Diesel outboards

[Boatman1011]

I also don’t think you can compare the older 2S outboards to the new common rail Diesel engines. Realize even the current 4S emissions technology represents emissions levels the automotive world was achieving back in the late 70’s and early 80’s. The marine regulation for marine Diesel engines is Tier 3 which does not require after treatment or DPF’s. That technology starts with Tier 4 which is the larger products for yachts and cargo shopping vessels. Here’s an image that shows the difference in emissions output from the “clean” 4S petrol outboards compared to the EPA Tier 3 diesel reg.

 

[powerabout]

any photos of the belt drive to the gearbox, I wonder how long that lasts?

 

[Boatman1011]

Here’s a video

 

[Boatman1011]

One more

 

[ondarvr]

https://www.facebook.com/share/p/18MhRFxCru/

"We've been getting a lot of questions so we figured this post was long overdue. I'll try to keep it short because a lot has happened.

After arriving in our home port April 2023, almost immediately we experienced multiple disappointing and unsafe engine issues and failures with the OXE 300hp diesel outboards, 6 complete engines, plus one powerhead to be exact. Yes, 7 engines in total! The two engines that were hung on the back of the boat when it was built by ACI, died within 5 months of arriving in Newport OR. Then, working directly with OXE Marine they continued to install 4 more new OXE 300hp diesel outboard engines, a new 300hp diesel powerhead, modified and replaced multiple hoods, numerous other parts and multiple turbos, which all suffered the same fate.

We gave OXE Marine every opportunity to make their engines work as advertised. We even let them modify our boat by cutting multiple holes in the back of the boat and on the deck for snorkel tubes and hull ventilation, hoping they could make it work, but nothing they did or tried to do worked.

After the last two engines had serious issues at sea June 2024, we decided that was enough. We needed to move on to something safe, reliable, and something with the power to move the boat through the water. After failed negotiations with OXE Marine and ACI to stand behind their products and warranties. We decided we would have to take the next steps on our own. We made the bold decision to purchase a pair Mercury Verado V10 400s, which have been AMAZING! We've had multiple successful overnight tuna trips and have hundreds of uninterrupted hours of run time without a single alarm going off or hiccup, literally not one single engine related issues or break down. We now have the safe, reliable, and fun boat we expected, it's just really unfortunate we had to do it ourselves and spend a lot more money.

Overall, the Oxe diesel outboard venture, for us was a complete failure and a major disappointment. We gave them so many opportunities to fix the situation but nobody wanted to step up to the plate and take care of us."

 

[comfisherman]

Looks like a less litigious resolution than the one local to me. Know 4 went on, 4 came off and nobody is talking while lawyers work out the details....

 

[DogCavalry]

So this seems to be the current state of the art. Unless there is a more recent update.

I suspect there's nothing intrinsically wrong with the concept. There just aren't enough sold to generate the cash flow to pay to work out all the bugs. We all know diesel inboards work well, although the maintenance cycles are expensive. With the increased cost of diesel fuel, maybe they have lost their economic advantage?

J

 

[fallguy]

So this seems to be the current state of the art. Unless there is a more recent update.

I suspect there's nothing intrinsically wrong with the concept. There just aren't enough sold to generate the cash flow to pay to work out all the bugs. We all know diesel inboards work well, although the maintenance cycles are expensive. With the increased cost of diesel fuel, maybe they have lost their economic advantage?

J

The reason I moved away from them was two things:

1. Cost was way too high.
2. An extra crankshaft meant complexity was increased which means maintenance cycles increase; not decrease. It is not complex; it is basically like two engines under one hood.

I think the real problem is we assume diesels have lower maintenance, but it is not rational for these outboards, and they are proving it.

 

[HelmutSheina]

Parsun recently introduced 150, 175 & 200hp diesels.

D200 Diesel Outboard Motor Wholesale

The D200 Series Diesel Outboard is Parsun Power’s flagship product, built on 22 years of engineering expertise. It combines powerful performance, exceptional fuel efficiency, and superior reliability. Powered by an L4 turbocharged engine with high-pressure common-rail injection and closed-loop...

www.parsunpower.com

 

[DogCavalry]

Parsun recently introduced 150, 175 & 200hp diesels.

D200 Diesel Outboard Motor Wholesale

The D200 Series Diesel Outboard is Parsun Power’s flagship product, built on 22 years of engineering expertise. It combines powerful performance, exceptional fuel efficiency, and superior reliability. Powered by an L4 turbocharged engine with high-pressure common-rail injection and closed-loop...

www.parsunpower.com

Holy cow! Closed loop cooling with heat exchanger. The holy grail...

If it is reliable, it wins the world

 

[HelmutSheina]

Yes, surprised me too. Three gearboxes mentioned for an inline engine, love to see a diagram. Mind you, I've seen diesel outboards come out since the 80s and none have been the Holy Grail yet, all disappear after a time.

I have a small Parsun 4 str petrol tender motor and it has been a mighty mite. The only problem so far has been remembering to top up the tiny fuel tank as it lasts a long time.

 

[HelmutSheina]

The reason I moved away from them was two things:

1. Cost was way too high.
2. An extra crankshaft meant complexity was increased which means maintenance cycles increase; not decrease. It is not complex; it is basically like two engines under one hood.

I think the real problem is we assume diesels have lower maintenance, but it is not rational for these outboards, and they are proving it.

Which ones have two cranks? I have yet to see a diesel outboard that isn't inline. Do they have a balance shaft perhaps?

 

[montero]

High speed ratio to high for a diesel .

 

[fallguy]

Which ones have two cranks? I have yet to see a diesel outboard that isn't inline. Do they have a balance shaft perhaps?

Yeah, balance shaft. Pretty sure OXE bought out another design, but I don’t recall well anymore as I lost faith in them fully after reading some real bad reviews.

Our experiences with OXE Marine | In The Same Boat

OXE Marine left us with "dead" engines and a financial loss of more than 300 000 EUR. Update 11. of April 2026With help from Suzuki, we have finally gotten one of our OXE boats (“Crush”) back on the water after nearly three years out of service. It has been a challenging process. We are still

www.inthesameboat.eco

 

[DogCavalry]

The power to weight ratio of a typical marine diesel precludes installing one as an outboard: too much weight on the transom/bracket.

So the designers use lighter blocks leading to higher stress and strain, making parts vulnerable.

To increase power supercharging can be used, either with a mechanically driven blower, which gives a limited amount of boost and hurts fuel efficiency or by inserting a turbine in the exhaust stream to recover energy to drive the blower. This is complex and expensive, with hot assemblies inside the cowling leading to parts vulnerability. And since an outboard is, of necessity, a wet exhaust engine, there's water in the exhaust system. Turbo go boom sometimes.

Diesels inherently vibrate more than gasoline engines. So parts fail. I understand that failing wiring harnesses was a constant problem in at least one common brand.

Loads within the engine can be reduced by reducing the compression ratio, but that reduces power and fuel efficiency, and increases emissions.

All of these issues are solved the same ways: more robust parts that are larger and heavier, or made with more sophisticated materials that are dramatically more expensive. Or extremely developed and matured designs that need long, extremely expensive r&d cycles.

It all leads to what we have now: large, heavy, unreliable diesel outboards that cost two or three times as much as the equivalent gasoline engine, which is not a winning combination.