1992 Yammie 40HP Precision Blend

[bassmani]

i have heard that you can buy the 50HP carbs/kits and put them on the 40HP.
I need little more power to get my 16ft Xpress out of the hole on plane. It is running about 30 miles per hour and i need that extra HP.
Can i do this and what do i need?

thx

 

[99yam40]

Re: 1992 Yammie 40HP Precision Blend

You probably would need the 50 carbs not just some kits. There are different main,pilot, and air jets. Not sure about the main body of carbs.
I think the reeds are different also along with the exhaust.
A motor needs more air and fuel to make HP and you have to allow it to leave without too much back pressure and keep it in tune.
Then you will need a different prop to hook up the extra 10 HP.
Seem like a lot of money to spend on a almost 20 year old motor unless you find a junked 50 around that year

 

[bassmani]

Re: 1992 Yammie 40HP Precision Blend

thanks. Engine runs great. just need that extra HP to get out of plane. with one person, it gets off fine.. with 2 peoplem it takes a good 45 seconds to get off.
its on a 16 ft xpress alum boat and runs at 30mph. Should this run at a higher speed or should i go to a 4 blade prop..

thx

 

[99yam40]

Re: 1992 Yammie 40HP Precision Blend

I can get around 35 on my 16' SV Xpress C40 with just me at 5500RPM. Just takes a few seconds with 2 persons(5 maybe ,never timed it). What prop do you have and what RPMs are you running WOT? You may have a motor problem.

Look at this site and see what props they used and the performance they got.http://www.yamaha-motor.com/outboard/products/perfbull.aspx?ls=outboard

 

[bassmani]

Re: 1992 Yammie 40HP Precision Blend

Thanks. I don't have a TAC on this boat, so i don't know the RPM's that i am getting on WOT.. I am lagging 4-7 MPH at WOT and it may be due to the prop. I would rather have it plane quicker than get extra MPH. If i have a second person get in the middle of the boat on WOT, it planes quicker. Might need the 4 blade prop to accomplish this.

thx

 

[99yam40]

Re: 1992 Yammie 40HP Precision Blend

pull your prop and see what size and pitch you are running.
either you are too heavily loaded for the prop you are running or you have a motor problem, sound to me its the motor but cannot tell until you say what prop you are running.

You meed to find out your WOT RPM, if you cannot get around 5500 you have motor problem or you are over propped.

 

[rodbolt]

Re: 1992 Yammie 40HP Precision Blend

MPH is a teat on a boar hog.
worthless.
gotta know what kind of RPM your turning at WOT.
4 blade props typically go slower,plane slower and eat more fuel.
its called blade drag.

 

[bassmani]

Re: 1992 Yammie 40HP Precision Blend

Hello All,

I figured i would give it a try and believe it or not, a $50.00 hydrofoil fixed this issue. My boat planes with no issues. It actually get's up on plane real fast with 2 people in the boat.
I did lose about 2mph on the top end, but that's ok.

thanks for helping out.