power vs displacement?

[jfbiv]

Re: power vs displacement?

G DANE: Was it Johnson/Evinrude or Merc you researched?<br /><br />Thanks

 

[Eldiablo]

Re: power vs displacement?

so, G Dane, if you are refering to mid '80s johnson motors, and i had a 25 power head. From what I read your saying, I could take the lower end from a 35, and a new carb, retime it, and it would meet the specs and have the HP output of a 35. ??<br /><br />and please, I know some of you are looking out for my best interest, but I hardly think that it is cost prihibitive to learn using theory. I have fun whatever I'm doing.

 

[Hooty]

Re: power vs displacement?

I've posted this website location before and some of ya'll may have seen it.It's an animated picture of a running 2 cycl. engine with an expansion chamber. Well worth the trip. You can see what's required to pick-up those last few hp's.<br />Go to : http://w3.one.net/~jschust/animations.html <br /><br />c/6<br /><br />Hooty

 

[G DANE]

Re: power vs displacement?

Eldiablo<br /><br />If you get the leg, lower unit, and intake housing and carb, you got a 35 Hp, Increase ignition advance to 37 btd.<br /><br />jfbiv I only worked on Johnnyrudes.

 

[G DANE]

Re: power vs displacement?

Eldiablo<br /><br />Please be aware, the motor bracket is smaller on 25, but i think it will work - just be sure it sits tight.

 

[G DANE]

Re: power vs displacement?

Whaley<br /><br />You asked why manufacturers let same powerhead produce different torque.<br /><br />Because they are used on boats rated for a max. <br /><br />A motor must produce the rated HP within 10 %<br /><br />I Exa a 20 HP never beyond 22 HP. They have to market a motor to each boat, but its economic to have as many common parts as possible, within a range. Ist not economical to produce a 519 cc 10HP, and it wouldnt run good. The design motor is usually the series biggest HP, as far as I know.

 

[Eldiablo]

Re: power vs displacement?

Thanks G Dane, I will probably never do this unless i run across an incredible deal on a messed up 35, the point of this was to discover how manufacturers can use the same powerhead for such a drestic array of HP sizes. It does seem odd to me that motorcycles are sold by the cc and boats by the hp. I guess it is more odd that motorcycles are sold by cc's though sense you can get such a different power outage. I remember my first cap was a Pinto (you may laugh) and it had a 2.2 engine, and at one point I had a honda with a 2.2 and it had a world more power, upper and lower. I know there are a thoushand reasons why, but in the motorcycle world, they would have been sold as the same. <br /><br />enough of a tangent though....<br /><br />I guess to some up this thread is this....<br /> In some cases you can get (in our case of a 30 to a 35) power increase by changing the carb, which is a very inexpensive venture and 5 more hp on that small an engine is worth it to me, i can't believe anyone would rather spend that money on two cases of beer that would be fleeting.<br /> In some cases yu have to go to quite a bit of trouble and expense by chaning half your outboard in my case, a 25 to a 30, but when I got to a 30, I could change to a 35 with not much more trouble. Makes me want to watch ebay for a cheap 30 or 35 with a siezed powerhead.<br /> In some cases like jfbiv where he has a 25 which is the most standard hp for that block, he is screwed unless he starts going the way of sloopy (boring, nitro), in which case i agree with sloopy and say get a new engine.<br /><br />JB..<br /> you brought in a lot of theory that made me think and improved my knowledge, but you never came close to answering the question.<br /><br />thanks G Dane