why are new motors so quiet?

[MM2SS]

What makes the new motors so quiet? It has to be more than better sound proofing in the cowl. Other than the obvious of bad crank or rod bearings why are the older motors much louder. "new technology" is not the answer that I'm looking for. My 15 mariner is not bad- tolerable. My 125 Force way too loud but runs excellent. Last night I was fishing on a small, very quiet Wisconsin lake and when I turned around to get something, there was wardens boat so close that it startled me. I said "wow are you ever quiet!" She started laughing and said "yeah these new motors are great!" Why is that? What did they change?

 

[BuzzStPoint]

Re: why are new motors so quiet?

Overall the 2 strokes are quieter. But this is sorry to say, Technology. Tighter tollerances, compressions, and exhaust ports have all changed since the 60 and 70s.

Now you mentioned the wardens boats. If you are talking about the DNR, and their big outboards like they have here. they have that are super quiet and barely hear run.
Those are 4 stroke engines, almost like a car engine. In a sense think of it this way, your riding lawn mower is noisy and people can hear it for a block. Fire up your car and your neighbors can't hear it.

 

[fucawi]

Re: why are new motors so quiet?

cus they is 4 stroke

 

[roscoe]

Re: why are new motors so quiet?

cus they is 4 stroke

Disgusting, isn't it?

No roar of the engine.
No 2-stroke oil aroma.

 

[MM2SS]

Re: why are new motors so quiet?

Ok Point Boy wins. cuz dey is four strokes = new tennology...we knew that

"closer tolerances" got me thinking though...

years ago my brother had to machine some pistons for Merc Marine and the unique thing about them was that they were not round. They were a couple of thousanths out of round and I'm thinking now that must have been for piston slap...a noise generator. Probably one of many improvements to quiet them down.

Rosco- why doncha grab a couple of those Tombstones and meet me and Buzz at the Point Brewery to discuss this and other world saving topics further!!!

thanks guys, good fishing!

 

[Frank Acampora]

Re: why are new motors so quiet?

NO--the pistons are "cam ground" oval shaped because in the 2 stroke there is uneven cooling around the cylinders -- the exhaust always is hotter. There is a major diameter and a minor diameter. The piston expands unequally during running to assume a circular shape. There is also a taper, top to bottom since the piston crown expands more than the skirt.

 

[fucawi]

Re: why are new motors so quiet?

on a 2 stroke the fuel is still under pressue and burning when the exhaust port opens ..hence the 2 stroke crackle..on a 4 stroke of course its all enclosed for the burn until the piston pushes the exhaust out ...sale of 2 strokes banned in europe as with oil in the fuel the polution is a problem .