WW25D (what will 25hp do) contest

[motorpsykler]

OK armchair engineers awhile back I asked how a 25hp Yamaha would do on my new 72 Starcraft SS rated at 85hp. I got some good advice, but now I am asking you to put up a number. Not because I am lazy, but just the opposite, I just finished installing the motor on the Starcraft and am getting ready to take it out. I will be alone in the boat, I figure the foam is saturated and heavy, because I haven't got to it yet and the floor is original. Here is your frame of reference, it's my 75 Lund Pike. It does 23 mph with the 25hp Yamaha:

I now installed that very motor to my 72 Starcraft SS:

Question is, what will she do @ WOT? I will find out in about an hour, I'm taking it out with my GPS and we will see. I will give you guys 24hrs to post your guess, before I reveal the speed. The only prize is bragging rights. Good luck!

....oh yeah, for the record, my guess is 20mph

 

[Rickairmedic]

Re: WW25D (what will 25hp do) contest

Motor I am gonna go with you here I dont think the SS is that much heavier than the Lund so I will say 20 also.


Rick

 

[Kainon]

Re: WW25D (what will 25hp do) contest

18.5

 

[Lil' Rhody]

Re: WW25D (what will 25hp do) contest

22mph....

 

[Landscaping Wiz 808]

Re: WW25D (what will 25hp do) contest

I'll say 17mph as it looks like the Starcraft has more bottom surface area.

Preferred payment is in 2 cycle oil!

BOB

 

[motorpsykler]

Re: WW25D (what will 25hp do) contest

Alright it looks like many didn't want to go "on the record". Here's what happened, and I have to say I am suprised. There was a little wind so I took a two way average like they do at Bonneville. Against the wind, it went 22.8mph and with the wind 23.1mph for a two way average of 22.95 mph. Same top end as the Lund. I did notice a few differences though. The most suprising, to me, was that the motor seemed to over rev on the Starcraft. I don't have a tach on either boat but, I've had the Lund for 5 years so I know it really well. The Yamaha was definately revving higher on the Starcraft. I'm guessing it's a little more efficient while on plane. Maybe I could get a few more mph's with some more pitch? I did notice it dropped off plane sooner than the Lund, I could throttle down to 14mph and still be on plane on that boat. On the Starcraft, it dropped and started plowing just under 18mph. Which, with this motor doesn't give me much range.

Looks like Lil' Rhody came the closest with 22mph, congrats!

 

[Rickairmedic]

Re: WW25D (what will 25hp do) contest

That is rather amazing considering there are guys struggling with 30MPH with twice as much motor .


Rick

 

[Uxboat]

Re: WW25D (what will 25hp do) contest

I ran my 16 foot Jupiter all summer with my 25 hp Mercury,it would plane okay with 2 people and my Lab.It was fine except I worried about running flat out for any lenght of time just pulled it this weekend and mounted a 1977 Mercury 500.With 2 more cylinders and twice the horsepower it should be good to go,all thought I never knew the top speed of the 25 hp I don,t except the 500 will double the top end. Cheers Mike

 

[Landscaping Wiz 808]

Re: WW25D (what will 25hp do) contest

GREAT SCOTT!! That thing did 23mph with a 25 on it? You still have 60hp before you reach your max horsepower! You should buy, borrow or steal (only kidding about that last part) a 85hp to see what that'll do.

While you're at it install a flux capacitor and try to hit 88MPH!

BOB

 

[motorpsykler]

Re: WW25D (what will 25hp do) contest

I ran my 16 foot Jupiter all summer with my 25 hp Mercury,it would plane okay with 2 people and my Lab.It was fine except I worried about running flat out for any lenght of time just pulled it this weekend and mounted a 1977 Mercury 500.With 2 more cylinders and twice the horsepower it should be good to go,all thought I never knew the top speed of the 25 hp I don,t except the 500 will double the top end. Cheers Mike

I worry the same thing about my Yamaha, I pretty much have WOT or just creep along at 6mph, anything in between just works the motor too hard. Don't expect double the top end out of your 50hp, it doesn't work that way. Drag increases at appoximately the square of speed, therefore the horsepower needed to overcome drag is also squared. Rickairmedic is right, 50hp should get you around 29-30mph. From what I've read on here 80-85 horspower gets you in the 37mph range. Which is pretty nice, since it planes around 20mph, thats a 17 mph range.