I's there a simple way to gain extra power?

[Turin]

I's there a simple way to gain extra power from an outboard motor?

I have tuned up a car engine once.

Is this also posible by an 2stroke outboard?
It needs to get rid of its exhoust gasses and it aint posible to change the exhoust pipe or is this posible?
will the propellor damage if it turns to fast?

 

[finlay]

Re: I's there a simple way to gain extra power?

yes it is there is alot u can do but most of it is not that simple, what sort of motor is it

 

[Scaaty]

Re: I's there a simple way to gain extra power?

They are (2 strokes) pretty well tuned to the max for steady constant under load 3/4/..wide open throttle...ya mess with any exhaust tuning (which is next to impossible), and what ya gain in one spot will just be lost in another. Tossing a set of headers on (impossible) and bigger carbs (where would you get them?) like a car are apples and oranges​

 

[CATransplant]

Re: I's there a simple way to gain extra power?

Easy way? Sure. Buy a bigger outboard.

Modifying two-stroke outboards is way expensive, generally. Racers do it, but it isn't practical for most folks.

 

[larky]

Re: I's there a simple way to gain extra power?

I've heard you can lift the outbourd up on the transon, thus lifting the lower unit out of the water a bit. Which equals less drag. but I'm not sure how much. Probably as much as you can and still keep the water pickup under water. I've never done this so hopfully someone will jump in with some more exerience

 

[tashasdaddy]

Re: I's there a simple way to gain extra power?

with your engine, the AV Plate the flat plate above the propeller, should be about 1 - 1 1/2 inches, above the bottom. you'll have to convert that to metric measurement. thats the simplest. it is not practical to try to get more out of a 2 cycle outboard. as said best is to trade it.

 

[Scaaty]

Re: I's there a simple way to gain extra power?

I've heard you can lift the outbourd up on the transon, thus lifting the lower unit out of the water a bit. Which equals less drag. but I'm not sure how much. Probably as much as you can and still keep the water pickup under water. I've never done this so hopfully someone will jump in with some more exerience

Only works on light boats, high HP motors that can get out of there own way to begin with, and ..(its a long involved story without know what boat/motor we are talking here..)​

 

[kenmyfam]

Re: I's there a simple way to gain extra power?

Easiest way is to buy another motor with a larger number written on it. !!

 

[Dhadley]

Re: I's there a simple way to gain extra power?

There are things you can do to any boat that will help gain efficiency. First we need to know what you have and where you're at. Once you run the numbers to see where your at with the percentage of prop slip then you can make changes. But you have to establish the baseline first.

 

[tashasdaddy]

Re: I's there a simple way to gain extra power?

here's the history: http://forums.iboats.com/showthread.php?t=193037

 

[Turin]

Re: I's there a simple way to gain extra power?

Easiest way is to buy another motor with a larger number written on it. !!

Ive done that all ready.
But my old engine is still slow (5 HP Yamaha).
It seemed like fun to me to make it a bit faster (whithout manny costs ) and than sell it.
But it seams impossible to make it faster so i'll sell it like it is now.

The 25 hp Evinrude is fine my boat is rated at 25 HP so no need for a faster engine.

 

[burroak]

Re: I's there a simple way to gain extra power?

I's there a simple way to gain extra power from an outboard motor?

I have tuned up a car engine once.

Is this also posible by an 2stroke outboard?
It needs to get rid of its exhoust gasses and it aint posible to change the exhoust pipe or is this posible?
will the propellor damage if it turns to fast?

The short answer is, yes; just not cheap.

 

[CATransplant]

Re: I's there a simple way to gain extra power?

Ive done that all ready.
But my old engine is still slow (5 HP Yamaha).

Well, Yamaha has a long, long reputation for getting the most out of 2-stroke engines. My first motorcycle was a 1962 Yamaha YDS-2, a 250cc bike that, even then, put out 30hp. It was a rocket of a bike, long before small bikes had a lot of performance.

Besides that, the engine was reliable.

You can bet that Yamaha squeezed out all the power they could from that little engine, without sacrificing reliability in any way.

Tuning small 2-stroke engines is an art form. I know, because I used to race in the 50cc road racing class back in the 60s. It was always possible to take a 50cc 2-stroke and fiddle it into producing amazing amounts of power, but in a very, very narrow RPM range. I must have made 12 expansion chambers for the little engine on my Benelli. I finally found one that had the engine at pretty much peak performance...at 12,000 RPM. The intake was tuned as well, and the thing had a carburetor on it more suitable for an engine three times its size.

Then there was the fiddling with the ports. I probably threw away half a dozen cylinders trying to get the last .25 hp out of that little tiddler.

It would run reasonably well only at full throttle. It would eat pistons on a regular basis. I could change out a piston in about 15 minutes. Generally, if there was more than one heat in the race, it got a new piston before the next race.

I don't know how much horsepower it produced, since it was never on a dyno, but the little bike was a screamer. I almost won some regional races.

You wouldn't want that engine on your boat. The little Yamaha you're talking about idles. It runs wide open, and every throttle setting in between. It's reliable.

Yes, you could probably squeeze another horsepower or two out of it, but you'd sacrifice something else. That I will guarantee. Yamaha knows what it's doing when it comes to 2-stroke engines, and so do the rest of the manufacturers.

Outboards have long been one of the most innovative applications of 2-stroke technology. Way back in the 40's Evinrude was making a 4-cylinder 5.5 hp outboard, the smallest production 4-cylinder engine ever designed. There are lots of them out there, still pushing small boats alone, mostly at AOMCI meets. Cylinders smaller than I'd believe. Back then, everyone was fiddling with little 2-strokes, trying to get the maximum possible horsepower out of them, while preserving reliability.

There are, to be sure, some detuned outboard models out there. The johnnyrude 9.9 hp models are almost identical with the 15hp model. It's actually possible to convert them. But...why? They cost about the same, even used, and more people want a 9.9 than a 15 these days, due to the many lakes with an "under 10hp" requirement.

Besides, the detuned version seems to last longer, or at least I see a lot more of the older ones on the water.

If you want to try it with your Yamaha, as a fun project, go for it, but I'll be surprised if you get much more out of it. As I said, Yamaha knows 2-strokes pretty darned well.

 

[Turin]

Re: I's there a simple way to gain extra power?

, and more people want a 9.9 than a 15 these days, due to the many lakes with an "under 10hp" requirement.

.

Now I Know the reason why the make 9.9 engine's.

In Holland we don't have an "under 10hp" requirement.
We have speed limmits on the local lake its 6 KMH (dead slow)
So its a bit strange why thy produce engines with 9.9 HP in stead of 10.
But now its all clear.

 

[Turin]

Re: I's there a simple way to gain extra power?

I've sold the engine.

And for good price to so no fun projeckt