Marine Overdrive!!! Save fuel like the automobile!

[jacobstrix]

Marine Overdrive System

Just thought I would share this new method for saving fuel using old technology. Sorry for the cross post.

www.marineoverdrive.com/default.aspx

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The fuel economy, or fuel savings was evaluated at gallons per hour at speeds from 22 mph to 55 mph in direct drive versus overdrive. I.E., Gallons per hour usage at 22 mph in direct drive versus gallons per hour usage at 22 mph in overdrive. Gallons per hour usage at 35 mph in direct drive versus gallons per hour usage at 35 mph in overdrive, and so on. The overall fuel savings at 4,200 ft. elevation was 15.7%, the estimated fuel savings at sea level would be in the 20 to 21% range.

 

[DJ]

Re: Marine Overdrive!!! Save fuel like the automobile!

Link is-INOP.

If you're selling-GO elsewhere.

 

[tashasdaddy]

Re: Marine Overdrive!!! Save fuel like the automobile!

years ago, my dad's truck was totaled, it had a 4 speed on the floor manual shift. some how he managed to get that thing into a boat, i was too young to remember much about it, but he loved it.

 

[Mark42]

Re: Marine Overdrive!!! Save fuel like the automobile!

I read the article. It sounds like a basic overdrive unit from the description. Article says it mounts on the bell housing of an i/o.

Claims to save 15 - 17% in tests on his new center console. Claims he spent $50,000 developing the unit ... "most of which it was spent on the new boat and engine he used to test the product" . He bought a 20 ft center console.

Too bad they don't show any photos of the product or boat in action.

 

[Chris1956]

Re: Marine Overdrive!!! Save fuel like the automobile!

Folks, We prop our boats to turn max recommended RPM at WOT. If you were to increase the effective propeller pitch, via greater RPM (ie overdrive) or by shifting the pitch to a higher value, the motor would lug. I therefore think overdrive for boats is usless. If you had a boat that you could not prop to be within Max RPM Range at WOT (ie RPMs too high), the OD unit may have promise.

The shift prop, on the other hand, shifts down to give the boat more initial power. My problem with the shift prop is it's succeptibility to damage when you hit something.

 

[jtexas]

Re: Marine Overdrive!!! Save fuel like the automobile!

why are there no constant speed props for boats?

 

[Mark42]

Re: Marine Overdrive!!! Save fuel like the automobile!

Folks, We prop our boats to turn max recommended RPM at WOT. If you were to increase the effective propeller pitch, via greater RPM (ie overdrive) or by shifting the pitch to a higher value, the motor would lug. I therefore think overdrive for boats is usless. If you had a boat that you could not prop to be within Max RPM Range at WOT (ie RPMs too high), the OD unit may have promise.

.

I had similar thoughts about lugging the boat. But at low rpms, and for non-2 stroke engines, lugging may not be an issue.

 

[Chris1956]

Re: Marine Overdrive!!! Save fuel like the automobile!

JTexas, I think the drag of the boat in the water would make shifting gears non-feasible.

Mark42, All engines can be lugged. For example, sometimes the gas mileage for 5th gear is worse than the gas mileage for the same car in 4th gear. If the car is not going fast enough, placing it in 5th gear (OD) causes it to use more fuel do to lugging it.

Now, If you wanted to use a transmission gears instead of changing props for water skiing, that is a good use.

 

[JB]

Re: Marine Overdrive!!! Save fuel like the automobile!

What the devil is this topic doing in the OUTBOARD Non-repair Forum?

Moving it.

 

[QC]

Re: Marine Overdrive!!! Save fuel like the automobile!

Lugging is not a bad thing if you are looking for fuel economy. You could absolutely use a lower number gear ratio (affect of so called OD) for cruising and result in better fuel economy. Not with all engines and not at all RPM points and especially not all loads, but the fact is that running most engines at a lower RPM for the same load results in better fuel efficiency. This is especially true for throttled engines like most of our I/O engines . . .

Yes, I understand about long term lugging and the negative affect on some engines. However, modern truck engines, including throttled ones like the 8.1 (496), are all setup to be run at full load at much lower RPM than we run marine engines at full load (WOT RPM). It is done for fuel economy, longevity and reducing driver fatigue (less shifting). There is nothing about a marine application that should change that capability except the fact that there are usually no gears . . .

With a transmission I will also retract my previous comments about the relative unimportance of peak torque in a marine application. It is precisely because we do not have gears (or hills) that makes peak torque relatively meaningless in a boat.

 

[Dhadley]

Re: Marine Overdrive!!! Save fuel like the automobile!

A shifting transmission or an overdrive unit on an inboard or I/O is very old technology. Been around for years. V drives were almost always an overdrive unit.

 

[Silvertip]

Re: Marine Overdrive!!! Save fuel like the automobile!

I can envision a CVT with a little less ratio spread than used in cars. With a little overdrive at the top end coupled with the CVT feature, the engine would stay in its power band regardless of load yet provide higher gearing when demands are less.

