Fish-Hawk.Net

Outboard Transmissions? Idea!

I wasn't sure if I had posted this or not, because I remember having a few discussions about it somewhere! But I didn't see anything on this board so I thought I'de post it anyways. But if I am dragging up a topic that was discussed before I appologize.

With rising fuel costs, many of us are almost always looking for ways to save on gas while pursuing our beloved finned friends. Well I had an idea that could help to solve this problem that starts from ground zero, your outboard. And if it is feasable, you'de almost have to wonder why nobody had thought of this before. Maybe they have been, but aren't saying much untill they find something that works.

The way it stands outboards have 2 gears, FW & REV. Now think about an automobile, with an engine of the same power, we'll say 200HP. There are several reasons that this car can achieve phenominally better mileage, and in turn much faster topend speeds as well. One is friction, a car transfering it's energy from the tires to the road is significantly more efficient than a prop biting into water.

But another thing is the GEARING. Can you imagine how bad of milage your car would get if you always ran it in 1rst or 2nd all the time? And thats assuming you didn't blow your engine either! What I am suggesting is maybe try to apply that technology somehow to outboards. Some kind of small and efficient gearing system which could allow the engine to get the same amount of speed, just at lower RPM's.

Now one problem I had suggested to me is that if you do that it would take too long to get up through the gears so in essence what is the point? It's not going to any more efficient, and you will lose out on acceleration. But my answer was, keep it simple, don't bother with 4 or 5 fw gears, just use 2, high and low. Low for quick holeshots and acceleration and high for when you get out in the open water and really wanna crank up the MPH.

Now again the premise of this idea is not for blazing fast speeds with higher gearing (although that will obviously happen). But the main reason behind this is to get better milage out of your engine. For example, and bare in mind these aren't actual figures, just ones I made up to try and illustrate my point, if you have a 150 outboard with this high/low gearing, you could probably get the same speed in high as a 200HP outboard, but you will in turn will use way less fuel becuase it's a smaller engine. Now again, those are only gestimates, but you can probably see a bit more clearly now where I am going with all this.

Anyone else have any insight to this? Possibe problems, other ideas? I'm looking for a lot of feedback especially from mechanincs who would have a better idea as to exactly how or why this would, or would not work. Thanks

Aric Stoner

You also have a weight and space limitation for outboards.

For now, take a look at DFI engines like the Mercury Optimax that gets 20-30% better fuel economy over it's EFI and 4 stroke cousins.

Grumpy

I have tossed the idea around in my head several times over the years, but for less environmentally sound reasons. Always thought it would be fun to have a clutch and a 4 speed stickshift in a boat. Trashed the idea though when I mentally pictured ripping skiers arms out their sockets shifting from 2nd to 3rd.

I'm interested to see the feedback you get from the mechanical types. I suspect there is a reason it hasn't been done already.

Im with grumpy space and weight followed with cost if it aint broke dont fix it. If you start spinning the props any faster you may get into even more exotic metals for the prop stainless steel or titanium back to cost. then get one off ballance watch out. Yea I know ss props are common but may need better grade (fff any thoughts). Just looked at a johnson 140 4 stroke with a gear ratio of 2.38: 1 and 140 hp at 5900 rpm how fast can you spin a prop before you cavitate it to pieces. Sorry this mechanic thinks no. But keep thinking and asking questions you might just hit on somthing.

I imagine so too lol. Probably for that same reason lol. Another thing might be that when you drop the rpms going into the higher gears wouldn't the nose of your boat shoot up? Maybe, I dunno lol.

Rideaufish,

remember, the whole point of this is not to achieve yet higher speeds therefore requiring stronger props etc. But it is to reduce the fuel consumption by allowing smaller engines to achieve the same speeds as the big 250 brutes that we have now. Like I said, speed isn't the issue, economy is!

in a car 4 th gear is 1:1 so over drive is .9 ish to 1 so the engine turn .9 time to the trans out put of 1 so to get better fuel economy with an outboard you would have to spin the prop faster at the same engine rpms. My guess cavitation would be the limit now if you could have 2 props 1 for hole shots 1 for top end you might have somthing but I think cost is the problem there.

Hmm, I never looked at it like that. But thats why I posted, to get some heads churning out there lol. I am only one man, and while I do have some understanding of how engines work, I'm not a mechanic. Just an idealist with way too much time on my hands lol.