Carb swap possible???

[nehring]

I have a 1999 Yamaha 150 2-stroke. It is the "Plain Jane" model... C150 I think it's called. I was looking at specs and noticed that the 150-175-200 & 225 bore and stroke specs are all the same. What is it that makes these outboards differ in horsepower ratings? The only thing that I can think of is the carburation.<br />If I am correct, could I swap my carbs with those from a 200? Would I then have a 200 horsepower outboard? Or is there more to it then that? I am curious! If this is a true and feasible assumption... what year model 200hp outboard carbs would work on my '99 150?<br />Thanks in advance!<br />Brian

 

[swist]

Re: Carb swap possible???

This has to be in the top 10 most frequently asked questions. The different HP ratings on the same block are usually realized through a combination of things, including carbs or carb jetting, reed valve design, ignition timing, lower unit gearing, fuel pumps, and a number of other things.<br /><br />If it were that easy, everyone would be doing it, but the incremental cost will be high, and the likelyhood of getting it right low.

 

[nehring]

Re: Carb swap possible???

So... from what you are saying... it is very possible to do since the Yamaha's from 150-225hp have the same block, bore and stroke, lower unit constuction and gearing, timing specs and fuel pumps! So getting a set of carbs, reeds and cages from a 200 would bolt right on and be set and jetted to make 200 hp on a 150! Not expensive ($60 for mine)... and the likelyhood of success should be right on the money!<br />I'll slap the setup on this weekend and let you all know the outcome!

 

[JB]

Re: Carb swap possible???

No, Nehring. That is not what swist is saying.<br /><br />Those people go to great lengths to NOT reveal the differences and swapping a bunch of parts will NOT get your 150 to a 200.<br /><br />You will spend an obscene amount of money and be disappointed.

 

[Silvertip]

Re: Carb swap possible???

The carbs are different, jetting is different, exhaust tube is different, porting is different, compression is different, timing is different, and in some cases the lower unit gearing is different which means different props are required. It is inexpensive for the factory to make these changes, but verrrry expensive for the owner to do it. If it were as simple as you think it is, everyone would buy the smaller engine and swap the parts. It simply doesn't work that way. Engine displacement on outboards is no different than on cars. Manufacturers can provide many horsepower ratings from the same block.

 

[jay dezman]

Re: Carb swap possible???

if you do a part by part, p/n comparison you can eliminate some of the potential issues. what you can't easily compare are things like the port timing cast/machined into the block.<br /><br />at $60 i would give it a try, but don't be disappointed....<br /><br />the references to gear ratio's/props alludes to a different (potential) rpm range where peak power will occur, it may be necessary to reduce pitch to get the powerhead into the "new" power range

 

[Ray Neudecker]

Re: Carb swap possible???

It is possible to upgrade to a 200 without the porting through parts swapping. It will require swappping the tuner and exhaust divider as well as the reeds and carbs. You will need to also change the jetting and timing. There is also a lot of labor involved such as pulling the powerhead, exhaust plate and intake.