 

[QC]

Re: Marine Overdrive!!! Save fuel like the automobile!

I can envision a CVT with a little less ratio spread than used in cars. With a little overdrive at the top end coupled with the CVT feature, the engine would stay in its power band regardless of load yet provide higher gearing when demands are less.

Absolutley, 100% correct. The downsides are increased weight, cost and maitenance so don't hold your breath . . .

What would happen is that propshaft RPM would increase without engine speed increasing until the throttle was wide open. Then it would ride right up the full load curve until peak horsepower was developed. This keeps the throttle open under most conditions, which greatly improves fuel economy.

 

[Tail_Gunner]

Re: Marine Overdrive!!! Save fuel like the automobile!

I can envision a CVT with a little less ratio spread than used in cars. With a little overdrive at the top end coupled with the CVT feature, the engine would stay in its power band regardless of load yet provide higher gearing when demands are less.

Absolutley, 100% correct. The downsides are increased weight, cost and maitenance so don't hold your breath . . .

What would happen is that propshaft RPM would increase without engine speed increasing until the throttle was wide open. Then it would ride right up the full load curve until peak horsepower was developed. This keeps the throttle open under most conditions, which greatly improves fuel economy.

I would not be so sure of the weight,cost maintance thing, outdrives are really old tech and very expensive with a lot of maintaince, the cvt's in ford's are only 150-175 lbs (with reverse planteray geare's) 8) as to maintance there are only two cones and a chain. And they are extremely reliable as of yet. I find them to be very exciting there very smooth and deleiver power very efficently.................However merc would loose all the revenue it gets from its current producton and some day there parts business would he shall we say "HIgh&Dry".........

 

[rodbolt]

Re: Marine Overdrive!!! Save fuel like the automobile!

wow I gotta see one on a 33 grady with twins at 4200 when it slaps into a 4 ft swell and almost stalls the engine,
how many of you use overdrive while towing your 30ft travel trailer uphill at 4000 RPM?
most hulls I deal with with gas motors turn between 3500 and 4500 to keep on plane for that 28+ mile run to the gulfstream.
QC I have an 8.1 with 330 hours on it with a detonated piston due to lugging.
it had been propped to turn 3600.
the replacement engine cost the man 15000 and is now propped at 5000.
yall have to remember on a boat the load never goes away. if ya dont belive it run it at WOT and pull the emergency stop lanyard and see how quick it stops.
then do the same speed in your car and kill the ign and see how far it coasts.
lugging a gas motor,especially an EFI can kill it by either detonation or fuel wash. either one shortens engine life.

 

[QC]

Re: Marine Overdrive!!! Save fuel like the automobile!

rodbolt,

Good comments and let me clarify mine:

1) Throttled engines are most efficient at WOT that is a fact.

2) Modern throttled automotive engines have been designed for deep lug conditions

3) Yes, a 4 foot swell is a hill and the benefits in high load factor applications as you note would be lessened.

4) Modern electronics can control fuel delivery as well as gear ratio (CVT). Imagine that Grady with diesels. What happens? The fuel rate is increased as the RPM starts to drop due to the swell, hopefully maintaining close to the original RPM. The ultimate goal is maintaining propshaft speed right? Why then couldn't electronics adjust both the fuel rate and the engine RPM with the combo that Silvertip envisioned resulting in the same propshaft RPM?

5) With an active knock sensor what you describe with that 496 could/should have been prevented.

6) I did not say that you could simply take the existing marine engines, particularly older ones, and simply add a CVT and go. However, newer electronic engines can do a variety of things, like allowing that deep lug condition for a limited time and then raising RPM and closing the throttle a little.

6) I said so called OD for a reason. I don't care if there is a difference between input shaft speed and output shaft speed and how you do it. It could be argued that OD is stupid anyway. In a car you achieve spinning the output shaft speed faster and then reduce it again with the rear-end. So what? The point being that with your trailer example what we care about is engine RPM and road speed. How you do it, OD or not, really doesn't matter if the tranny is capable of the input torque.

7) You're right, load doesn't go away, but the load drops from WOT RPM down linearly with RPM. Current single speed gear setups are only at WOT at max speed and max acceleration. That is sorta stupid.

The discussion was fuel economy and those changes I note would absolutely improve it. Are there other factors? Of course, but there is no automatic barrier to running these engines at reduced RPM and full load though. When I started in the truck engine biz almost 30 years ago we ran the 15 liter engines at 1800 RPM cruise, 2100 max, and rarely let them get below 1500 before down shifting. Now we are specing them to run at 1300 RPM cruise, sometimes1600 RPM max, and don't downshift until 1000 RPM. Things change . . .

 

[Don S]

Re: Marine Overdrive!!! Save fuel like the automobile!

I think this whole topic should have been moved to either the Dockside Chat, or Stupid Human Tricks, not the I/O forum.