Engine differences?

[legacycycles]

Ive got a 93 zuki dt115. While browsing the parts diagram im noticing that the 140 and 115 share alot of the same parts. Pretty much everything except carbs and intake plate.
Now ive been a life long machanic,just not on outboards,and to think a simple carb change would get 25hp seems huge. Am i missing something or is it this simple?
All the crankcase,cylinder heads,pistons,reeds,rods,ingnition,all the same.Basically anything that would change displacment or HP Is the same part number. What gives?

 

[99yam40]

Re: Engine differences?

just like autos these motors need more fuel and air in and out to get more HP. So I would look at intake, exhaust, carbs, and maybe what controls the timing.
it is cheaper for them to just detune a motor already engineered/designed than to start from scratch

 

[legacycycles]

Re: Engine differences?

just like autos these motors need more fuel and air in and out to get more HP. So I would look at intake, exhaust, carbs, and maybe what controls the timing.
it is cheaper for them to just detune a motor already engineered/designed than to start from scratch

As far as i can everything is the same except the carbs and the plate they bolt to. Ex mani is the same,cdi the same, pretty much everything that would make power except the carbs are the same. It just dosent make sense.

 

[robert graham]

Re: Engine differences?

Maybe the size, shape and position of the intake, transfer and exhaust ports is also different, in addition to the carbs being larger?

 

[legacycycles]

Re: Engine differences?

Maybe the size, shape and position of the intake, transfer and exhaust ports is also different, in addition to the carbs being larger?

All the same part numbers. There is no difference that ive found. Every internall part number is the same with these two engines. As is the cylinder heads and manifolds,reeds,everything.

 

[lakensea]

Re: Engine differences?

Different exhaust tube. Just like on any internal cumbustion engine, change the intake, fuel & exhaust system and you will alter the horsepower output.

 

[legacycycles]

Re: Engine differences?

The ex tube is different as well. But it still seems like a lot HP for carb and ex. But that must be it.

 

[throrope]

Re: Engine differences?

Hulls are rated for max HP. Lakes have max HP limits. Some like four strokes, some like two. Add offshore, short shafts, portables, emissions and you end up with many different needs with little differences in a global economy. Yamaha has 38 different offerings for the US market and next year they will have 38 more. That's a manufacturing nightmare. For us, grouping into families that share platforms similar to the auto industry allows our outboards go the distance through long term parts availability.

Sounds good to me.