Re-power Flying Dutchman FD-12

[Hoghead]

I am thinking of re-powering my Flying Dutchman FD-12, currently fitted with a Ford Lehman 80.

Beta Marine engines are attractive to me as I like the reputation of Kubota, and luckily there is a Dealer here in Subic that can land the engine in the Freeport Zone tax and duty free so it is competitively priced

Beta have a non-turbo, mechanical injection, mechanical lift pump, mechanical governed, 90 Hp engine that is appealing for the simplicity factor. Not emissions rated, but not an issue here.
Then again less power is cheaper, but the last thing I want is to be underpowered

The boat has a Maxprop, which will help in matching the engine power curve.

Beta have not replied on what engine would be most suitable, and the Dealer does not have the experience to advise
Has anyone re-powered one of these boats, and if so with what engine and at at what power level?

The other half of the re-power question has to do with the transmission. The FD-12 has a hydraulic drive consisting of a pump mounted on the engine, and a motor on the shaft, interconnected by a 12" long hose.
Motor and pump have about 1500-2000 hours

Even though labour is cheap here, the cost of adapting the hydraulic drive may well approach that of buying the engine ready to drop in. It will however be a bit trickier due to requiring alignment

Keep the hydraulic drive, or go to a new gearbox at the same time?
If a new box how to pick the appropriate reduction ratio?

[Hoghead]

I have decided to buy the new engine c/w gearbox and deal with the complications of aligning the engine.

It is down to the Beta 90 which is a NA, mechanical injection, mechanical fuel pump, no black box engine and a Yanmar 110 turbo

Yanmar is about 5000 USD more expensive, abiet more powerful

This is a cruising sailboat so the engine would be typically run at the top of the torque curve in cruising mode.

For the NA Beta 90 that is 1400 RPM (2600 max) 57 crank HP (52 at the gearbox output) at 3 liters/hr.

Yanmar max TQ is 2000-2200 RPM, about 10 HP more, and about twice the fuel consumption

Yanmar is physically smaller but both are smaller than the red lump they are replacing

Beta VS Yanmar?

Turbo VS NA?

Unless convinced otherwise, I most likely will adjust the MaxProp so that it is a little overpropped

[DougR]

When looking at sailboat propulsion, it can generally be stated that the larger and slower turning the propeller, the more efficient it will be. That logically means that one would choose the gearbox with the most reduction ratio possible as that allows the engine to turn the largest prop. However there are other considerations to be looked at, particularly in a repower situation where the design is already cast in resin.

Some things to consider:
- large diameter prop equals high drag under sail ( unless you have a folding or feathering prop)
- large prop diameter might not fit in the existing space
- high reduction ratio may require a larger diameter prop shaft

If we look at the Beta 90 in the FD-12 and crunch the numbers with various reduction ratios we can see that prop efficiency and thrust increases as the gear reduction ratio increases. It looks like this:

-1.5:1 reduction, 9 kts speed, ideal prop- 19x11x3, eff. 38% , thrust 1410 lbs
- 2:1 reduction, 9 Kts speed, ideal prop- 23x13x3, eff. 42% , thrust 1560 lbs
- 2.5:1 reduction, 9 Kts speed, ideal prop- 26x 15 x3, eff. 45% , thrust 1700 lbs
- 3:1 reduction, 9 Kts speed, ideal prop- 29x18x3, eff. 48% , thrust 1810 lbs

So the next step might be to see what diameter prop you already have (if you want to reuse it) or what diameter prop can be fitted and still maintain the recommended tip clearance, etc. That gives you an idea of where you stand on the range of reduction ratios. It may be that the gearbox in question offers ratios somewhere in between those I used, but the prop diameter will be similar.

The other thing to consider is the configuration of the gearbox in question. It seems that most of the boxes offered on the Beta 90 have a "drop center" of about 4" or 5" from the crankshaft centerline to the propshaft centerline. This means the engine will have to be lifted this much to get the propshaft and gearbox aligned. Is there room to do that?

Hopefully this will give you something to think about.

DougR

[Hoghead]

Prop is a MaxProp, 22" with external adjustable pitch.
Feathers while sailing and at 4500 USD, I am keen to reuse it.
One thing I am not clear on is if the MaXProp is both R and L hand rotation?
Beta engine rotation is clockwise when looking at the gear output, and requires a R prop

Several gear ratios are available as standard, with others as an option
Technodrive TM93 hydraulic at 2.09, 2.40, 2.77:1
PRM 280 hydraulic at 1.96, 2.94:1
ZF45 hydraulic at 2.20, 2.50, 3.00:1
ZF45A at 2.03, 2.43:1

Which is the best box, and at what ratio to suit my hull and prop?
Thrust calculation must take into account both hull shape and speed? This is a bit beyond me at this stage, and I would appreciate help from someone that knows.

