If you could do it over again?

[Underway]

The cooling water pickoffs on the FL120 supply just barely enough water for one shaft log. Splitting it would invite overheating of both shaft logs.

Also, as was demonstrated and charted by Bob Lowe on the GB owners forum the fuel savings in a boat like ours even with the unpowered prop freewheeling would be minimal to none, depending on the power setting.

As to deliberately running on one to save fuel, while fuel is certainly getting more expensive, compared to all the other costs associated with boating it's still practically free. It's certainly not expensive enough yet to make it worth slowing our glacial 8-knot pace through the water even more just to save a few bucks per trip.

Yes, it a slow flow rate on our boat also...throttled by the size of the small orifice on the heat exchanger tank. Since most boats have ample engine cooling, especially at lower power, it's a simple task to enlarge that bleed orifice. And easy peasy to check it all out with a Harbor Freight heat gun.

I wasn't suggesting that you cruise on one all the time given your previously stated info about the high drag characteristics of the GB 36. I was simply suggesting that free wheeling in the event of a genuine engine failure would save fuel over locking the shaft....and be more safe from the sound of your locking setup. I guess Bob Lowe let it overheat during his testing...which I aim to look up, by the way. Can't beat data for getting a handle on the real deal. And as you know the data show that the economy equation actually likes the remaining engine to run in a higher power band. So pushing up the power on the remaining engine to achieve your normal twin engine speed isn't necessarily a bad thing from the overall MPG perspective. On the other hand, the rudders on those GB look a little on the small size. Anyway, when you get your cooling lines reconfigured, you ought to give it a try...might be surprised how well it works.

 

[Moonstruck]

An economical boat is an oxymoron. It's funny how we spend so much time on ways to cut our fuel costs - is there a target? $100/year, $500, 1,000? How about don't go as far, or as fast?

Moonstruck has two 500 hp engines for a total of 1000 hp. We cruise at 25-27 knots. I won't say that fuel cost is insignificant, but it doesn't come close to the total of all the other costs. Yeah, we could run at displacement speeds or on one engine, but we didn't choose the boat for that. I am still very happy with our choice.

 

[ksanders]

Moonstruck has two 500 hp engines for a total of 1000 hp. We cruise at 25-27 knots. I won't say that fuel cost is insignificant, but it doesn't come close to the total of all the other costs. Yeah, we could run at displacement speeds or on one engine, but we didn't choose the boat for that. I am still very happy with our choice.

I agree

When we had our fast cruiser is was no issue to go spend $750 in fuel for a weekends boating.

We didn't switch to a larger slower boat to save fuel. We switched to gain comfort and to be able to stay onboard for longer periods of time.

I'm not running our boat on one engine either. We can throttle back to a slow cruise and get between 1.75 and 2 nmpg. Thats not bad for moving a three berdroom, two bath house around on the water.

 

[Underway]

An economical boat is an oxymoron. It's funny how we spend so much time on ways to cut our fuel costs - is there a target? $100/year, $500, 1,000? How about don't go as far, or as fast?

How much an individual wants to save, and the options to get there are entirely up to each owner and I don't place a value judgement on their reasons or how they operate their boat. Understanding what is technically possible is interesting and potentially useful if it's supported by data. Discussion is virtually free.

A huge number of owners on the Great Lakes have answered your last question by tying their boats fast to the dock for entire boating season.

 

[angus99]

Are folding or feathering props ever an option on these higher-powered boats, as they were on my recently departed sailboat?

Any thoughts on why folding/feathering props aren't seen on these boats? is it lack of backing ability or are there other factors? Seems like if they were viable, it would eliminate the need to freewheel. Apologies if I missed an earlier answer to this.

 

[FF]

Any thoughts on why folding/feathering props aren't seen on these boats?

They don't seen to hold up as well as a std prp.

If someone has the bucks a CPP (Controlable Pitch Prop) would be the #1 choice.

The sacrifice in the loss due to the larger diameter hub is made up for in operation.

Some folks will use a sail prop for a get home wing engine for a Blue water boat.

 

[angus99]

Any thoughts on why folding/feathering props aren't seen on these boats?

They don't seen to hold up as well as a std prp.

If someone has the bucks a CPP (Controlable Pitch Prop) would be the #1 choice.

The sacrifice in the loss due to the larger diameter hub is made up for in operation.

Some folks will use a sail prop for a get home wing engine for a Blue water boat.

Thanks for the explanation. Seems like a niche there for some entrpreneur.

 

[Marin]

I was simply suggesting that free wheeling in the event of a genuine engine failure would save fuel over locking the shaft....and be more safe from the sound of your locking setup. I guess Bob Lowe let it overheat during his testing...which I aim to look up, by the way.

Our current shaft locking system is great. It was the earlier system that was a bit iffy.

I don't know that Bob's boat had cooling water sent to the shaft logs. It was an Alaskan 45 (wood) with Ammaine engines. Knowing Bob I expect it did not have the shaft log cooling issue. He's not the kind of person that would deliberately allow something to overheat.

 

[Delfin]

Any thoughts on why folding/feathering props aren't seen on these boats? is it lack of backing ability or are there other factors? Seems like if they were viable, it would eliminate the need to freewheel. Apologies if I missed an earlier answer to this.

Other than cost, I can't think of a reason. We cruised with a Max Prop for 20 years (sail) and it was ideal for that, with no discernible (at least to me) reduction in backing ability. One nice thing about the Max Prop, at least according to the manufacturer is that as load changes, the pitch will change kinda sorta like a CPP but at a much lower cost.

 

[markpierce]

What about complication, potential for failure, and additional burden of maintenance cost? Are they 99.99% reliable?

 

[Marin]

What about complication, potential for failure, and additional burden of maintenance cost? Are they 99.99% reliable?

Well, they aren't on the Washington State ferries.

I suspect that the size of props needed to move boats like ours and the power it takes to move them would not lend itself to the use of a simple folding prop where inertia holds it out under reverse. I have seen this kind of prop used on the get-home shafts of Nordhavns in the Seaview Yard but they are very small like the sailboat props.

My guess is that to provide variable pitch and feathering for a boat like ours the prop's pitch mechanism would have to be some sort of a mechanical system either electronically controlled or manual. And this would for sure add to the elements Mark speaks of.

 

[psneeld]

They are out there....

Max-Prop 4 Blade VP Fast - 126mm Hub - 30"
[max126430F] $13,205.00

 

[angus99]

They are out there....

Max-Prop 4 Blade VP Fast - 126mm Hub - 30"
[max126430F] $13,205.00

So, high initial cost vs. fuel savings. I'm waiting for someone to calculate the return on investment crossover point.

 

[Delfin]

What about complication, potential for failure, and additional burden of maintenance cost? Are they 99.99% reliable?

Proven technology used on thousands of boats for a great many years. Hardly a new design.