OXE Diesel Outboard Experiences?

[IronPrice]

Does anyone have experience of using these outboards? Specifically about their durability, noise and vibration characteristics they are.

Background
I'm currently having a design done for fast work boats that will have twins jets units powered by twin diesel inboards. The twin config is for maneuverability and the jets are for easy (i.e. diver-less) disentanglement, which are a regular hazard in the work the vessel is designed for. We're aiming for vessels that can cruise at 25 knots. The duty cycle would be 30% at cruise speed and 70% at slow speed.

It has occurred to me that I might be better going with 2 or 3 diesel outboards. They offer the operational advantages I'm seeking from jets but without being so horsepower hungry. Outboards are a lot easier to service than inboard engines. A power head could be swapped out in few hours (or a whole) engine if required. Mid-survey inspections would be a lot easier, because there would be no hull penetrations and therefore no need to pull the vessel out of the water.

Outboards would also greatly simplify some aspects of the design that are currently a problem, due the the amount of internal space occupied by the engines.

 

[comfisherman]

I don't have direct experience with one, but spent a fair whack of time in a similar situation. Maybe my line of thought can be helpful.

I do a short fishery 5-700 hrs a year that is best suited with a shallow outboard work skiff. We've tried jets and current use a combination of an old gas ob skiff and a jet. Gas is increasingly hard to purchase on the grounds while diesel is easily sourced. Jets are getting expensive as are diesel inboards, and jets have grass sensitivities that an ob doesn't have.

Local outfit sells the oxe and had a demo on a local small charter boat. They did a demo, must have been late 2019 as it was right before the world went Topsy turvey. It didn't seem any less behaved from a vibration or noise standpoint. Granted it was a short run in the harbor. What struck me was with the 1.39 ratio the prop selection did really seem to wow on the torque front.

At the time a suzuki was 21,700 installed and the oxe 59,800. Both are up a bit but the oxe is in the low 60s now. Idea of diesel outboard is nice, but it seems like in workboat scenarios it's still limited by the industry focus on 17 inch props. As such it's torque figures while impressive didn't translate pushed through the gear case.

While a jet+gear+ engine is likely more the lifespan of a 6.7 cummins at 300 hp is gonna be longer than a 3.0 block. Although probably double the weight.

I'm still in a holding pattern on a gas ob vs. Diesel ob vs building another jet. Nursing along an old boat waiting my peers to run out of stimulus money before competing for build resources. At double the cost it probably would have sold me, but it's closer to 3x. Interesting enough to my knowledge they have not sold one yet in my local.

 

[IronPrice]

We won't be running much shallower than about 2m but we will be in and around mussel farms. Props picking up ropes is a recurring problem. We have line cutter on our shaft driven vessels, but occasionally we need to get divers in to untangle props.

Our choice of inboards is quite limited, because we are working with a low bilge height. and engine have to be matched to jets quite carefully. Gasoline isn't an option in our operation - we've eliminated it (and LPG/Propane) from all vessel operations, due to the fire hazards.

 

[fallguy]

I considered them briefly for my OB cat to get away from or reduce the greatest risk to the boat, which is fire.

I could not get past two issues. One is the dual crank. I understand the purpose, but in my head it is another point of failure AND at 3x the cost of gasoline; I could not get to appreciating it enough. For a recreational vessel, it did not make sense. But it might make sense for a workboat used daily.

I'd be a bit nervous about meeting your speed requirements as others have stated more eloquently.

And you'll need to be careful about their weight.

 

[comfisherman]

Sounds like it could work for you then. While 300 hp out of a 3 liter is a lot for diesel power, I'm not sure your going to be able to prop it heavy enough to overload it. Pure conjecture but I'd guess the lifespan is in the vicinity of other power options.

If it was my money I'd press hard on my regional sales guy to get figured on how many are in the wild near you. Everything will need parts eventually and if you own an orphan that can mean a long frustrating wait.

 

[IronPrice]

Sounds like it could work for you then. While 300 hp out of a 3 liter is a lot for diesel power, I'm not sure your going to be able to prop it heavy enough to overload it. Pure conjecture but I'd guess the lifespan is in the vicinity of other power options.

If it was my money I'd press hard on my regional sales guy to get figured on how many are in the wild near you. Everything will need parts eventually and if you own an orphan that can mean a long frustrating wait.

We're building three identical vessels, so we would be buying either six or nine engines (the designer hasn't done the maths yet).

Our inboard supplier keeps a spare engine and an agreed list of parts in NZ just for us, so I'd be looking to negotiate something similar.

 

[powerabout]

One came to Singapore for a 23' charter fishing boat.
Dealer bought it back said another one will be the same, so sorry
Dealer was pretty much at the Marina every other day for a few months
IMHO just not ready for production
Non stop trivial but spoil your day issues
I witnessed one that the owner had complained about, start from cold and it goes to 200o rpm all by itself

 

[BlueBell]

IronPrice,

Are you considering the 200HP or the 300HP?
USD$90K each for the 300's!

I found lots of info on YouTube two weeks ago.
The 300 uses a BMW engine.

 

[DogCavalry]

@IronPrice , have you considered surface drives?

 

[DogCavalry]

One came to Singapore for a 23' charter fishing boat.
Dealer bought it back said another one will be the same, so sorry
Dealer was pretty much at the Marina every other day for a few months
IMHO just not ready for production
Non stop trivial but spoil your day issues
I witnessed one that the owner had complained about, start from cold and it goes to 200o rpm all by itself

When was this?

 

[IronPrice]

@IronPrice , have you considered surface drives?

To fragile and too much entanglement vulnerability around mussel farms.

 

[BlueBell]

Are you considering the 200HP or the 300HP?

???

 

[IronPrice]

???

Sorry I missed your post.

I don't know yet. My gut says we will need quad 200s or trip 300s. The naval architect is doing the numbers this week, as going from jets to outboards changes quite a lot about the vessel design. Given the chocie of quads or trips, I'd probably go for trips, to get the outside props further form the sides of the vessel.

The main concern I have with the jets is how weight sensitive they are, and the amount of HP required. No such issues with diesel engines.

One downside of outboard: I would need a separate auxiliary engine, for hydraulics and domestics but that won't be a biggie. Probably a little Kohler genset and an electric powerpack for the hydraulics would do the job.

 

[DogCavalry]

To fragile and too much entanglement vulnerability around mussel farms.

Wrong on both counts. Unless you're thinking Arnesons. Don't know about those. But surface drives can be arbitrarily strong. And the least susceptible to entanglement of any prop type.

 

[IronPrice]

Wrong on both counts. Unless you're thinking Arnesons. Don't know about those. But surface drives can be arbitrarily strong. And the least susceptible to entanglement of any prop type.

A few mussel farmers here have tried surface drives. They've all ditched them. Because of breakages and entanglements.

Mussel farm structures are widest at the surface. Therefore, a propellor is most vulnerable to entanglement at the surface. A surface drive also protrudes aft of the vessel, and the rudders are either outboard of or aft of the props. Unless the whole drive pivots which is a very fragile setup. It's all very vulnerable. Something can always be made stronger, but then you get into bigger components and things get oversized fast.

I'd go with jets over surface drives.