New bottom paint- New diesel outboard

[Alan Waters]

https://newatlas.com/anti-biofouling-ship-paint/52471/
https://newatlas.com/yanmar-dtorque-...utboard/51675/

[ggray]

That's cool!

Two cranks and connecting rods for each piston.

[a64pilot]

At almost 400 lbs is HEAVY, but interesting, wonder if the dual crank is really necessary, could a counter balancer have done mostly the same job?

The real question though is what will it $$$?

[valhalla360]

Interesting but some sketchy stuff:
- Double the life is pure speculation. Plus most motors die from poor maintenance not wearing out.
- All of the graphs, don't show performance for gas engines below 3500rpm. It should go down to at least 1500 if not lower. Are they hiding something?
- For the small overlap in the fuel consumption graph, the gas engines win. Diesel should win by 20-30%. Especially since the gas engines being compared are higher HP. (really it should be a direct comparison on test boats at specific speeds as RPM by itself doesn't directly correlate to fuel consumption)
- They claim it is lighter at 175kg but a new Honda 50hp specs at 97kg. Even if the honda spec doesn't include remote controls and such, it's still much lighter.

I liked the idea of the old Yanmar diesel outboard for a displacement cruising boat where weight didn't matter but you got the advantages of a both an outboard and a diesel but 50hp isn't a commonly needed size for displacement outboard powered boats. For small planing skiffs, the extra weight is a strong negative.

The other issue is who is going to work on these? It's an oddball item.

[hobopacket]

Is horse power really a good comparison between diesel and gasoline? I would the torque at certain rpms versus engine displacement and Economy would be a better stat for comparison. For instance, my tractor at work is only 115hp but it’ll pull a hell of a big load.

[valhalla360]

Originally Posted by hobopacket

Is horse power really a good comparison between diesel and gasoline? I would the torque at certain rpms versus engine displacement and Economy would be a better stat for comparison. For instance, my tractor at work is only 115hp but it’ll pull a hell of a big load.

Torque X RPM = HP

Since most boats get up to speed and then stay at that speed(displacement or planing), they need a certain HP to maintain that speed. So for a specific HP, you simply adjust the gearing to get the desired RPM & torque at the prop.

For planing boats, the heavier weight really hurts the diesel acceleration as it will struggle more to get on plane.

Your tractor may pull a big load but won't do 75mph pulling that load. That's why semi-tractors have a lot more HP than your tractor. If you want your 45' sailboat to have a cruise speed of 3kts on a calm windless day, you can get a away with an amazingly small HP engine (7-10hp might do it) but if you want to run at hull speed against a strong headwind, you will need a lot more HP (probably in the 40-60hp range depending on exactly how strong the wind is).

Economy is a good stat and diesel should win but what they gave us is a fairly poor way to compare and shows the gas engines doing better (but most of that may be the very poor way the data is shown). They should have shown a comparison of HP output to fuel consumption as a start but even better would be to do it with identical test boats compared at specific running speeds.

[a64pilot]

The BSFC of the engine would tell the tale, and they certainly know what it is, but marketing is not run by the Engineering dept.
HP and Torque are the same, or are inseparable if you had rather see it that way.
All dyno charts have the HP and torque curve converging at 5252 RPM.
Some motors make power at low RPM and others at higher RPM, forced induction is an excellent way of making a motor make power at lower RPM.

My 50 HP tractor would pull my 200 HP four wheel drive truck backwards, but that had to do with traction, not torque vs HP.

[a64pilot]

Mercury has had a strange Diesel outboard for years I think, but I believe only sells it to the Defense dept.
It’s strange cause I think it’s a spark ignition motor, that burns Diesel fuel, so it’s not a real Diesel.
Lycoming has also built a small JetA fueled spark ignition motor as well, I think.

[a64pilot]

Perhaps a Diesel fuel two stroke outboard may be what we want?
http://www.mercuryracing.com/optimax...ting-for-duty/