TT35 at the Annapolis Boat Show

[Woodland Hills]

Originally Posted by OldDan1943

I am not pleased.
Why not diesel outboards?

Because they are heavy, expensive and vibrate like paint shakers?

[IronZebra]

The torque of the new 50hp diesel Yanmar Dtorque 111 looks like it may push this as good as the 60hp gas Suzuki. The two-counter-rotating crankshafts are very interesting design.


Here is a really good article on the Yanmar published couple weeks ago. https://newatlas.com/yanmar-dtorque-...utboard/51675/

Yanmar description.
YANMAR LAUNCHES THE DTORQUE 111 TURBO DIESEL OUTBOARD - Yanmar Marine

[Miz Trom]

At the very bottom of the Yanmar announcement:

*The Dtorque 111 exceeds EU RDC Stage 2 emissions regulations, however is not EPA compliant.

[DavidM]

I read the article and I guess I can buy most of Yanmar's claims for this engine, except for being lighter than an equivalent gas outboard. Unless they mean equivalent being a 90 hp 2 cycle O/B to produce the same torque as the 50 hp Yanmar at 2,500 rpm. But gearing on a 50 hp gasser solves that easily and saves about 100 lbs.

David

[ben2go]

Interesting design for sure but not anything new. If I remember some of the engine histories correctly, there was some testing of gas engines using the same dual crankshaft set up between WWI and WWII. I don't really see how it could be lighter unless they are comparing torque specs at certain RPMs. The diesel will have a lot more torque lower in the rev range that any gasser, 2 or 4 stroke. As mentioned by djmarchand, it wouldn't be fair to compare weights based strictly on max horsepower ratings. Comparing weights based on torque ratings may bring them inline a little better. I still feel the same as djmarchand, I think the new efficient two strokes would be a better engine as far as weight to HP ratio goes.

[Nomad Willy]

A very interesting aspect of this design is that the significant side load on the piston is basically gone .. nada.

However one can’t get away from the torsional vibration of a two cylinder engine. This vibration is prominent at low revs but quickly disappears as rpm increases.

Another source of vibration occurs from what the engineers call a “rocking couple”. That is a result of one piston (+ rods and crankpin) in the vicinity of BDC is pushing the crankshaft down while the other cylinder near TDC is feeling a strong upward force as that cylinder reaches TDC. One end of the crank up .. the other down .. and attempting to rock the crankshaft this way and that or back and forth. Counterweights can only danpen out some to most of this vibration input depending on other aspects of the design. So one can’t escape all of this source of vibration.

A friend of mine reports a small dual crank (sailboat) BMW engine that runs very smooth. More evidence of the fact that it’s not new. But I’m fine w old stuff and it’s anything but that.

[ben2go]

Originally Posted by Nomad Willy

A very interesting aspect of this design is that the significant side load on the piston is basically gone .. nada.

However one can’t get away from the torsional vibration of a two cylinder engine. This vibration is prominent at low revs but quickly disappears as rpm increases.

Another source of vibration occurs from what the engineers call a “rocking couple”. That is a result of one piston (+ rods and crankpin) in the vicinity of BDC is pushing the crankshaft down while the other cylinder near TDC is feeling a strong upward force as that cylinder reaches TDC. One end of the crank up .. the other down .. and attempting to rock the crankshaft this way and that or back and forth. Counterweights can only danpen out some to most of this vibration input depending on other aspects of the design. So one can’t escape all of this source of vibration.

A friend of mine reports a small dual crank (sailboat) BMW engine that runs very smooth. More evidence of the fact that it’s not new. But I’m fine w old stuff and it’s anything but that.

In the motorcycle world, the parallel twins are getting offset crankshafts instead of being true 180 degree crankshafts they are getting some offset to help with the one up one down vibration syndrome. I think my 2014 Honda CB500X uses this type of crankshaft. It is exceptionally smooth through out the rev range and I think Honda uses it in the outboards as well.

[Nomad Willy]

Ben,
Yes Honda is an innovator to be sure. I liked their offset crank outboards.

Wonder how many degrees off 180 degrees they are .. like a little or a lot. On the old Brit bikes the rocking couple presented a heavy buzz like vibration at hwy speeds. But were smooth at lower rpm. The Honda 180 degree cranks of the 60's were (predictably) more like a single than a twin. On a boat I think I"d like the 180 crank. Spend about 95% of our time on boats at cruise rpm.