Is there a calculation to determine prop pitch for this boat, at a given reduction ratio? While my prop is adjustable, it would be nice to have a calculated starting point.

In fact I have been looking at the gearbox output elevation on the PRM 280 and if I am reading the tiny drawing correctly is is 89mm or 3.5".
I have asked Beta to confirm, and if all gearbox elevations are the same

Yanmar OTOH has the KM4A2 gearbox output on a 7 degree down angle, and only 36.3mm (1.43") lower than the crank centre line - A lot easier to install
The ZF30 box is 90mm lower and virtually the same as the Beta.
The other Yanmar box is even lower, although on an 8 degree angle

Lots to think about, and unfortunately I have no experience in this and the Dealer doesn't have the foggiest.
I would really appreciate some help in making the right choice

[Hoghead]

Found the VicProp calculator which answers a lot of my questions:
https://www.vicprop.com/displacement_size.php

Also discovered that the ZF45A gearbox fitted to the Beta has a 8 degree down angle. Offset however is 125.5 mm or 5"

[DougR]

Beta 90
If you plan to use the 22" max prop, which I assume is a three blade prop, your best choice of reduction ratio will be something around 2:1.

Select the gearbox configuration which will most easily lend itself to fitting in the vessel, and then chose the closest ratio to 2:1 for that particular transmission.

For the various ratios which you have listed, the following pitch setting should be somewhere close to where you will want to start:

Ratio- 1.96:1 22 X 13.5"
Ratio- 2.03:1 22 X 14.3"
Ratio- 2.09:1 22 X 14.9"
Ratio- 2.20:1 22 X 16"

All of these ratios are close enough to each other that the efficiency gains or losses between them are insignificant.

Hope this helps.

DougR

[Bill Seal]

I know it's too late, but that hydraulic drive sounds like a great idea, bulldozers and graders use it, so it must be reliable..

[Jim Cate]

Yanmar is about 5000 USD more expensive, abiet more powerful

This is a cruising sailboat so the engine would be typically run at the top of the torque curve in cruising mode.

For the NA Beta 90 that is 1400 RPM (2600 max) 57 crank HP (52 at the gearbox output) at 3 liters/hr.

Yanmar max TQ is 2000-2200 RPM, about 10 HP more, and about twice the fuel consumption

Looking only at the above data, the Beta seems a clear choice: considerably cheaper, much better fuel economy (and that's kinda hard to understand), running at much lower RPM and IMO a better company to deal with at purchase and later in life. And Kubota based engines have a very good track record in yachts.

What's not to like? Both engines have more power than your Lehman, and the mechanical tranny will be more efficient than the hydraulic system.

Jim

[Hoghead]

Originally Posted by Bill Seal

I know it's too late, but that hydraulic drive sounds like a great idea, bulldozers and graders use it, so it must be reliable..

Less efficient than a hydraulic conventional gearbox, and much more expensive.

As I already have a thrust bearing due to the hydraulic motor being mounted on the shaft, it is a simple matter to use a U or CV joint jackshaft to join the thrust bearing flange to the gearbox flange.

[Hoghead]

Originally Posted by Jim Cate

much better fuel economy (and that's kinda hard to understand), running at much lower RPM

Jim

I do not get it either however I gave the worst example using torque peak rating.
I wish I could figure out how to post the graphs for both engines

Yanmar recommend running their engines hard which will increase fuel consumption, while Kubota makes no statement at all?

[Jim Cate]

while Kubota makes no statement at all

FWIW, our Nanni/Kubota is now 28 years and ~4600 hours old. We cruise at 1800-2000 rpm (red line 2800) and have run at similar speeds in neutral for charging for several hundred of those hours. No smoke, no measurable oil consumption, starts on first poke... I'm pretty sure that this sort of engine will be more durable and more forgiving than the Yanmar turbo.

Jim

PS 43 hp in a fairly slippery boat, ~ 11 tonnes cruise weight, and our long term fuel consumption is ~2.6 L/hr.

[jimbunyard]

Originally Posted by Hoghead

I do not get it either however I gave the worst example using torque peak rating.
I wish I could figure out how to post the graphs for both engines

Yanmar recommend running their engines hard which will increase fuel consumption, while Kubota makes no statement at all?

Take a screenshot, then copy and paste the screenshot. I don't know if you can do it from a phone...





Yanmar 4JH110

[Hoghead]

that is the 90T (turbo)
Attached is the 90 NA

[jimbunyard]

The added expense and complexity of a turbo for 10 more foot pounds of torque? I don't get it...

[Hoghead]

Originally Posted by jimbunyard

The added expense and complexity of a turbo for 10 more foot pounds of torque? I don't get it...

And the NA is cheaper
Beta will not sell the 90 NA to me if I am a USA registered boat as it does not meet the appropriate pollution standards. Luckily I am not US registered