Before getting into HP gains have you maximized yourself with proper motor height / set back / propping for what you want to achieve? Are you looking for top end speed or quick hole shots?

They are great motors for sure. You can do a few things. Reeds won't add performance but may enhance reliability as those metal ones are likely getting old. You could try a set of Carbon Fibre Reeds from say Chris Carson Marine. You could find a set of higher compression heads from say hydro tec marine as they are supposed to add a few HP. I think it means changing jetting in your carbs though to do this but the folks at hydro tec can help with that. The biggest carbs Yamaha made for the 2.6L motor are 34 mm (not sure if that was on your motor or not but is on my 200 and 225) however there are after market ones by people like hydro tec and Bob Kottman that modify them to 36 mm. Bigger carbs means bigger power but also means more gas lol!

Another thought might be to say find yourself an old 200 or 225 2.6L if your boat is rated for it as you can get your gain that way. Maybe even find a blown one and rebuild it - this is what I did (I did have lots of help from a friend who knew what they were doing).

I just had my prop cleaned and smoothed at local prop shop. I have no jack plate. Just heard of guys switching the carbs/reeds from a 200+ on my year of motor for quick easy hp gains u can do at home.

Ah, the search for the fountain of youth and free horse power continues.

Some things never change.

yep
back in tha day .
kids would get the latest hotrod magazine and next thing ya know they show up at the shop.
would take an hour or more to talk them out of that lastest rump-de-rump camshaft.


that stock 150 Yamaha can deal with about 6000 RPM reliably.

to make more power your either going to need MORE RPM OR your going to need to change the gear ratio.
you CANNOT simply change something and gain magic speeds.

same with that rumpty rump cam.
now we need more fuel,air,compression,a loser(higher stall speed) torque converter and a rear axle ratio of at least 3.9/1.

speed costs money.
how fast do you wish to go ??

What type of prop do you have? Pitch? Material?

To answer your question about swapping carbs / reeds the 220 excel and 225 motors have a different orientation for the reeds (horizontal) as compared to yours (vertical) up to and including the 200. Presumably Yamaha did this to help with the HP increase. The carb on the 150 for 1990 is a different part number as the 225. Now the other major difference is the electronic ignition on the 225 vs. mechanical timing on the 150. All that along with a tuner adds up to 75 hp. I could be missing something but these are the major differences (and heads as the compression is different on the 225).

I suppose you could mix and match to make a 225 out of a 150 but it is uncharted waters for me. There are lots of guys who know how to unlock HP from these motors but it goes beyond bolt on HP.

Be safe and make sure your hull and transom are sound before you do anything!

yes, what you say is kind of true, but that is assuming it wasn't setup properly in the first place.....it is a simple fact of life, you can't just add more fuel and expect big a HP boost, you have to find a way to get that fuel into the motor to make a bigger bang, and that requires more air too, then find a way to get the "bang" gasses out faster, and so it goes.

As Dubber said....from what I've seen at Hydrostream events the Excel 225 horizontal intake and carbs are the hot ticket. Most opt to run mechanical timing and delete Excel computer and sensors. Less stuff to go wrong.
One thing I'm not sure of is whether the exhaust on the 150 is different than on 200-225. Have to get that additional air/fuel out.....

port timing is entirely different.

my advice is simple.
make sure your current set up is efficient and enjoy it.

From what I understand as well the guys making big power out of carbed 2.6L motors want the mechanical timing as well over the electronic ignition so they can dial things in the way they want it. You can really mess things up though playing with timing :S

I do believe that the tuner (exhaust) is different on the 220 Excel /225 over the 150-200 models. My 225 does have a bit more growly sound than my 200 did.