90 HP 2 stroke - Add Power

[gregs1]

Anyone know of any mods or aftermarket products that can be added to a 90 HP 2 stroke to gain power?

[jonp]

Hi Greg,

I would be interested in knowing as well. I also have 90HP 2 stroke. I do know that upgrades to the reeds are possible at not too great an expense. Boyeson reeds, I believe. I plan on doing this if I need to remove carbs for cleaning. Anyone else have ideas?

Good Luck
Jon

[Bazooka Joe]

I installed Boyesen reeds in my 04 Yam 90hp 2 strk and thought the reeds were well worth the money (~$85, I think). Basically, all of Boyesen's claims happened- better holeshot, quieter running, better idling & low rpm, and slightly better top end. I'm not sure about fuel economy because I put the reeds into an almost brand new engine.

Now keep in mind, the improvement is not going to be- "WOW,,, Holy cow this thing absolutely RIPS!!!", but rather just a nice noticeable improvement. I found a nice out of the hole power boost for pulling up skiers and it now idles smoothly like a *****ing motor at 650 rpm.

One important note, is that you will probably need to dial in the idle jetting with the fuel screws. These are on the sides of each carb and are hidden behind the stock brass caps. Drill a small hole (just break thru the thin cap approx .020" thk) and insert a small sheet metal screw and yank the cap out with a pliers. The fuel screws will then be right out in the open. If you look on the Yama parts diagrams, you'll see these caps.

Hope this helps and good luck with it.

[Bazooka Joe]

Hey, just wondering if you guys had ever gone for the Boyesen reeds?

[jonp]

Hi Joe,

I have not had a need yet. My 90 runs great (cross my fingers) It idles in gear very smoothly at 600 RPM. Not going to mess with it unless I need to. I did change props to a 19 Black stainless. It Dropped more RPM than I expected form a 17, lost 600RPM. Did you pick up any RPMs when you did the upgrade? If I can squeeze another 200 maybe I will do this.

thx
Jon

[Bazooka Joe]

Jon,

I don't know if I gained a whole bunch on top, maybe a little like a mph or so, but that is more of a function of what boat the motor is pushing. Bigger boat takes a lot more hp to push a couple mph faster. If you have a lighter craft, then you'll probably see more pull on top. Most of the gain I realized, is that now the engine pulls harder at a noticeably lower rpm, helping the holeshot. My idle improved, but it sounds like yours is pretty good too. A 19" prop is probably a lot for the 90 Yam to pull. What rpm are you current turning and is that with a fully loaded boat, or just yourself in the boat?

I have my 90 Yam on a lighter 16' aluminum fish/ski boat. With a 17" Ballistic SS and just me in the boat, I can turn it at 5900 rpm at 43+ mph GPS. For waterskiing, I run a 16" SS and need to watch the tach if doing a full throttle blast.

Joe

[jonp]

Anyone else getting results like this

Hi Joe,

I run a 19 inch K series stainless on 17 ft Boston Whaler (pre 2002 Montauk hull) Hull is fairly light, 950 LBS. With a light load 1/2 tank and just my self, I can squeeze 5200 RPM trimmed out (takes about 15 seconds to get there...) I am guessing 42-43 MPH ?


With a 17p stainless, I get 5700 RPM. Seems to get to 5700 a bit easier. I tried a 3 blade 19 ballistic last season, but too big. I could only get 4900 with a very light load. The ballistic has a sightly larger diameter blades a radical design, may better for a bass boat.

Anyone else getting results like this?

Jon

[jonp]

More Preformance info

Just an added note, Went wake boarding yesterday. Did OK with almost a full tank (20 gals) and 3 adults. Pulled a 180LBS wake boarder up with out too much effort. Was only able to 5000 RPM WOT trimmed out with the 19 SS K series.

Anybody seeing results like this for comparison?

thx
Jon