Interesting reading in the service manual

[Gary H NC]

I was reading through my manual and noticed my 175 has the same specs as a 200. They have the same size pistons,compression,bore,stroke ect.
So i wonder what gives the 200 the extra power?
Different carbs? Intakes different?
Good question for you Johnny-Rude pros..

OOPS,Should have posted this in the Non repair outboard forum..

 

[Silvertip]

Re: Interesting reading in the service manual

Just like with cars, every manufacturer has two, three, or even four engines based on the same block with varying HP ratings. In four strokes its cam, compression and carburetion (of fuel injection) that determines power output. In two strokes its porting, compression, carburetion and exhaust tuning. Note the "porting" issue. While the bore and stroke of two engines may be the same, porting may not be and that's the "gotcha". Porting an engine requires disassembly and machine work. If you need a 200 you should buy a 200. Upgrading an engine is rarely worth the cost.

 

[Gary H NC]

Re: Interesting reading in the service manual

If i ever need a new powerhead i may go up.
I figured it wasn't simple but was wondering anyway.
The boat is rated for 300 hp,i was dreaming anyway...lol

 

[Dhadley]

Re: Interesting reading in the service manual

The 149 cid 150 and 175 use the same powerhead (block, crank, rods, pistons, heads). The 200 uses a different block, different porting and different heads. All use the same intake, ignition, gear ratio etc. Different carbs. Some of the 150 XP / GT's use 200 port timing and have different heads again. If you ever had to replace the powerhead you could use a 200 but I doubt you'd see any difference. If you wanted to change something I'd look for a set of XP /GT heads. They have a really good swirl pattern.

This is assuming it's on a boat that responds to small increases in torque and it's set up really well now. If it's rated for 300, one thing comes to mind -- E-Tec 250 HO.