthened) w/ Arneson drives, 1:1 gear and almost 4,500 in lead mounted midship to replicate the turret and weapons weight.

I'll make one point to all of this, to go fast like a gas boat your prop speed needs to equal that of the gas boat. Prop size can not compensate for prop speed. You need to spin the prop at it optimium speed however you do that.

h2owarrior

I think there was also a boat called "Drambui on Ice" that was equipped with 4 x 3176 Cats I actually have a poster of the boat.

Problem with most diesels is the weight........3208's although a very strong, reliable engine, weigh a ton.

I think Yanmar has a good light weight diesel package that would work well in a perfomrance boat. Problem is the tourque a diesel engines put out.....requires a farily robust system behind it.

Didn't Jassman have a Nortech Equiped with diesels ?

h2owarrior

It's an energy thing. The efficiency comes in for the diesel as diesel fuel has more BTU's per pound than gas. So to produce the same power over a given period of time, you burn fewer gallons.

Dawg Gone

On a 24' Whaler Outrage, a 225 Optimax burns 22.1 GPH and moves it 41 MPH (their numbers not mine).

The surface drive - diesel combo is one heck of an efficient set up compared to the single outboard on a much lighter craft.

Quick math says 1.78 MPG for the twin diesels and 1.93 for the outboard.

How much do the surface drives contribute to the overall efficiency?

frogger1403

Hustler quite a lot Diesel powered boats. They will show a Diesel 38 in Miami, their P1 race boat is diesel powered:
http://powerboatp1.com/public/team.asp?team_id=11

There also have been some 50' and 26' diesel boats.

heiko

jordy

Of all the diesels to pick, why on earth would you suggest the heavy slug of a 3208??? Not only is that a monster weight wise, a slug performance wise, but it's also about the dirtiest diesel you could ever possibly want to run.

Imco has been testing a Duramax that was marinized in a Nordic and has had amazing results. I've often thought about picking up a Top Gun, less power and rigging it for diesels. The down side of everything has always been finding drives that will hold up to the power. That's the upside of diesel engines on the road, the incredible torque curve, however, on the water, a 300hp diesel with a 700 ft. lb. torque curve is going to be hard on drives in a big boat.

Yanmar does make some great marine engines as well, and seeing how I work for a Yanmar dealer, that was choice number 2.

Dean Ferry

http://www.mysticpowerboats.com/boat...700/index.html

Diesel power in a 70', 60,000 lbs. boat that does 80+ MPH, Plus Callan's 65' v-bottom does 95MPH, that sounds pretty high-performance to me!
Dean

HabanaJoe

Dawg Gone

I believe the boat ran as well as it did because of the surface drives with large dia porps.

The patrol boats were never designed to run over 60 mph, they were designed to cruise at 50 mph for thousands of hours.

You could never get an outdrive to last that long without more maintenance that you would have done to an Arneson.

In order to swing the same dia props you would have needed number 5 or 6 drives. I don't remember exactly but the weight of those were greater than an Arneson plus to be as efficent they would need to be mounted rather high would would hurt low speed plane.

Swamplizard

did a bunch or research on repowerring my 15000 lb 43 footer with ASD8s.....issues I came up with were as follows:
1) Price - to do it right with lightweight diesels that could fit meant using Yanmars or Staers .... $40k/side plus props, tank and fuel line changes...$100k. For $100k you can build a bunch of 600hp gas engines.
2) Weight - diesels typically weigh twice as much as gas engines so you better be able to float it, have the stringers to support it
3)RPMs - tough to get the right rpms out of them - they rev low compared to performance gas engines so trans needs to be 1:1 or 1.2:1. BTW Diesel capable gears also weigh a lot compared to gas versions.
4) They are designed to run at 90% of their WOT and dont do well otherwise - this means you will have a boat that does 8mph and 80mph...nothing in between efficiently...gas power you have more flexibility rpm range-wise to adjust to the conditions you are running in
5) Need to re-rig to handle twice the heat and twice the water flow...diesels need tons of water to keep them alive and exhaust can't be restrictive so you need all new plumbing ...some layouts have a hard time accomodating water cooled 12-inch diameter exhaust tubes in the engine room.

Upsides - twice the range, sometimes twice the hours between builds, safer since diesel doesnt blow up, and down here you can get dockside fuel delivery if it's diesel...nice!