[ben2go]

Originally Posted by Nomad Willy

Ben,
Yes Honda is an innovator to be sure. I liked their offset crank outboards.

Wonder how many degrees off 180 degrees they are .. like a little or a lot. On the old Brit bikes the rocking couple presented a heavy buzz like vibration at hwy speeds. But were smooth at lower rpm. The Honda 180 degree cranks of the 60's were (predictably) more like a single than a twin. On a boat I think I"d like the 180 crank. Spend about 95% of our time on boats at cruise rpm.

I'm not sure how much off they are. I don't think it has to be much, 10 degrees or there abouts.

[Nomad Willy]

OK Ben it soulds like they are close to a 180 crank. The only succesful 180 crank engines I know of are the old Brit bikes. They all had massive crankshafts (to ballance the counterweights to the pistons) so I’m going to guess this new engine will pay a weight penalty w a heavy crank. Looks like the pistons and rods are heavier too. And there’s two wrist pins on the piston and that adds to the weight but if it were a single wrist pin it may be about the same total weight ? So the chance of this engine being comparatively light is low or less.

But the high torque they get from only two cylinders is golden. I see it’s 50/50 bore/stroke. Makes for a compact engine too. I see the chain driven cam drive in-between the cylinders adds to the compactness. Many motorcycles are driven thusly.

Makes me wonder if a boxer engine w the two crank arrangement would have even more advantages. Food for thought.

[ben2go]

Originally Posted by Nomad Willy

OK Ben it soulds like they are close to a 180 crank. The only succesful 180 crank engines I know of are the old Brit bikes. They all had massive crankshafts (to ballance the counterweights to the pistons) so I’m going to guess this new engine will pay a weight penalty w a heavy crank. Looks like the pistons and rods are heavier too. And there’s two wrist pins on the piston and that adds to the weight but if it were a single wrist pin it may be about the same total weight ? So the chance of this engine being comparatively light is low or less.

But the high torque they get from only two cylinders is golden. I see it’s 50/50 bore/stroke. Makes for a compact engine too. I see the chain driven cam drive in-between the cylinders adds to the compactness. Many motorcycles are driven thusly.

Makes me wonder if a boxer engine w the two crank arrangement would have even more advantages. Food for thought.

[Donsan]

Did the owner of Spirit Song (hull #2) take delivery?

Sorry, can't seem to find their blog anymore and no mention of it on the GH web site.

[OldDan1943]

If people are concerned about the vibration of a 2 cylinder diesel, I'd bet they really get excited with a 1 cylinder diesel or one cylinder gasoline engine.

[OldDan1943]

When timing a 2 cylinder steam engine, one adjust the slide valve of the 2nd cylinder opens as the other valve closes. Unless perfect, sometimes one must give a bit of help with the flywheel.
Same way with the old farm tractor engines, spin the fly wheel to start the engine. Sometimes it had a duel fuel system, start the engine on gasoline and when running, switch to diesel.
Gosh, am I showing my age again?

[ben2go]

Originally Posted by OldDan1943

If people are concerned about the vibration of a 2 cylinder diesel, I'd bet they really get excited with a 1 cylinder diesel or one cylinder gasoline engine.

Those engines don't vibrate. They dance all over the bed, the engine bed.

[BandB]

Originally Posted by Donsan

Did the owner of Spirit Song (hull #2) take delivery?

Sorry, can't seem to find their blog anymore and no mention of it on the GH web site.

Last blog post in March. No updates on the TT35 that I can find on their site. Facebook doesn't indicate any deliveries taking place.

[OldDan1943]

Originally Posted by ben2go

Those engines don't vibrate. They dance all over the bed, the engine bed.

Yup, a little 'hit and miss'.

[Island Bound]

Originally Posted by Donsan

Did the owner of Spirit Song (hull #2) take delivery?

Sorry, can't seem to find their blog anymore and no mention of it on the GH web site.

As of the last post on October 31st, Spirit Song had not been delivered. Here is a link to the new blog:

https://oldmanriverandcoco.blogspot.com/

[Donsan]

Originally Posted by Island Bound

As of the last post on October 31st, Spirit Song had not been delivered. Here is a link to the new blog:

https://oldmanriverandcoco.blogspot.com/

Can't imagine what the holdup is except for perhaps reworking the swim platform and raising the cockpit.

[IronZebra]

FB page says took delivery on Nov 17.

https://www.facebook.com/greatharbourtrawlers/